politicians of our time seem inclined to overrate them. Lord
Brougham, for instance, in his Life of Hume, says, of his
political economy, 'Mr. Hume is, beyond all doubt, the author of
the modern doctrines which now rule the world of science.'
_Brougham's Works_, Glasgow, 1856, vol. ii. p. 176. But so far
from this being the case, the science of political economy has,
since the time of Hume, received such additions, that if that
illustrious philosopher were to rise from the dead, he would
hardly be able to recognize it. To him, many of its largest and
most fundamental principles were entirely unknown. Hume knew
nothing of the causes which govern the accumulation of wealth, and
compel that accumulation to proceed with different speed in
different states of society; a fruitful and important study almost
entirely neglected until entered upon by Rae. Neither did Hume
know anything of the law of the ratio between population and
wages; nor of the ratio between wages and profits. He even
supposes (_Philosophical Works_, vol. iii. p. 299, Edinburgh,
1826) that it is possible for the labouring classes by combination
'to heighten their wages;' and again (p. 319) that the richer a
nation is, and the more trade it has, the easier it will be for a
poor country to undersell its manufactures, because the poor
nation enjoys the advantage of a 'low price of labour.' Elsewhere,
he asserts that coin can be depreciated without raising prices,
and that a country, by taxing a foreign commodity, could increase
its own population. 'Were all our money, for instance, recoined,
and a penny's worth of silver taken from every shilling, the new
shilling would probably purchase every thing that could have been
bought by the old; the prices of every thing would thereby be
insensibly diminished; foreign trade enlivened; and domestic
industry, by the circulation of a great number of pounds and
shillings, would receive some increase and encouragement.'
_Philosophical Works_, vol. iii. p. 324. 'A tax on German linen
encourages home manufactures, and thereby multiplies our people
and industry.' p. 365. These are cardinal errors, which go to the
very root of political economy; and when we fairly estimate what
has been done by Malthus and Ricardo, it will be evident that
Hume's doctrines do not 'rule the world of science.' This is no
disparagement of Hume, who, on the contrary, effected wonderful
things, considering the then state of knowledge. The mistake is,
in imagining that such a rapidly advancing science as political
economy can be governed by doctrines propounded more than a
century ago.
[694] 'Every thing in the world is purchased by labour, and our passions
are the only causes of labour.' _Essay I. on Commerce, in Hume's
Philosophical Works_, vol. iii. p. 294. Hence, he saw the fallacy
of the assertion of the French economists, 'that all taxes fall
ultimately upon land.' p. 388.
[695] 'Money is not, properly speaking, one of the subjects of commerce,
but only the instrument which men have agreed upon to facilitate
the exchange of one commodity for another.' _Essay on Money in
Philosophical Works_, vol. iii. p. 317. 'It is, indeed, evident
that money is nothing but the representation of labour and
commodities, and serves only as a method of rating or estimating
them.' p. 321.
[696] See _Essay V. on the Balance of Trade_, in _Hume's Philosophical
Works_, vol. iii. pp. 348-367.
[697] _Hume's Philosophical Works_, vol. iii. pp. 333-335. Even now, a
knowledge of this truth is so little diffused, that, lately, when
Australia and California began to yield immense quantities of
gold, a notion was widely circulated that the interest of money
would consequently fall; although nothing can be more certain than
that if gold were to become as plentiful as iron, the interest of
money would be unaffected. The whole effect would fall upon price.
The remarks on this subject in _Ritchie's Life of Hume_, London,
1807, pp. 332, 333, are interesting, as illustrating the slow
progress of opinion, and the difficulty which minds, not specially
trained, experience when they attempt to investigate these
subjects.
[698] 'Nothing is more usual, among states which have made some advance
in commerce, than to look on the progress of their neighbours with
a suspicious eye, to consider all trading states as their rivals,
and to suppose that it is impossible for any of them to flourish,
but at their expense. In opposition to this narrow and malignant
opinion, I will venture to assert, that the increase of riches and
commerce in any one nation, instead of hurting, commonly promotes
the riches and commerce of all its neighbours.' ... 'I go farther,
and observe, that where an open communication is preserved among
nations, it is impossible but the domestic industry of every one
must receive an increase from the improvements of the others.'
_Essay on the Jealousy of Trade_, in _Hume's Philosophical Works_,
vol. iii. pp. 368, 369.
[699] This letter, which I have referred to in my first volume, p. 229,
was published, for, I believe, the first time, in 1846, in
_Burton's Life and Correspondence of Hume_, vol. ii. p. 486. It
is, however, very difficult to determine what Adam Smith's opinion
really was upon this subject, and how far he was aware that rent
did not enter into price. In one passage in the _Wealth of
Nations_ (book i. chap. vi. p. 21) he says of wages, profit, and
rent, 'in every society, the price of every commodity finally
resolves itself into some one or other, or all of those three
parts; and _in every improved society, all the three enter, more
or less, as component parts, into the price of the far greater
part of commodities_.' But in book i. chap. xi. p. 61, he says,
'High or low wages and profit are the causes of high or low price;
high or low rent is the effect of it.' This latter opinion we now
know to be the true one; it is, however, incompatible with that
expressed in the first passage. For, if rent is the effect of
price, it cannot be a component of it.
It is very observable, that Hume and Adam Smith, who made such immense
additions to our knowledge of the principles of trade, had no practical
acquaintance with it.[700] Hume had, at an early period of his life, been
in a mercantile house; but he threw up that employment in disgust, and
buried himself in a provincial town, to think, rather than to
observe.[701] Indeed, one of the capital defects of his mind, was a
disregard of facts. This did not proceed, as is too often the case, from
that worst form of moral obliquity, an indifference to truth; since he,
on the contrary, was an ardent lover of it, and was, moreover, a man of
the purest and most exemplary character, utterly incapable of falsehood,
or of prevarication of any kind.[702] In him, a contempt for facts was
merely the exaggerated result of a devotion to ideas. He not only
believed, with perfect justice, that ideas are more important than facts,
but he supposed that they should hold the first place in the order of
study, and that they should be developed before the facts are
investigated. The Baconian philosophy, which, though it allows a
preliminary and tentative hypothesis, strongly insists upon the necessity
of first collecting the facts, and then proceeding to the ideas, excited
his aversion; and this, I have no doubt, is the reason why he, who was
usually so lenient in his judgments, and was so keen an admirer of
intellectual greatness is, nevertheless, grossly unfair towards Bacon,
with whose method it was impossible for him to sympathize, though he
could not deny its utility, in physical science.[703] If Hume had
followed the Baconian scheme, of always rising from particulars to
generals, and from each generalization to that immediately above it, he
would hardly have written one of his works. Certainly, his economical
views would never have appeared, since political economy is as
essentially a deductive science as geometry itself.[704] Reversing the
inductive process, he was in favour of beginning with what he termed
general arguments, by which he hoped to demonstrate the inaccuracy of
opinions which facts were supposed to have proved.[705] He did not stop
to investigate the facts from which the inference had been drawn, but he
inverted the order by which the inference was to be obtained. The same
dislike to make the facts of trade the basis of the science of trade, was
displayed by Adam Smith, who expresses his want of confidence in
statistics, or, as it was then termed, political arithmetic.[706] It is,
however, evident, that statistical facts are as good as any other facts,
and, owing to their mathematical form, are very precise.[707] But when
they concern human actions, they are the result of all the motives which
govern those actions; in other words, they are the result, not merely of
selfishness, but also of sympathy. And as Adam Smith, in the _Wealth of
Nations_, dealt with only one of these passions, namely, selfishness, he
would have found it impossible to conduct his generalization from
statistics, which are necessarily collected from the products of both
passions. Such statistical facts were, in their origin, too complex to be
generalized; especially as they could not be experimented upon, but could
only be observed and arranged. Adam Smith, perceiving them to be
unmanageable, very properly rejected them as the basis of his science,
and merely used them by way of illustration, when he could select what he
liked. The same remark applies to other facts which he drew from the
history of trade, and, indeed, from the general history of society. All
of these are essentially subsequent to the argument. They make the
argument more clear, but not more certain. For, it is no exaggeration to
say, that, if all the commercial and historical facts in the _Wealth of
Nations_ were false, the book would still remain, and its conclusions
would hold equally good, though they would be less attractive. In it,
every thing depends upon general principles, and they, as we have seen,
were arrived at in 1752, that is, twenty-four years before the work was
published in which those principles were applied. They must, therefore,
have been acquired independently of the facts which Adam Smith,
subsequently incorporated with them, and which he learnt during that long
period of twenty-four years. And the ten years which he employed in
composing his great work, were not spent in one of those busy haunts of
men, where he might have observed all the phenomena of industry, and
studied the way in which the operations of trade affect human character,
and are affected by it. He did not resort to one of those vast marts and
emporiums of commerce, where the events were happening which he was
seeking to explain. That was not his method. On the contrary, the ten
years, during which he was occupied in raising to a science the most
active department of life, were passed in complete seclusion in
Kirkaldy, his quiet little birthplace.[708] He had always been remarkable
for absence of mind, and was so little given to observation, as to be
frequently oblivious of what was passing around him.[709] In that
obliviousness, he, amid the tranquil scenes of his childhood, could now
indulge without danger. There, cheered, indeed, by the society of his
mother, but with no opportunity of observing human nature upon a large
scale, and far removed from the hum of great cities, did this mighty
thinker, by the force of his own mind, unravel the numerous and
complicated phenomena of wealth, detect the motives which regulate the
conduct of the most energetic and industrious portion of mankind, and lay
bare the schemes and the secrets of that active life from which he was
shut out, while he, immured in comparative solitude, was unable to
witness the very facts which he succeeded in explaining.
[700] Hence, when the _Wealth of Nations_ appeared, one of our wise men
gravely said that 'Dr. Smith, who had never been in trade, could
not be expected to write well on that subject, any more than a
lawyer upon physic.' See _Boswell's Life of Johnson_, edit.
Croker, 1848, p. 478, where this remark is ascribed to Sir John
Pringle.
[701] 'He was sent to a mercantile house at Bristol in 1734; but he
found the drudgery of this employment intolerable, and he retired
to Rheims.' _Brougham's Life of Hume_, Glasgow, 1856, p. 169. See
also _Ritchie's Life of Hume_, p. 6. In _Roberts' Memoirs of
Hannah More_, 2d ed. 1834, vol. i. p. 16, it is said that 'two
years of his life were spent in a merchant's counting-house in
Bristol, whence he was dismissed on account of the promptitude of
his pen in the correction of the letters intrusted to him to
copy.' The latter part of this story is improbable; the former
part is certainly incorrect; since Hume himself says, 'In 1734, I
went to Bristol, with some recommendations to eminent merchants,
but _in a few months_ found that scene totally unsuitable to me. I
went over to France, with a view of prosecuting my studies in a
country retreat.' _Own Life_, p. v.
[702] What Sir James Mackintosh says of him is only a faint echo of the
general voice of his contemporaries. 'His temper was calm, not to
say cold; but though none of his feelings were ardent, all were
engaged on the side of virtue. He was free from the slightest
tincture of malignity or meanness; his conduct was uniformly
excellent.' _Mackintosh's Memoirs_, vol. ii. p. 162. A greater
than Mackintosh, and a man who knew Hume intimately, expresses
himself in much warmer terms. 'Upon the whole,' writes Adam
Smith,--'Upon the whole, I have always considered him, both in his
lifetime and since his death, as approaching as nearly to the idea
of a perfectly wise and virtuous man as perhaps the nature of
human frailty will permit.' _Hume's Philosophical Works_, vol. i.
p. xxv. Some notices of Hume will be found in an interesting work
just published. _Autobiography of Alexander Carlyle_, Edinburgh,
1860, pp. 272-278. But Carlyle, though a man of considerable
practical skill, was incapable of large views, and was, therefore,
unable, I will not say to measure, but even to conceive, the size
of such an understanding as that possessed by David Hume. Of his
want of speculative power, a decisive instance appears in his
remarks on Adam Smith. He gravely says (_Autobiography_, p. 281),
'Smith's fine writing is chiefly displayed in his book on _Moral
Sentiments_, which is the pleasantest and most eloquent book on
the subject. His _Wealth of Nations_, from which he was judged to
be an inventive genius of the first order, is tedious and full of
repetition. His separate essays in the second volume have the air
of being occasional pamphlets, without much force or
determination. On political subjects, his opinions were not very
sound.' It is rather too much when a village-preacher writes in
this strain of the greatest man his country has ever produced.
[703] He speaks of him in the following extraordinary terms. 'If we
consider the variety of talents displayed by this man; as a public
speaker, a man of business, a wit, a courtier, a companion, an
author, a philosopher; he is justly the object of great
admiration. If we consider him merely as an author and
philosopher, the light in which we view him at present, though
very estimable, _he was yet inferior to his contemporary Galileo,
perhaps even to Kepler_.' ... 'The national spirit which prevails
among the English, and which forms their great happiness, is the
cause why they bestow on all their eminent writers, and on Bacon
among the rest, such praises and acclamations as may often appear
partial and excessive.' _Hume's History of England_, vol. vi. pp.
194, 195, London, 1789.
[704] See the note in vol. i. p. 250, of _Buckle's History of
Civilization_.
[705] Thus, for instance, in his remarkable _Essay on the Balance of
Trade_, he says (_Philosophical Works_, vol. iii. p. 349), 'Every
man who has ever reasoned on this subject, has always _proved his
theory, whatever it was, by facts and calculations_, and by an
enumeration of all the commodities sent to all foreign kingdoms;'
therefore (p. 350), 'It may here be proper to form a general
argument to prove the impossibility of this event, so long as we
preserve our people and our industry.'
[706] 'I have no great faith in political arithmetic.' _Wealth of
Nations_, book iv. chap. v. p. 218.
[707] Indeed, the only possible objection to them is that the language
of their collectors is sometimes ambiguous; so that, by the same
return, one statistician may mean one thing, and another
statistician may mean something quite different. This is well
exemplified in medical statistics; whence several writers,
unacquainted with the philosophy of scientific proof, have
supposed that medicine is incapable of mathematical treatment. In
point of fact, however, the only real impediment is the shameful
state of clinical and pathological terminology, which is in such
confusion as to throw doubt upon all extensive numerical
statements respecting disease.
[708] 'Upon his return to England in the autumn of 1766, he went to
reside with his mother at his native town of Kirkaldy, and
remained there for ten years. All the attempts of his friends in
Edinburgh to draw him thither were vain; and from a kind and
lively letter of Mr. Hume upon the subject, complaining that,
though within sight of him on the opposite side of the Frith of
Forth, he could not have speech of him, it appears that no one was
aware of the occupations in which those years were passed.'
_Brougham's Life of Adam Smith_, p. 189. Occasionally, however, he
saw his literary friends. See _Dugald Stewart's Biographical
Memoirs_, p. 73, Edinb. 1811, 4to.
[709] 'He was certainly not fitted for the general commerce of the
world, or for the business of active life. The comprehensive
speculations with which he had been occupied from his youth, and
the variety of materials which his own invention constantly
supplied to his thoughts, rendered him habitually inattentive to
familiar objects and to common occurrences; and he frequently
exhibited instances of absence, which have scarcely been surpassed
by the fancy of La Bruyère.' _Stewart's Biographical Memoirs_, p.
113. See also _Ramsay's Reminiscences_, 5th edit. Edinb. 1859, p.
236. Carlyle, who knew him well, says, 'he was the most absent man
in company that I ever saw, moving his lips, and talking to
himself, and smiling, in the midst of large companies.'
_Autobiography of the Rev. Alexander Carlyle_, 2nd edit. Edinb.
1860, p. 279.
The same determination to make the study of principles precede that of
facts, is exhibited by Hume in one of his most original works, the
_Natural History of Religion_. In reference to the title of this
treatise, we must observe that, according to the Scotch philosophers, the
natural course of any movement is by no means the same as its actual
course. This discrepancy between the ideal and the real, was the
unavoidable result of their method.[710] For, as they argued deductively
from fixed premisses, they could not take into account the perturbations
to which their conclusions were liable, from the play and friction of the
surrounding society. To do that, required a separate inquiry. It would
have been needful to investigate the circumstances which caused the
friction, and thus prevented the conclusions from being, in the world of
fact, the same as they were in the world of speculation. What we call
accidents, are constantly happening, and they prevent the real march of
affairs from being identical with the natural march. And, as long as we
are unable to predict those accidents, there will always be a want of
complete harmony between the inferences of a deductive science and the
realities of life; in other words, our inferences will tend towards
truth, but never completely attain it.[711]
[710] A Scotch philosopher of great repute, but, as it appears to me, of
ability not quite equal to his repute, has stated very clearly and
accurately this favourite method of his countrymen. 'In examining
the history of mankind, as well as in examining the phenomena of
the material world, when we cannot trace the process by which an
event _has been_ produced, it is often of importance to be able to
show how it _may have been_ produced by natural causes.' ... 'To
this species of philosophical investigation, which has no
appropriated name in our language, I shall take the liberty of
giving the title of _Theoretical_ or _Conjectural History_; an
expression which coincides pretty nearly in its meaning with that
of _Natural History_ as employed by Mr. Hume, and with what some
French writers have called Histoire Raisonnée.' _Dugald Stewart's
Biographical Memoirs_, pp. 48, 49. Hence (p. 53), 'in most cases,
it is of more importance to ascertain the progress that is most
simple, than the progress that is most agreeable to fact; for,
paradoxical as the proposition may appear, it is certainly true,
that _the real progress is not always the most natural_. It may
have been determined by particular accidents, which are not likely
again to occur, and which cannot be considered as forming any part
of that general provision which nature has made for the
improvement of the race.'
[711] Part of this view is well expressed in _Hume's Treatise of Human
Nature_, book iii. part ii. 'This, however, hinders not but that
philosophers may, if they please, extend their reasoning to the
supposed _state of nature_; provided they allow it to be a mere
philosophical fiction, which never had, and never could have, any
reality.' ... 'The same liberty may be permitted to moral, which
is allowed to natural philosophers; and 'tis very usual with the
latter to consider any motion as compounded and consisting of two
parts separate from each other, though, at the same time, they
acknowledge it to be in itself uncompounded and inseparable.'
_Philosophical Works_, vol. ii. p. 263.
With peculiar propriety, therefore, did Hume term his work a _Natural
History of Religion_. It is an admirable specimen of the deductive
method. Its only fault is that he speaks too confidently of the accuracy
of the results to which, on such a subject, that method could attain. He
believed, that, by observing the principles of human nature, as he found
them in his own mind, it was possible to explain the whole course of
affairs, both moral and physical.[712] These principles were to be
arrived at by experiments made on himself; and having thus arrived at
them, he was to reason from them deductively, and so construct the entire
scheme. This he contrasts with the inductive plan, which he calls a
tedious and lingering process; and while others might follow that slow
and patient method of gradually working their way towards first
principles, his project was, to seize them at once, or, as he expresses
himself, not to stop at the frontier, but to march directly on the
capital, being possessed of which, he could gain an easy victory over
other difficulties, and could extend his conquests over the
sciences.[713] According to Hume, we are to reason, not in order to
obtain ideas, but we are to have clear ideas before we reason.[714] By
this means, we arrive at philosophy; and her conclusions are not to be
impugned, even if they do happen to clash with science. On the contrary,
her authority is supreme, and her decisions, being essentially true, must
always be preferred to any generalization of the facts which the external
world presents.[715]
[712] And, conversely, that whatever was 'demonstratively false,' could
'never be distinctly conceived by the mind.' _Philosophical
Works_, vol. iv. p. 33. Here, and sometimes in other passages,
Hume, though by no means a Cartesian, reminds us of Descartes.
[713] 'Here, then, is the only expedient from which we can hope for
success in our philosophical researches, _to leave the tedious,
lingering method_, which we have hitherto followed, and instead of
taking now and then a castle or a village on the frontier, to
march up directly to the capital, or centre of these sciences, to
human nature itself; which, being once masters of, we may every
where else hope for an easy victory. From this station we may
extend our conquests over all those sciences which more
immediately concern human life, and may afterwards proceed, at
leisure, to discover more fully those which are the objects of
pure curiosity.' _Hume's Philosophical Works_, vol. i. p. 8. See
also, in vol. ii. pp. 73, 74, his remarks on the way 'to consider
the matter _à priori_.'
[714] 'No kind of reasoning can give rise to a new idea, such as this of
power is; but wherever we reason, we must antecedently be
possessed of clear ideas, which may be the objects of our
reasoning.' _Hume's Philosophical Works_, vol. i. p. 217. Compare
vol. ii. p. 276, on our arriving at a knowledge of causes 'by a
kind of taste or fancy.' Hence, the larger view preceding the
smaller, and being essentially independent of it, will constantly
contradict it; and he complains, for instance, that 'difficulties,
which seem unsurmountable in theory, are easily got over in
practice.' vol. ii. p. 357; and again, in vol. iii. p. 326, on the
effort needed to 'reconcile reason to experience.' But, after all,
it is rather by a careful study of his works, than by quoting
particular passages, that his method can be understood. In the two
sentences, however, just cited, the reader will see that theory
and reason represent the larger view; while practice and
experience represent the smaller.
[715] ''Tis certainly a kind of indignity to philosophy, whose sovereign
authority ought every where to be acknowledged, to oblige her on
every occasion to make apologies for her conclusions, and justify
herself to every particular art and science, which may be offended
at her. This puts one in mind of a king arraigned for high treason
against his subjects.' _Hume's Philosophical Works_, vol. i.
pp. 318, 319.
Hume, therefore, believed that all the secrets of the external world are
wrapped up in the human mind. The mind was not only the key by which the
treasure could be unlocked; it was also the treasure itself. Learning and
science might illustrate and beautify our mental acquisitions, but they
could not communicate real knowledge; they could neither give the prime
original materials, nor could they teach the design according to which
those materials must be worked.
In conformity with these views, the _Natural History of Religion_ was
composed. The object of Hume in writing it, was, to ascertain the origin
and progress of religious ideas; and he arrives at the conclusion, that
the worship of many Gods must, every where, have preceded the worship of
one God. This, he regards as a law of the human mind, a thing not only
that always has happened, but that always must happen. His proof is
entirely speculative. He argues that the earliest state of man is
necessarily a savage state; that savages can feel no interest in the
ordinary operations of nature, and no desire to study the principles
which govern those operations; that such men must be devoid of curiosity
on all subjects which do not personally trouble them; and that,
therefore, while they neglect the usual events of nature, they will turn
their minds to the unusual ones.[716] A violent tempest, a monstrous
birth, excessive cold, excessive rain, sudden and fatal diseases, are the
sort of things to which the attention of the savage is confined, and of
which alone he desires to know the causes. Directly he finds that such
causes are beyond his control, he reckons them superior to himself, and,
being incapable of abstracting them, he personifies them; he turns them
into deities; polytheism is established; and the earliest creed of
mankind assumes a form which can never be altered, as long as men remain
in this condition of pristine ignorance.[717]
[716] 'A barbarous, necessitous animal (such as a man is on the first
origin of society), pressed by such numerous wants and passions,
has no leisure to admire the regular face of nature, or make
inquiries concerning the cause of those objects to which, from his
infancy, he has been gradually accustomed. On the contrary, the
more regular and uniform, that is the more perfect, nature
appears, the more is he familiarized to it, and the less inclined
to scrutinize and examine it. A monstrous birth excites his
curiosity, and is deemed a prodigy. It alarms him from its
novelty, and immediately sets him a trembling, and sacrificing,
and praying. But an animal complete in all its limbs and organs is
to him an ordinary spectacle, and produces no religious opinion or
affection. Ask him whence that animal arose? He will tell you,
from the copulation of its parents. And these, whence? From the
copulation of theirs. A few removes satisfy his curiosity, and set
the objects at such a distance that he entirely loses sight of
them. Imagine not that he will so much as start the question,
whence the first animal, much less whence the whole system, or
united fabric of the universe arose. Or, if you start such a
question to him, expect not that he will employ his mind with any
anxiety about a subject so remote, so uninteresting, and which so
much exceeds the bounds of his capacity.' _Natural History of
Religion_, in _Hume's Philosophical Works_, vol. iv. p. 439. See
also pp. 463-465.
[717] 'By degrees, the active imagination of men, uneasy in this
abstract conception of objects, about which it is incessantly
employed, begins to render them more particular, and to clothe
them in shapes more suitable to its natural comprehension. It
represents them to be sensible, intelligent beings like mankind;
actuated by love and hatred, and flexible by gifts and entreaties,
by prayers and sacrifices. Hence the origin of religion. And hence
the origin of idolatry, or polytheism.' _Hume's Philosophical
Works_, vol. iv. p. 472. 'The primary religion of mankind arises
chiefly from an anxious fear of future events,' p. 498.
These propositions, which are not only plausible, but which are probably
true, ought, according to the inductive philosophy, to have been
generalized from a survey of facts; that is, from a collection of
evidence respecting the state of religion and of the speculative
faculties among savage tribes. But this, Hume abstains from doing. He
refers to none of the numerous travellers who have visited such people;
he does not, in the whole course of his work, mention even a single book
where facts respecting savage life are preserved. It was enough for him,
that the progress from a belief in many Gods to a belief in one God, was
the natural progress; which is saying, in other words, that it appeared
to his mind to be the natural progress.[718] With that, he was satisfied.
In other parts of his essay, where he treats of the religious opinions
of the ancient Greeks and Romans, he displays a tolerable, though by no
means remarkable, learning; but the passages which he cites, do not refer
to that entirely barbarous society in which, as he supposes, polytheism
first arose. The premisses, therefore, of the argument are evolved out of
his own mind. He reasons deductively from the ideas which his powerful
intellect supplied, instead of reasoning inductively from the facts which
were peculiar to the subject he was investigating.
[718] '_It seems certain, that, according to the natural progress of
human thought_, the ignorant multitude must first entertain some
grovelling and familiar notion of superior powers, before they
stretch their conception to that perfect Being who bestowed order
on the whole frame of nature. _We may as reasonably imagine, that
men inhabited palaces before huts and cottages_, or studied
geometry before agriculture, as assert that the Deity appeared to
them a pure spirit, omniscient, omnipotent, and omnipresent,
before he was apprehended to be a powerful though limited being,
with human passions and appetites, limbs and organs. The mind
rises gradually from inferior to superior. By abstracting from
what is imperfect, it forms an idea of perfection; and slowly
distinguishing the nobler parts of its own frame from the grosser,
it learns to transform only the former, much elevated and refined,
to its divinity. Nothing could disturb this _natural progress of
thought_, but some obvious and invincible argument, which might
immediately lead the mind into the pure principles of theism, and
make it overleap, at one bound, the vast interval which is
interposed between the human and the Divine nature. But though I
allow, that the order and frame of the universe, when accurately
examined, affords such an argument, yet _I can never think_ that
this consideration could have an influence on mankind, when they
formed their first rude notions of religion.' _Natural History of
Religion_, in _Philosophical Works_, vol. iv. p. 438.
Even in the rest of his work, which is full of refined and curious
speculation, he uses facts, not to demonstrate his conclusions, but to
illustrate them. He, therefore, selected those facts which suited his
purpose, leaving the others untouched. And this, which many critics would
call unfair, was not unfair in him; because he believed, that he had
already established his principles without the aid of those facts. The
facts might benefit the reader, by making the argument clearer, but they
could not strengthen the argument. They were more intended to persuade
than to prove; they were rather rhetorical than logical. Hence, a critic
would waste his time if he were to sift them with a minuteness which
would be necessary, supposing that Hume had built an inductive argument
upon them. Otherwise, without going far, it might be curious to contrast
them with the entirely different facts which Cudworth, eighty years
before, had collected from the same source, and on the same subject.
Cudworth, who was much superior to Hume in learning, and much inferior to
him in genius,[719] displayed, in his great work on the _Intellectual
System of the Universe_, a prodigious erudition, to prove that, in the
ancient world, the belief in one God was a prevailing doctrine. Hume, who
never refers to Cudworth, arrives at a precisely opposite conclusion.
Both quoted ancient writers; but while Cudworth drew his inferences from
what he found in those writers, Hume drew his from what he found in his
own mind. Cudworth, being more learned, relied on his reading; Hume,
having more genius, relied on his intellect. Cudworth, trained in the
school of Bacon, first collected the evidence, and then passed the
judgment. Hume, formed in a school entirely different, believed that the
acuteness of the judge was more important than the quantity of the
evidence; that witnesses were likely to prevaricate; and that he
possessed, in his own mind, the surest materials for arriving at an
accurate conclusion. It is not, therefore, strange, that Cudworth and
Hume, pursuing opposite methods, should have obtained opposite results,
since such a discrepancy is, as I have already pointed out, unavoidable,
when men investigate, according to different plans, a subject which, in
the existing state of knowledge, is not amenable to scientific treatment.
[719] Not that he was by any means devoid of genius, though he holds a
rank far below so great and original a thinker as Hume. He had,
however, collected more materials than he was able to wield; and
his work on the _Intellectual System of the Universe_, which is a
treasure of ancient philosophy, is badly arranged, and, in many
parts, feebly argued. There is more real power in his posthumous
treatise on _Eternal and Immutable Morality_.
The length to which this chapter has already extended, and the number of
topics which I have still to handle, will prevent me from examining, in
detail, the philosophy of Reid, who was the most eminent among the
purely speculative thinkers of Scotland, after Hume and Adam Smith,
though, in point of merit, he must be placed far below them. For, he had
neither the comprehensiveness of Smith, nor the fearlessness of Hume. The
range of his knowledge was not wide enough to allow him to be
comprehensive; while a timidity, almost amounting to moral cowardice,
made him recoil from the views advocated by Hume, not so much on account
of their being false, as on account of their being dangerous. It is,
however, certain, that no man can take high rank as a philosopher, who
allows himself to be trammelled by considerations of that kind. A
philosopher should aim solely at truth, and should refuse to estimate the
practical tendency of his speculations. If they are true, let them stand;
if they are false, let them fall. But, whether they are agreeable or
disagreeable, whether they are consolatory or disheartening, whether they
are safe or mischievous, is a question, not for philosophers, but for
practical men. Every new truth which has ever been propounded, has, for a
time, caused mischief; it has produced discomfort, and often unhappiness,
sometimes by disturbing social or religious arrangements, and sometimes
merely by the disruption of old and cherished associations of thought. It
is only after a certain interval, and when the framework of affairs has
adjusted itself to the new truth, that its good effects preponderate; and
the preponderance continues to increase, until, at length, the truth
causes nothing but good. But, at the outset, there is always harm. And,
if the truth is very great, as well as very new, the harm is serious. Men
are made uneasy; they flinch; they cannot bear the sudden light; a
general restlessness supervenes; the face of society is disturbed, or
perhaps convulsed; old interests, and old beliefs, are destroyed, before
new ones have been created. These symptoms are the precursors of
revolution; they have preceded all the great changes through which the
world has passed; and while, if they are not excessive, they forebode
progress, so if they are excessive, they threaten anarchy. It is the
business of practical men to moderate such symptoms, and to take care
that the truths which philosophers discover, are not applied so rashly as
to dislocate the fabric, instead of strengthening it. But the philosopher
has only to discover the truth, and promulgate it; and that is hard work
enough for any man, let his ability be as great as it may. This division
of labour, between thinkers and actors, secures an economy of force, and
prevents either class from wasting its power. It establishes a difference
between science, which ascertains principles, and art, which applies
them. It also recognizes, that the philosopher and the practical man,
having each a separate part to play, each is, in his own field, supreme.
But it is a sad confusion for either to interfere with the other. In
their different spheres, both are independent, and both are worthy of
admiration. Inasmuch, however, as practical men should never allow the
speculative conclusions of philosophers, whatever be their truth, to be
put in actual operation, unless society is, in some degree, ripe for
their reception; so, on the other hand, philosophers are not to hesitate,
and tremble, and stop short in their career, because their intellect is
leading them to conclusions subversive of existing interests. The duty of
a philosopher is clear. His path lies straight before him. He must take
every pains to ascertain the truth; and, having arrived at a conclusion,
he, instead of shrinking from it because it is unpalatable, or because it
seems dangerous, should on that very account, cling the closer to it,
should uphold it in bad repute, more zealously than he would have done in
good repute; should noise it abroad far and wide, utterly regardless what
opinions he shocks, or what interests he imperils; should, on its behalf,
court hostility and despise contempt, being well assured, that, if it is
not true, it will die, but that, if it is true, it must produce ultimate
benefit, albeit unsuited for practical adoption by the age or country in
which it is first propounded.
But Reid, notwithstanding the clearness of his mind and his great powers
of argument, had so little of the real philosophic spirit, that he loved
truth, not for its own sake, but for the sake of its immediate and
practical results. He himself tells us, that he began to study
philosophy, merely because he was shocked at the consequences at which
philosophers had arrived. As long as the speculations of Locke and of
Berkeley were not pushed to their logical conclusions, Reid acquiesced in
them, and they were good in his eyes.[720] While they were safe and
tolerably orthodox, he was not over-nice in inquiring into their
validity. In the hands of Hume, however, philosophy became bolder and
more inquisitive; she disturbed opinions which were ancient, and which it
was pleasant to hold; she searched into the foundation of things, and by
forcing men to doubt and to inquire, she rendered inestimable service to
the cause of truth. But this was precisely the tendency at which Reid was
displeased. He saw that such disturbance was uncomfortable; he saw that
it was hazardous; therefore, he endeavoured to prove that it was
groundless. Confusing the question of practical consequences with the
totally different question of scientific truth, he took for granted that,
because to his age the adoption of those consequences would be
mischievous, they must be false. To the profound views of Hume respecting
causation, he gravely objects, that if they were carried into effect, the
operation of criminal law would be imperilled.[721] To the speculations
of the same philosopher concerning the metaphysical basis of the theory
of contracts, he replies, that such speculations perplex men, and weaken
their sense of duty; they are, therefore, to be disapproved of, on
account of their tendency.[722] With Reid, the main question always is,
not whether an inference is true, but what will happen if it is true. He
says, that a doctrine is to be judged by its fruits;[723] forgetting that
the same doctrine will bear different fruits in different ages, and that
the consequences which a theory produces in one state of society, are
often diametrically opposed to those which it produces in another. He
thus made his own age the standard of all future ones. He also trammelled
philosophy with practical considerations; diverting thinkers from the
pursuit of truth, which is their proper department, into the pursuit of
expediency, which is not their department at all. Reid was constantly
stopping to inquire, not whether theories were accurate, but whether it
was advisable to adopt them; whether they were favourable to patriotism,
or to generosity, or to friendship;[724] in a word, whether they were
comfortable, and such as we should at present like to believe.[725] Or
else, he would take other ground, still lower, and still more unworthy of
a philosopher. In opposing, for instance, the doctrine, that our
faculties sometimes deceive us,--a doctrine which, as he well knew, had
been held by men whose honesty was equal to his own, and whose ability
was superior to his own,--he does not scruple to enlist on his side the
prejudices of a vulgar superstition; seeking to blacken the tenet which
he was unable to refute. He actually asserts, that they who advocate it,
insult the Deity, by imputing to the Almighty that He has lied. Such
being the consequence of the opinion, it of course follows that the
opinion must be rejected without further scrutiny, since, to accept it,
would produce fatal results on our conduct, and would, indeed, be
subversive of all religion, of all morals, and of all knowledge.[726]
[720] 'I once believed this doctrine of ideas so firmly, as to embrace
the whole of Berkeley's system in consequence of it; till, finding
other consequences to follow from it, which gave me more
uneasiness than the want of a material world, it came into my mind
more than 40 years ago, to put the question, What evidence have I
for this doctrine that all the objects of my knowledge are ideas
in my own mind? From that time to the present, I have been
candidly and impartially, as I think, seeking for the evidence of
this principle but can find none, excepting the authority of
philosophers.' _Reid's Essays on the Powers of the Human Mind_,
edit. Edinburgh, 1808, vol. i. p. 172. And, in a letter which he
wrote to Hume in 1763, he, with a simple candour which must have
highly amused that eminent philosopher, confesses that 'your
system appears to me not only coherent in all its parts, but
likewise justly deduced from principles commonly received among
philosophers; principles which I never thought of calling in
question, until the conclusions you draw from them in the
"Treatise on Human Nature" made me suspect them.' _Burton's Life
and Correspondence of Hume_, vol. ii. p. 155.
[721] 'Suppose a man to be found dead on the high-way, his skull
fractured, his body pierced with deadly wounds, his watch and
money carried off. The coroner's jury sits upon the body, and the
question is put, What was the cause of this man's death, was it
accident, or _felo de se_, or murder by persons unknown? Let us
suppose an adept in Mr. Hume's philosophy to make one of the jury,
and that he insists upon the previous question, whether there was
any cause of the event, or whether it happened without a cause.'
_Reid's Essays on the Powers of the Mind_, vol. ii. p. 286.
Compare vol. iii. p. 33: 'This would put an end to all
speculation, as well as to all the business of life.'
[722] 'The obligation of contracts and promises is a matter so sacred,
and of such consequence to human society, that speculations which
have a _tendency to weaken that obligation_, and to perplex men's
notions on a subject so plain and so important, ought to _meet
with the disapprobation of all honest men_. Some such
speculations, I think, we have in the third volume of Mr. Hume's
"Treatise of Human Nature," and in his "Enquiry into the
Principles of Morals;" and my design in this chapter is, to offer
some observations on the nature of a contract or promise, and on
two passages of that author on this subject. I am far from saying
or thinking, that Mr. Hume meant to weaken men's obligations to
honesty and fair dealing, or that he had not a sense of these
obligations himself. It is not the man I impeach, but his
writings. Let us think of the first as charitably as we can, while
we freely examine the import and _tendency_ of the last.' _Reid's
Essays on the Powers of the Mind_, vol. iii. p. 444. In this, as
in most passages, the italics are my own.
[723] 'Without repeating what I have before said of causes in the first
of these Essays, and in the second and third chapters of this, I
shall here mention some of the consequences that may be justly
deduced from this definition of a cause, that we may judge of it
by its fruits.' _Reid's Essays_, vol. iii. p. 339.
[724] 'Bishop Berkeley surely did not duly consider that it is by means
of the material world that we have any correspondence with
thinking beings, or any knowledge of their existence, and that by
depriving us of the material world, he deprived us at the same
time of family, friends, country, and every human creature; of
every object of affection, esteem or concern, except ourselves.
The good bishop surely never intended this. He was too warm a
friend, too zealous a patriot, and too good a Christian to be
capable of such a thought. _He was not aware of the consequences
of his system_' (poor, ignorant Berkeley), 'and therefore they
ought not to be imputed to him; but we must impute them to the
system itself. It stifles every generous and social principle.'
_Reid's Essays_, vol. ii. pp. 251, 252.
[725] In his _Essays_, vol. i. p. 179, he says of Berkeley, one of the
deepest and most unanswerable of all speculators, 'But there is
one _uncomfortable consequence_ of his system which he seems not
to have attended to, and from which it will be found difficult, if
at all possible, to guard it.'
[726] 'This doctrine is dishonourable to our Maker, and lays a foundation
for universal scepticism. It supposes the Author of our being to
have given us one faculty on purpose to deceive us, and another by
which we may detect the fallacy, and find that he imposed upon
us.' ... 'The genuine dictate of our natural faculties is the
voice of God, no less than what he reveals from heaven; and to say
that it is fallacious, is to impute a lie to the God of truth.'
... 'Shall we impute to the Almighty what we cannot impute to a
man without a heinous affront? Passing this opinion, therefore, as
shocking to an ingenuous mind, and, in its consequences,
subversive of all religion, all morals, and all knowledge,' &c.
_Reid's Essays_, vol. iii. p. 310. See also vol. i. p. 313.
In 1764, Reid published his _Inquiry into the Human Mind_; and in that,
and in his subsequent work, entitled _Essays on the Powers of the Mind_,
he sought to destroy the philosophy of Locke, Berkeley, and Hume. And as
Hume was the boldest of the three, it was chiefly his philosophy which
Reid attacked. Of the character of this attack, some specimens have just
been given; but they rather concern his object and motives, while what we
have now to ascertain is, his method, that is, the tactics of his
warfare. He clearly saw, that Hume had assumed certain principles, and
had reasoned deductively from them to the facts, instead of reasoning
inductively from the facts to them. To this method, he strongly, and
perhaps fairly, objects. He admits that Hume had reasoned so accurately,
that if his principles were conceded, his conclusions must likewise be
conceded.[727] But, he says, Hume had no right to proceed in such a
manner. He had no right to assume principles, and then to argue from
them. The laws of nature were to be arrived at, not by conjecturing in
this way, but by a patient induction of facts.[728] Discoveries depended
solely on observation and experiment; and any other plan could only
produce theories, ingenious, perhaps, and plausible, but quite
worthless.[729] For, theory should yield to fact, and not fact to
theory.[730] Speculators, indeed, might talk about first principles, and
raise a system by reasoning from them. But, the fact was, that there was
no agreement as to how a first principle was to be recognized; since a
principle which one man would deem self-evident, another would think it
necessary to prove, and a third would altogether deny.[731]
[727] 'His reasoning appeared to me to be just; there was, therefore, a
necessity to call in question the principles upon which it was
founded, or to admit the conclusion.' _Reid's Inquiry into the
Human Mind_, p. v. 'The received doctrine of ideas is the
principle from which it is deduced, and of which, indeed, it seems
to be a just and natural consequence.' p. 53. See also _Reid's
Essays_, vol. i. pp. 199, 200, vol. ii. p. 211.
[728] 'The laws of nature are the most general facts we can discover in
the operations of nature. Like other facts, they are not to be hit
upon by a happy conjecture, but justly deduced from observation.
Like other general facts, they are not to be drawn from a few
particulars, but from a copious, patient, and cautious induction.'
_Reid's Inquiry into the Human Mind_, pp. 262, 263.
[729] 'Such discoveries have always been made by patient observation, by
accurate experiments, or by conclusions drawn by strict reasoning
from observations and experiments; and such discoveries have
always tended to refute, but not to confirm, the theories and
hypotheses which ingenious men had invented.' _Reid's Essays_,
vol. i. p. 46.
[730] 'This is Mr. Hume's notion of a cause.' ... 'But theory ought to
stoop to fact, and not fact to theory.' _Reid's Essays_, vol. iii.
p. 276.
[731] 'But yet there seems to be great difference of opinions among
philosophers about first principles. What one takes to be
self-evident, another labours to prove by arguments, and a third
denies altogether.' _Reid's Essays_, vol. ii. p. 218. 'Mr. Locke
seems to think first principles of very small use.' p. 219.
The difficulties of deductive reasoning are here admirably portrayed. It
might have been expected, that Reid would have built up his own
philosophy according to the inductive plan, and would have despised that
assumption of first principles, with which he taunts his opponents. But
it is one of the most curious things in the history of metaphysics, that
Reid after impeaching the method of Hume, follows the very same method
himself. When he is attacking the philosophy of Hume, he holds deduction
to be wrong. When he is raising his own philosophy, he holds it to be
right. He deemed certain conclusions dangerous, and he objects to their
advocates, that they argued from principles, instead of from facts: and
that they assumed themselves to be in possession of the first principles
of truth, although people were not agreed as to what constituted a first
principle. This is well put, and hard to answer. Strange, however, to
say, Reid arrives at his own conclusions, by assuming first principles to
an extent far greater than had been done by any writer on the opposite
side. From them, he argues; his whole scheme is deductive; and his works
scarcely contain a single instance of that inductive logic, which, when
attacking his opponents, he found it convenient to recommend. It is
difficult to conceive a better illustration of the peculiar character of
the Scotch intellect in the eighteenth century, and of the firm hold,
which, what may be called, the anti-Baconian method, had upon that
intellect. Reid was a man of considerable ability, of immaculate honesty,
and was deeply convinced that it was for the good of society that the
prevailing philosophy should be overthrown. To the performance of that
task, he dedicated his long and laborious life; he saw that the
vulnerable point of the adverse system was its method; he indicated the
deficiencies of that method, and declared, perhaps wrongly, but at all
events sincerely, that it could never lead to truth. Yet, and
notwithstanding all this, such was the pressure of the age in which he
lived, and so completely did the force of circumstances shape his
understanding, that, in his own works, he was unable to avoid that very
method of investigation which he rebuked in others. Indeed, so far from
avoiding it, he was a slave to it. The evidence of this I will now give,
because, besides its importance for the history of the Scotch mind, it is
valuable as one of many lessons, which teach us how we are moulded by the
society which surrounds us; how even our most vigorous actions are
influenced by general causes of which we are often ignorant, and which
few of us care to study; and, finally, how lame and impotent we are,
when, as individuals, we try to stem the onward current, resisting the
great progress instead of aiding it, and vainly opposing our little
wishes to that majestic course of events, which admits of no
interruption, but sweeps on, grand and terrible, while generation after
generation passes away, successively absorbed in one mighty vortex.
Directly Reid, ceasing to refute the philosophy of Hume, began to
construct his own philosophy, he succumbed to the prevailing method. He
now assures us, that all reasoning must be from first principles, and
that, so far from reasoning to those principles, we must at once admit
them, and make them the basis of all subsequent arguments.[732] Having
admitted them, they become a thread to guide the inquirer through the
labyrinth of thought.[733] His opponents had no right to assume them, but
he might do so, because to him they were intuitive.[734] Whoever denied
them, was not fit to be reasoned with.[735] Indeed, to investigate them,
or to seek to analyze them, was wrong as well as foolish, because they
were part of the constitution of things; and of the constitution of
things no account could be given, except that such was the will of
God.[736]
[732] 'All reasoning must be from first principles; and for first
principles no other reason can be given but this, that, by the
constitution of our nature, we are under a necessity of assenting
to them.' _Reid's Inquiry_, p. 140. 'All reasoning is from
principles.' ... 'Most justly, therefore, do such principles
disdain to be tried by reason, and laugh at all the artillery of
the logician when it is directed against them.' p. 372. 'All
knowledge got by reasoning must be built upon first principles.'
_Reid's Essays_, vol. ii. p. 220. 'In every branch of real
knowledge there must be first principles, whose truth is known
intuitively, without reasoning, either probable or demonstrative.
They are not grounded on reasoning, but all reasoning is grounded
on them.' p. 360.
[733] 'For, when any system is grounded upon first principles, and
deduced regularly from them, we have a thread to lead us through
the labyrinth.' _Reid's Essays_, vol. ii. p. 225.
[734] 'I call these "first principles," because they _appear to me_ to
have in themselves an intuitive evidence which _I cannot resist_.'
_Reid's Essays_, vol. iii. p. 375.
[735] 'If any man should think fit to deny that these things are
qualities, or that they require any subject, _I leave him to enjoy
his opinion, as a man who denies first principles, and is not fit
to be reasoned with_.' _Reid's Essays_, vol. i. p. 38.
[736] 'No other account can be given of the constitution of things, but
the will of Him that made them.' _Reid's Essays_, vol. i. p. 115.
As Reid obtained his first principles with such ease, and as he carefully
protected them by forbidding any attempt to resolve them into simpler
elements, he was under a strong temptation to multiply them almost
indefinitely, in order that, by reasoning from them, he might raise a
complete and harmonious system of the human mind. To that temptation he
yielded with a readiness, which is truly surprising, when we remember how
he reproached his opponents with doing the same thing. Among the numerous
first principles which he assumes, not only as unexplained, but as
inexplicable, are the belief in Personal Identity;[737] the belief in the
External World;[738] the belief in the Uniformity of Nature;[739] the
belief in the Existence of Life in Others;[740] the belief in
Testimony;[741] also in the power of distinguishing truth from
error,[742] and even in the correspondence of the face and voice to the
thoughts.[743] Of belief generally, he asserts that there are many
principles,[744] and he regrets that any one should have rashly attempted
to explain them.[745] Such things are mysterious, and not to be pried
into. We have also other faculties, which being original and
indecomposable, resist all inductive treatment, and can neither be
resolved into simpler elements, nor referred to more general laws. To
this class, Reid assigns Memory,[746] Perception,[747] Desire of
Self-Approbation,[748] and not only Instinct, but even Habit.[749] Many
of our ideas, such as those concerning Space and Time, are equally
original;[750] and other first principles there are, which have not been
enunciated, but from which we may reason.[751] They, therefore, are the
major premisses of the argument; no reason having yet been given for
them, they must be simple; and not having yet been explained, they are,
of course, inexplicable.[752]
[737] _Reid's Essays_, vol. i. pp. 36, 37, 340, 343, vol. ii. p. 245.
[738] _Reid's Essays_, vol. i. pp. 115, 116, 288-299, vol. ii. p. 251.
[739] Or, as he expresses it, 'our belief of the continuance of the laws
of nature.' _Reid's Inquiry_, pp. 426-435; also his _Essays_, vol.
i. p. 305, vol. ii. p. 268.
[740] _Reid's Essays_, vol. ii. p. 259.
[741] _Reid's Inquiry_, p. 422; and his _Essays_, vol. ii. p. 266.
[742] 'Another first principle is, "That the natural faculties by which
we distinguish truth from error are not fallacious."' _Reid's
Essays_, vol. ii. p. 256.
[743] 'Another first principle I take to be, "That certain features of
the countenance, sounds of the voice, and gestures of the body,
indicate certain thoughts and dispositions of mind."' _Reid's
Essays_, vol. ii. p. 261. Compare his _Inquiry_, p. 416.
[744] 'We have taken notice of several original principles of belief in
the course of this inquiry; and when other faculties of the mind
are examined, we shall find more, which have not occurred in the
examination of the five senses.' _Reid's Inquiry_, p. 471.
[745] 'And if no philosopher had attempted to define and explain belief,
some paradoxes in philosophy, more incredible than ever were
brought forth by the most abject superstition, or the most frantic
enthusiasm, had never seen the light.' _Reid's Inquiry_, p. 45.
[746] _Reid's Essays_, vol. i. p. 329, 334, vol. ii. p. 247.
[747] _Reid's Essays_, vol. i. pp. 9, 71, 303, 304.
[748] _Reid's Essays_, vol. ii. p. 60.
[749] 'I see no reason to think, that we shall ever be able to assign
the physical cause, either of instinct, or of the power of habit.
Both seem to be parts of our original constitution. Their end and
use is evident; but we can assign no cause of them, but the will
of Him who made us.' _Reid's Essays_, vol. iii. p. 119.
[750] 'I know of no ideas or notions that have a better claim to be
accounted simple and original, than those of space and time.'
_Reid's Essays_, vol. i. p. 354.
[751] 'I do not at all affirm that those I have mentioned are all the
first principles from which we may reason concerning contingent
truths. Such enumerations, even when made after much reflection,
are seldom perfect.' _Reid's Essays_, vol. ii. p. 270.
[752] 'Why sensation should compel our belief of the present existence of
the thing, memory a belief of its past existence, and imagination
no belief at all, _I believe no philosopher can give a shadow of
reason_, but that such is the nature of these operations. They are
all simple and original, and _therefore inexplicable_ acts of the
mind.' _Reid's Inquiry_, p. 40. 'We can _give no reason_ why the
retina is, of all parts of the body, the only one on which
pictures made by the rays of light cause vision; and _therefore we
must resolve this solely into a law of our constitution_' p. 258.
All this is arbitrary enough. Still, in justice to Reid, it must be said,
that, having made these assumptions, he displayed remarkable ability in
arguing from them, and that, in attacking the philosophy of his time, he
subjected it to a criticism, which has been extremely serviceable. His
lucidity, his dialectic skill, and the racy and masculine style in which
he wrote, made him a formidable opponent, and secured to his objections
a respectful hearing. To me, however, it appears, that notwithstanding
the attempts, first of M. Cousin, and afterwards of Sir William Hamilton,
to prop up his declining reputation, his philosophy, as an independent
system, is untenable, and will not live. In this I may be mistaken; but
what is quite certain is, that nothing can be more absurd than to
suppose, as some have done, that he adopted the inductive, or, as it is
popularly called, Baconian method. Bacon, indeed, would have smiled at
such a disciple, assuming all sorts of major premisses, taking general
principles for granted with the greatest recklessness, and reserving his
skill for the task of reasoning from propositions for which he had no
evidence, except that on a cursory, or, as he termed it, a common-sense,
inspection, they appeared to be true.[753] This refusal to analyze
preconceived notions, comes under the head of what Bacon stigmatized as
the _anticipatio naturæ_, and which he deemed the great enemy of
knowledge, on account of the dangerous confidence it places in the
spontaneous and uncorrected conclusions of the human mind. When,
therefore, we find Reid holding up the Baconian philosophy, as a pattern
which it behoves all inquirers to follow;[754] and when we, moreover,
find Dugald Stewart, who, though a somewhat superficial thinker, was, at
all events, a careful writer, supposing that Reid had followed it,[755]
we meet with fresh proof of how difficult it was for Scotchmen of the
last age to imbibe the true spirit of inductive logic, since they
believed, that a system which flagrantly violated its rules, had been
framed in strict accordance with them.
[753] In a recent work of distinguished merit, an instance is given of
the loose manner in which he took for granted that certain
phenomena were ultimate, in order that, instead of analyzing them,
he might reason from them. 'Dr. Reid has no hesitation in classing
the voluntary command of our organs, that is, the sequence of
feeling and action implied in all acts of will, among instincts.
The power of lifting a morsel of food to the mouth, is, according
to him, an instinctive or pre-established conjunction of the wish
and the deed; that is to say, the emotional state of hunger,
coupled with the sight of a piece of bread, is associated, through
a primitive link of the mental constitution, with the several
movements of the hand, arm, and mouth, concerned in the act of
eating. _This assertion of Dr. Reid's may be simply met by
appealing to the facts._ It is not true that human beings possess,
at birth, any voluntary command of their limbs whatsoever. A babe
of two months old cannot use its hands in obedience to its
desires. The infant can grasp nothing, hold nothing, can scarcely
fix its eyes on anything.' ... 'If the more perfect command of our
voluntary movements implied in every art be an acquisition, so is
the less perfect command of these movements that grows upon a
child during the first year of life.' _Bain on the Senses and the
Intellect_, London, 1855, pp. 292, 293.
[754] See _Reid's Inquiry_, pp. 436, 446, as well as other parts of his
works: see also an extract from one of his letters to Dr. Gregory,
in _Stewart's Biographical Memoirs_, p. 432.
[755] 'The idea of prosecuting the study of the human mind on a plan
analogous to that which had been so successfully adopted in
physics by the followers of Lord Bacon, if not first conceived by
Dr. Reid, was, at least, first carried successfully into execution
in his writings.' _Stewart's Biographical Memoirs_, p. 419. 'The
influence of the general views opened in the _Novum Organon_, may
be traced in almost every page of his writings; and, indeed, the
circumstance by which they are so strongly and characteristically
distinguished, is that they exhibit the first systematical attempt
to exemplify, in the study of human nature, the same plan of
investigation which conducted Newton to the properties of light,
and to the law of gravitation.' p. 421. From this passage one
might hazard a supposition that Dugald Stewart did not understand
Bacon much better than he did Aristotle or Kant. Of the two last
most profound thinkers, he certainly knew little or nothing,
except what he gathered secondhand. Consequently, he underrates
them.
Leaving mental philosophy, I now come to physical science, in which, if
anywhere, we might expect that the inductive plan would predominate, and
would triumph over the opposite, or deductive, one. How far this was the
case, I will endeavour to ascertain, by an examination of the most
important discoveries which have been made by Scotchmen concerning the
organic and inorganic world. And, as my object is merely to indicate the
turn and character of the Scotch mind, I shall avoid all details
respecting the practical effects of those discoveries, and shall confine
myself to such a narration as will exhibit their purely scientific
aspect, so as to enable the reader to understand what additions were
made to our knowledge of the laws of nature, and in what way the
additions were made. The character of each discovery, and its process,
will be stated, but nothing more. Neither here, nor in any part of this
Introduction, do I pretend to investigate questions of practical utility,
or to trace the connexion between the discoveries of science and the arts
of life. That I shall do in the body of the work itself, where I hope to
explain a number of minute social events, many of which are regarded as
isolated, if not incongruous. For the present, I solely aim at those
broad principles, which, by marking out the epochs of thought, underlie
the whole fabric of society, and which must be clearly apprehended before
history can cease to be a mere empirical assemblage of facts, of which
the scientific basis being unsettled, the true order and coherence must
be unknown.
Among the sciences which concern the inorganic world, the laws of heat
occupy a conspicuous place. On the one hand, they are connected with
geology, being intimately allied, and, indeed, necessarily bound up, with
every speculation respecting the changes and present condition of the
crust of the earth. On the other hand, they touch the great questions of
life, both animal and vegetable; they have to do with the theory of
species, and of race; they modify soil, food, and organization; and to
them we must look for valuable help towards solving those great problems
in biology, which, of late years, have occupied the attention of the
boldest and most advanced philosophers.
Our present knowledge of the laws of heat, may be briefly stated as
branching into five fundamental divisions. These are: latent heat;
specific heat; the conduction of heat; the radiation of heat; and,
finally, the undulatory theory of heat; by which last, we are gradually
discarding our old material views, and are accustoming ourselves to look
upon heat as simply one of the forms of force, all of which, such as
light, electricity, magnetism, motion, gravitation, and chemical
affinity, are constantly assuming each other's shape, but, in their total
amount, are incapable either of increase or of diminution.[756] This
grand conception, which is now placing the indestructibility of force on
the same ground as the indestructibility of matter, has an importance far
above its scientific value, considerable as that undoubtedly is. For, by
teaching us, that nothing perishes, but that, on the contrary, the
slightest movement of the smallest body, in the remotest region, produces
results which are perpetual, which diffuse themselves through all space,
and which, though they may be metamorphosed, cannot be destroyed, it
impresses us with such an exalted idea of the regular and compulsory
march of physical affairs, as must eventually influence other and higher
departments of inquiry. Our habits of thought are so connected and
interwoven, that notions of law and of the necessary concatenation of
things, can never be introduced into one field of speculation, without
affecting other fields which lie contiguous to it. When, therefore, the
modern doctrine of conservation of force,[757] becomes firmly coupled
with the older doctrine of conservation of matter, we may rest assured
that the human mind will not stop there, but will extend to the study of
Man, inferences analogous to those already admitted in the study of
Nature. Having once recognized that the condition of the material
universe, at any one moment, is simply the result of every thing which
has happened at all preceding moments, and that the most trivial
disturbance would so violate the general scheme, as to render anarchy
inevitable, and that, to sever from the total mass even the minutest
fragment, would, by dislocating the structure, bury the whole in one
common ruin, we, thus admitting the exquisite adjustment of the different
parts, and discerning, too, in the very beauty and completeness of the
design, the best proof that it has never been tampered with by the
Divine Architect, who called it into being, in whose Omniscience both
the plan, and the issue of the plan, resided with such clearness and
unerring certainty, that not a stone in that superb and symmetrical
edifice has been touched since the foundation of the edifice was laid,
are, by ascending to this pitch and elevation of thought, most assuredly
advancing towards that far higher step, which it will remain for our
posterity to take, and which will raise their view to so commanding a
height, as to insure the utter rejection of those old and eminently
irreligious dogmas of supernatural interference with the affairs of life,
which superstition has invented, and ignorance has bequeathed, and the
present acceptance of which betokens the yet early condition of our
knowledge, the penury of our intellectual resources, and the inveteracy
of the prejudices in which we are still immersed.
[756] The theory of the indestructibility of force has been applied to
the law of gravitation by Professor Faraday, in his _Discourse on
the Conservation of Force_, 1857; an essay full of thought and
power, and which should be carefully studied by every one who
wishes to understand the direction which the highest speculations
of physical science are now taking. I will quote only one passage
from the opening, to give the reader an idea of its general scope,
irrespective of the more special question of gravitation. 'The
progress of the strict science of modern times has tended more and
more to produce the conviction that force can neither be created
nor destroyed; and to render daily more manifest the value of the
knowledge of that truth in experimental research.' ... 'Agreeing
with those who admit the conservation of force to be a principle
in physics, as large and sure as that of the indestructibility of
matter, or the invariability of gravity, I think that no
particular idea of force has a right to unlimited or unqualified
acceptance, that does not include assent to it.'
[757] As an illustration of this doctrine, I cannot do better than quote
the following passage from one of the most suggestive and clearly
reasoned books which has been written in this century by an
English physicist: 'Wave your hand; the motion which has
apparently ceased, is taken up by the air, from the air by the
walls of the room, &c., and so by direct and reacting waves,
continually comminuted, but never destroyed. It is true that, at a
certain point, we lose all means of detecting the motion, from its
minute subdivision, which defies our most delicate means of
appreciation, but we can indefinitely extend our power of
detecting it accordingly as we confine its direction, or increase
the delicacy of our examination. Thus, if the hand be moved in
unconfined air, the motion of the air would not be sensible to a
person at a few feet distant; but if a piston of the same extent
of surface as the hand be moved with the same rapidity in a tube,
the blast of air may be distinctly felt at several yards'
distance. There is no greater absolute amount of motion in the air
in the second than in the first case, but its direction is
restrained, so as to make its means of detection more facile. By
carrying on this restraint, as in the air-gun, we get a power of
detecting the motion, and of moving other bodies at far greater
distances. The puff of air which would in the air-gun project a
bullet a quarter of a mile, if allowed to escape without its
direction being restrained, as by the bursting of a bladder, would
not be perceptible at a yard's distance, though the same absolute
amount of motion be impressed on the surrounding air.' _Grove's
Correlation of Physical Forces_, London, 1855, pp. 24, 25. In a
work now issuing from the press, and still unfinished, it is
suggested, with considerable plausibility, that Persistence of
Force would be a more accurate expression than Conservation of
Force. See Mr. Herbert Spencer's _First Principles_, London, 1861,
p. 251. The title of this book gives an inadequate notion of the
importance of the subjects with which it deals, and of the reach
and subtlety of thought which characterize it. Though some of the
generalizations appear to me rather premature, no well-instructed
and disciplined intellect can consider them without admiration of
the remarkable powers displayed by their author.
It is, therefore, natural, that the physical doctrine of
indestructibility applied to force as well as to matter, should be
essentially a creation of the present century, notwithstanding a few
allusions made to it by some earlier thinkers, all of whom, however,
groped vaguely, and without general purpose. No preceding age was bold
enough to embrace so magnificent a view as a whole, nor had any preceding
philosophers sufficient acquaintance with nature to enable them to defend
such a conception, even had they desired to entertain it. Thus, in the
case now before us, it is evident, that while heat was believed to be
material, it could not be conceived as a force, and therefore no one
could grasp the theory of its metamorphosis into other forces; though
there are passages in Bacon which prove that he wished to identify it
with motion. It was first necessary to abstract heat into a mere property
or affection of matter, and there was no chance of doing this until heat
was better understood in its immediate antecedents, that is, until, by
the aid of mathematics, its proximate laws had been generalized. But,
with the single exception of Newton, whose efforts, notwithstanding his
gigantic powers, were, on this subject, very unsatisfactory, and who,
moreover, had a decided leaning towards the material theory, no one
attempted to unravel the mathematical laws of heat till the latter half
of the eighteenth century, when Lambert and Black began the career which
Prevost and Fourier followed up. The mind, having been so slow in
mastering the preliminaries and outworks of the inquiry, was not ripe for
the far more difficult enterprise of idealizing heat itself, and so
abstracting it, as to strip it of its material attributes, and leave it
to nothing but the speculative notion of an immaterial force.
From these considerations, which were necessary to enable the reader to
appreciate the value of what was done in Scotland, it will be seen how
essential it was that the laws of the movement of heat should be studied
before its nature was investigated, and before the emission theory could
be so seriously attacked as to allow of the possibility of that great
doctrine of the indestructibility of force, which, I make no doubt, is
destined to revolutionize our habits of thought, and to give to future
speculations a basis infinitely wider than any previously known. In
regard to the movements of heat, we owe the laws of conduction and of
radiation chiefly to France and Geneva, while the laws of specific heat,
and those of latent heat, were discovered in Scotland. The doctrine of
specific heat, though interesting, has not the scientific importance
which belongs to the other departments of this great subject; but the
doctrine of latent heat is extremely curious, not only in itself, but
also on account of the analogies it suggests with various branches of
physical inquiry.
What is termed latent heat, is exhibited in the following manner. If, in
consequence of the application of heat, a solid passes into a liquid, as
ice, for instance, into water, the conversion occupies a longer time than
could be explained by any theory which had been propounded down to the
middle of the eighteenth century. Neither was it possible to explain how
it is, that ice never rises above the temperature of 32° until it is
actually melted, no matter what the heat of the adjacent bodies may be.
There were no means of accounting for these circumstances. And though
practical men, being familiar with them, did not wonder at them, they
caused great astonishment among thinkers, who were accustomed to analyze
events, and to seek a reason for common and every-day occurrences.
Soon after the middle of the eighteenth century, Black, who was then one
of the professors in the University of Glasgow, turned his attention to
this subject.[758] He struck out a theory which, being eminently
original, was violently attacked, but is now generally admitted. With a
boldness and reach of thought not often equalled, he arrived at the
conclusion, that whenever a body loses some of its consistence, as in the
case of ice becoming water, or water becoming steam, such body receives
an amount of heat which our senses, though aided by the most delicate
thermometer, can never detect. For, this heat is absorbed; we lose all
sight of it, and it produces no palpable effect on the material world,
but becomes, as it were, a hidden property. Black, therefore, called it
latent heat, because, though we conceive it as an idea, we cannot trace
it as a fact. The body is, properly speaking, hotter; and yet its
temperature does not rise. Directly, however, the foregoing process is
inverted, that is to say, directly the steam is condensed into water, or
the water hardened into ice, the heat returns into the world of sense; it
ceases to be latent, and communicates itself to the surrounding objects.
No new heat has been created; it has, indeed, appeared and disappeared,
so far as our senses are concerned; but our senses were deceived, since
there has, in truth, been neither addition nor diminution.[759] That
this remarkable theory paved the way for the doctrine of the
indestructibility of force, will be obvious to whoever has examined the
manner in which, in the history of the human mind, scientific conceptions
are generated. The process is always so slow, that no single discovery
has ever been made, except by the united labours of several successive
generations. In estimating, therefore, what each man has done, we must
judge him, not by the errors he commits, but by the truths he propounds.
Most of his errors are not really his own. He inherits them from his
predecessors; and if he throws some of them off, we should be grateful,
instead of being dissatisfied that he has not rejected all. Black, no
doubt, fell into the error of regarding heat as a material substance,
which obeys the laws of chemical composition.[760] But this was merely an
hypothesis, which was bequeathed to him, and with which the existing
state of thought forced him to encumber his theory. He inherited the
hypothesis, and could not get rid of his troublesome possession. The real
service which he rendered is, that, in spite of that hypothesis, which
clung to him to the last, he, far more than any of his contemporaries,
contributed towards the great conception of idealizing heat, and thus
enabled his successors to admit it into the class of immaterial and
supersensual forces. Once admitted into that class, the list of forces
became complete; and it was comparatively easy to apply to the whole body
of force, the same notion of indestructibility, which had previously been
applied to the whole body of matter. But it was hardly possible to effect
this object, while heat stood, as it were, midway between force and
matter, yielding opposite results to different senses; amenable to the
touch, but invisible to the eye. What was wanting, was to remove it
altogether out of the jurisdiction of the senses, and to admit that,
though we experience its effects, we can only conceive its existence.
Towards accomplishing this, Black took a prodigious stride. Unconscious,
perhaps, of the remote tendency of his own labours, he undermined that
doctrine of material heat, which he seemed to support. For, by his
advocacy of latent heat, he taught that its movements constantly baffle,
not only some of our senses, but all of them; and that, while our
feelings make us believe that heat is lost, our intellect makes us
believe that it is not lost. Here, we have apparent destructibility, and
real indestructibility. To assert that a body received heat without its
temperature rising, was to make the understanding correct the touch, and
defy its dictates. It was a bold and beautiful paradox, which required
courage as well as insight to broach, and the reception of which marks an
epoch in the human mind, because it was an immense step towards
idealizing matter into force. Some, indeed, have spoken of invisible
matter; but that is a contradiction in terms, which will never be
admitted, as long as the forms of speech remain unchanged. Nothing can be
invisible, except force, mind, and the Supreme Cause of all. We must,
therefore, ascribe to Black the signal merit that he first, in the study
of heat, impeached the authority of the senses, and thereby laid the
foundation of every thing which was afterwards done. Besides the relation
which his discovery bears to the indestructibility of force, it is also
connected with one of the most splendid achievements effected by this
generation in inorganic physics; namely, the establishment of the
identity of light and heat. To the senses, light and heat, though in some
respects similar, are in most respects dissimilar. Light, for instance,
affects the eye, and not the touch. Heat affects the touch, but, under
ordinary circumstances, does not affect the eye. The capital difference,
however, between them is, that heat, unlike light, possesses the property
of temperature; and this property is so characteristic, that until our
understandings are invigorated by science, we cannot conceive heat
separated from temperature, but are compelled to confuse one with the
other. Directly, however, men began to adopt the method followed by
Black, and were resolved to consider heat as supersensual, they entered
the road which led to the discovery of light and heat being merely
different developments of the same force. Ignoring the effects of heat on
themselves, or on any part of the creation, which was capable of feeling
its temperature, and would therefore be deceived by it, nothing was left
for them to do, but to study its effects on the inanimate world. Then,
all was revealed. The career of discovery was fairly opened; and
analogies between light and heat, which even the boldest imagination had
hardly suspected, were placed beyond a doubt. To the reflection of heat,
which had been formerly known, were now added the refraction of heat, its
double refraction, its polarization, its depolarization, its circular
polarization, the interference of its rays, and their retardation; while,
what is more remarkable than all, the march of our knowledge on these
points was so swift, that before the year 1836 had come to a close, the
chain of evidence was completed by the empirical investigations of Forbes
and Melloni, they themselves little witting that every thing which they
accomplished was prepared before they were born, that they were but the
servants and followers of him who indicated the path in which they trod,
and that their experiments, ingenious as they were, and full of resource,
were simply the direct practical consequence of one of those magnificent
ideas which Scotland has thrown upon the world, and the memory of which
is almost enough so to bribe the judgment, as to tempt us to forget,
that, while the leading intellects of the nation were engaged in such
lofty pursuits, the nation itself, untouched by them, passed them over
with cold and contemptuous indifference, being steeped in that deadening
superstition, which turns a deaf ear to every sort of reason, and will
not hearken to the voice of the charmer, charm he never so wisely.
[758] He was appointed professor in 1756; and 'it was during his
residence in Glasgow, between the years 1759 and 1763, that he
brought to maturity those speculations concerning the combination
of heat with matter, which had frequently occupied a portion of
his thoughts.' _Thomson's History of Chemistry_, vol. i. pp. 319,
320.
[759] _Black's Lectures on Chemistry_, vol. i. pp. 116, 117; and in
various places. Dr. Robison, the editor of these Lectures, says,
p. 513, 'Nothing could be more simple than his doctrines of latent
heat. The experience of more than a century had made us consider
the thermometer as a sure and accurate indicator of heat, and of
all its variations. We had learned to distrust all others. Yet, in
the liquefaction and vaporization of bodies, we had proofs
uncontrovertible of the entrance of heat into the bodies. And we
could, by suitable processes, get it out of them again. Dr. Black
said that it was concealed in them,--_latent_,--it was as much
concealed as carbonic acid is in marble, or water in zeolite,--it
was concealed till Dr. Black detected it. He called it Latent
Heat. He did not mean by this term that it was a different kind of
heat from the heat which expanded bodies, but merely that it was
concealed from our sense of heat, and from the thermometer.' See
also p. xxxvii.: 'Philosophers had long been accustomed to
consider the thermometer as the surest means for detecting the
presence of heat or fire in bodies, and they distrusted all
others.'
[760] 'Fluidity is the consequence of a certain combination of calorific
matter with the substance of solid bodies,' &c. _Black's
Lectures_, vol. i. p. 133. Compare p. 192, and the remarks in
_Turner's Chemistry_, 1847, vol. i. p. 31, on Black's views of the
'chemical combination' of heat. Among the backward chemists, we
still find traces of the idea of heat obeying chemical laws.
By thus considering the descent and relationship of scientific
conceptions, we can alone understand what we really owe to Black's
discovery of latent heat. In regard to the method of the discovery,
little need be said, since every student of the Baconian philosophy must
see, that the discovery was of a kind for which none of the maxims of
that system had provided. As latent heat escapes the senses, it could not
obey the rules of a philosophy, which grounds all truth on observation
and experiment. The subject of the inquiry being supersensual, there was
no scope for what Bacon called crucial experiments and separations of
nature. The truth was in the idea; experiments, therefore, might
illustrate it, might bring it up to the surface, and so enable men to
grasp it, but could not prove it. And this, which appears on the very
face of the discovery, is confirmed by the express testimony of Dr.
Thomson, who knew Black, and was, indeed, one of the most eminent of his
pupils. We are assured by this unimpeachable witness, that Black, about
the year 1759 began to speculate concerning heat; that the result of
those speculations was the theory of latent heat; that he publicly taught
that theory in the year 1761; but that the experiments which were
necessary to convince the world of it were not made till 1764,[761]
though, as I need hardly add, according to the inductive method, it was a
breach of all the rules of philosophy to be satisfied with the theory
three years before the experiments were made, and it was a still greater
breach, not only to be satisfied with it, but to have openly promulgated
it as an original and unquestionable truth, which explained, in a new
manner, the economy of the material world.
[761] 'So much was he convinced of this, that he taught the doctrine in
his lectures in 1761, before he had made a single experiment on
the subject.' ... 'The requisite experiments were first attempted
by Dr. Black in 1764.' _Thomson's History of Chemistry_, vol. i.
p. 324. See also pp. 319, 320; and on the history of the idea in
Black's mind as early as the year 1754, see the interesting
extracts from his note-books in Robison's appendix to _Black's
Lectures_, vol. i pp. 525, 526.
The statement of Dr. Thomson refers to the completion, or last
stage, of the discovery, namely the vaporific combination of heat.
But from a letter which Black wrote to Watt in 1780 (_Muirhead's
Life of Watt_, London, 1859, p. 303), it appears that Thomson has
even understated the question, and that Black, instead of first
teaching his theory in 1761, taught it three years earlier, that
is, _six_ years before the decisive experiments were made. 'I
began,' writes Black, 'to give the doctrine of latent heat in my
lectures at Glasgow in the winter 1757-58, which, I believe, was
the first winter of my lecturing there; or if I did not give it
that winter, I certainly gave it in the 1758-59; and I have
delivered it every year since that time in my winter lectures,
which I continued to give at Glasgow until winter 1766-67, when I
began to lecture in Edinburgh.'
The intellect of Black belonged to a class, which, in the eighteenth
century, was almost universal in Scotland, but was hardly to be found in
England, and which, for want of a better word, we are compelled to call
deductive, though fully admitting that even the most deductive minds have
in them a large amount of induction, since, indeed, without induction,
the common business of life could not be carried on. But for the purposes
of scientific classification, we may say, that a man or an age is
deductive, when the favourite process is reasoning from principles
instead of reasoning to them, and when there is a tendency to underrate
the value of specific experience. That this was the case with the
illustrious discoverer of latent heat, we have seen, both from the nature
of the discovery, and from the decisive testimony of his friend and
pupil. And a further confirmation may be found in the circumstance, that,
having once propounded his great idea, he, instead of instituting a long
series of laborious experiments, by which it might be verified in its
different branches, preferred reasoning from it according to the general
maxims of dialectic; pushing it to its logical consequences, rather than
tracking it into regions where the senses might either confirm or refute
it.[762] By following this process of thought, he was led to some
beautiful speculations, which are so remote from experience, that even
now, with all the additional resources of our knowledge, we cannot tell
whether they are true or false. Of this kind were his views respecting
the causes of the preservation of man, whose existence would, he thought,
be endangered, except for the power which heat possesses of lying latent
and unobserved. Thus, for example, when a long and severe winter was
followed by sudden warmth, it appeared natural that the ice and snow
should melt with corresponding suddenness; and if this were to happen,
the result would be such terrible inundations, that it would be hardly
possible for man to escape from their ravages. Even if he escaped, his
works, that is, the material products of his civilization, would perish.
From this catastrophe, nothing saves him but the latent power of heat.
Owing to this power, directly the ice and snow begin to melt at their
surface, the heat enters their structure, where a large part of it
remains in abeyance, and thus losing much of its power, the process of
liquefaction is arrested. This dreadful agent is lulled, and becomes
dormant. It is weakened at the outset of its career, and is laid up, as
in a storehouse, from which it can afterwards emerge, gradually, and with
safety to the human species.[763]
[762] And he distinctly states that, even in other matters, when he did
make experiments, their object was to confirm theory, and not to
suggest it. Thus, to give one of many instances, in his
_Lectures_, vol. i. p. 354, he says, respecting salts, 'When we
examine the solidity of this reasoning by an experiment, _we have
the pleasure to find facts agree exactly with the theory_.'
[763] See a good summary of this idea in _Black's Lectures on
Chemistry_, vol. i. p. 118. Contrasting his theory of heat with
that previously received, he says, 'But, were the ice and snow to
melt as suddenly as they must necessarily do, were the former
opinion of the action of heat in melting them well founded, the
torrents and inundations would be incomparably more irresistible
and dreadful. They would tear up and sweep away every thing, and
that so suddenly, that mankind should have great difficulty to
escape from their ravages.'
In this way, as summer advances, a vast magazine of heat is accumulated,
and is preserved in the midst of water, where it can do man no injury,
since, indeed, his senses are unable to feel it. There the heat remains
buried, until, in the rotation of the seasons, winter returns, and the
waters are congealed into ice. In the process of congelation, that
treasury of heat, which had been hidden all the summer, reappears; it
ceases to be latent; and now, for the first time, striking the senses of
man, it tempers, on his behalf, the severity of winter. The faster the
water freezes, the faster the heat is disengaged; so that, by virtue of
this great law of nature, cold actually generates warmth, and the
inclemency of every season, though it cannot be hindered, is softened in
proportion as the inclemency is more threatening.[764]
[764] 'Dr. Black quickly perceived the vast importance of this
discovery; and took a pleasure in laying before his students a
view of the extensive and beneficial effects of this habitude of
heat in the economy of nature. He made them remark how, by this
means, there was accumulated, during the summer season, a vast
magazine of heat, which, by gradually emerging, during
congelation, from the water which covers the face of the earth,
serves to temper the deadly cold of winter. Were it not for this
quantity of heat, amounting to 145 degrees, which emerges from
every particle of water as it freezes, and which diffuses itself
through the atmosphere, the sun would no sooner go a few degrees
to the south of the equator, than we should feel all the horrors
of winter.' _Robison's Preface to Black's Lectures_, vol. i.
p. xxxviii.
Thus, again, inasmuch as heat becomes latent, and flies from the senses,
not only when ice is passing into water, but also when water is passing
into steam, we find in this latter circumstance, one of the reasons why
man and other animals can live in the tropics, which, but for this, would
be deserted. They are constantly suffering from the heat which is
collected in their bodies, and which, considered by itself, is enough to
destroy them. But this heat causes thirst, and they consequently swallow
great quantities of fluid, much of which exudes through the pores of the
skin in the form of vapour. And as, according to the theory of latent
heat, vapour cannot be produced without a vast amount of heat being
buried within it, such vapour absorbs and carries off from the body,
that which, if left in the system, would prove fatal. To this we must
add, that, in the tropics, the evaporation of water is necessarily rapid,
and the vapour which is thus produced, becomes another storehouse of
heat, and a vehicle by which it is removed from the earth, and prevented
from unduly interfering with the economy of life.[765]
[765] As I am writing an account of Black's views, and not a criticism
of them, I shall give them, without comment, in his own words, and
in the words of one of his pupils. 'Here we can also trace another
magnificent train of changes, which are nicely accommodated to the
wants of the inhabitants of this globe. In the equatorial regions,
the oppressive heat of the sun is prevented from a destructive
accumulation by copious evaporation. The waters, stored with their
vaporific heat, are thus carried aloft into the atmosphere, till
the rarest of the vapour reaches the very cold regions of the air,
which immediately forms a small portion of it into a fleecy cloud.
This also further tempers the scorching heat by its opacity,
performing the acceptable office of a screen. From thence the
clouds are carried to the inland countries, to form the sources in
the mountains, which are to supply the numberless streams that
water the fields. And, by the steady operation of causes, which
are tolerably uniform, the greater part of the vapours pass on to
the circumpolar regions, there to descend in rains and dews; and
in this beneficent conversion into rain, by the cold of those
regions, each particle of steam gives up the 700 or 800 degrees of
heat which were latent in it. These are immediately diffused, and
soften the rigour of those less comfortable climates.' ... 'I am
persuaded that the heat absorbed in spontaneous evaporation
greatly contributes to enable animals to bear the heat of the
tropical climates, where the thermometer frequently continues to
show the temperature of the human body. Such heats, indeed, are
barely supportable, and enervate the animal, making it lazy and
indolent, indulging in the most relaxed postures, and avoiding
every exertion of body or mind. The inhabitants are induced to
drink large draughts of diluting liquors, which transude through
their pores most copiously, carrying off with them a vast deal of
this troublesome and exhausting heat. There is in the body itself
a continual laboratory, or manufacture of heat, and, were the
surrounding air of such a temperature as not to carry it off, it
would soon accumulate so as to destroy life. The excessive
perspiration, supplied by diluting draughts, performs the same
office as the cold air without the tropics, in guarding us from
this fatal accumulation.' _Black's Lectures_, vol. i. pp. xlvi.
214.
From these and many other arguments, all of which were so essentially
speculative, and dealt with such hidden processes of nature, that even
now we are not justified either in confidently admitting them or in
positively denying them, Black was led to that great doctrine of the
indestructibility of heat,[766] which, as I have pointed out, has, in its
connexion with the indestructibility of force, a moral and social
importance even superior to its scientific value. Though the evidence of
which he was possessed was far more scanty than what we now have, he, by
the reach of his commanding intellect, rather than by the number and
accuracy of his facts, became so penetrated with a conviction of the
stability of physical affairs, that he not only applied that idea to the
subtle phenomena of heat, but, what was much harder to do, he applied it
to cases in which heat so entirely escapes the senses, that man has no
cognizance of it, except through the medium of the imagination. According
to his view, heat passes through an immense variety of changes, during
which it appears to be lost; changes which no eye can ever see, which no
touch can ever experience, and which no instrument can ever measure.
Still, and in the midst of all these changes, it remains intact. From it
nothing can be taken, and to it nothing can be added. In one of those
fine passages of his Lectures, which, badly reported as they are,[767]
bear the impress of his elevated genius, Black, after stating what would
probably happen, if the total amount of heat existing in the world were
to be diminished, proceeds to speculate on the consequences of its being
increased. Were it possible for any power to add to it ever so little,
it would at once overstep its bounds; the equilibrium would be disturbed;
the framework of affairs would be disjointed. The evil rapidly
increasing, and acting with accumulated force, nothing would be able to
stop its ravages. It must continue to gain ground, till all other
principles are absorbed and conquered. Sweeping on, unhindered, and
irresistible, before it, every animal must perish, the whole vegetable
world must disappear, the waters must pass into vapour, and the solid
parts of the globe be merged and melted, until, at length, the glorious
fabric, loosened and dissolved, would fall away, and return to that
original chaos out of which it had been evolved.[768]
[766] See his strong protest against the notion that heat is ever
destroyed, in his _Lectures_, vol. i. pp. 125, 126, 164, 165.
[767] They were published after his death from such scanty materials,
that their editor, Dr. Robison, says (_Preface to Black's
Lectures_, vol. i. p. x.): 'When I then entered seriously on the
task, I found that the notes were (with the exception of perhaps a
score of lectures) in the same imperfect condition that they had
been in from the beginning, consisting entirely of single leaves
of paper, in octavo, full of erasions, interlinings, and
alterations of every kind; so that, in many places, it was not
very certain which of several notes was to be chosen.'
[768] 'On the other hand, were the heat which at present cherishes and
enlivens this globe, allowed to increase beyond the bounds at
present prescribed to it; beside the destruction of all animal and
vegetable life, which would be the immediate and inevitable
consequence, the water would lose its present form, and assume
that of an elastic vapour like air; the solid parts of the globe
would be melted and confounded together, or mixed with the air and
water in smoke and vapour; and nature would return to the original
chaos.' _Black's Lectures_, vol. i. pp. 246, 247.
These, like many other of the speculations of this great thinker, will
find small favour with those purely inductive philosophers, who not only
suppose, perhaps rightly, that all our knowledge is in its beginning
built upon facts, but who countenance, what seems to me, the very
dangerous opinion, that every increase of knowledge must be preceded by
an increase of facts. To such men it will appear, that Black had far
better have occupied himself in making new observations, or devising new
experiments, than in thus indulging his imagination in wild and
unprofitable dreams. They will think, that these flights of fancy are
suitable, indeed, to the poet, but unworthy of that severe accuracy, and
of that close attention to facts, which ought to characterize a
philosopher. In England, especially, there is, among physical inquirers,
an avowed determination to separate philosophy from poetry, and to look
upon them, not only as different, but as hostile. Among that class of
thinkers, whose zeal and ability are beyond all praise, and to whom we
owe almost unbounded obligations, there does undoubtedly exist a very
strong opinion, that, in their own pursuit, the imagination is extremely
dangerous, as leading to speculations, of which the basis is not yet
assured, and generating a desire to catch too eagerly at distant glimpses
before the intermediate ground has been traversed. That the imagination
has this tendency is undeniable. But they who object to it on this
account, and who would, therefore, divorce poetry from philosophy, have,
I apprehend, taken a too limited view of the functions of the human mind,
and of the manner in which truth is obtained. There is, in poetry, a
divine and prophetic power, and an insight into the turn and aspect of
things, which, if properly used, would make it the ally of science
instead of the enemy. By the poet, nature is contemplated on the side of
the emotions; by the man of science, on the side of the understanding.
But the emotions are as much a part of us as the understanding: they are
as truthful; they are as likely to be right. Though their view is
different, it is not capricious. They obey fixed laws; they follow an
orderly and uniform course; they run in sequences; they have their logic
and method of inference. Poetry, therefore, is a part of philosophy,
simply because the emotions are a part of the mind. If the man of science
despises their teaching, so much the worse for him. He has only half his
weapons; his arsenal is unfilled. Conquests, indeed, he may make, because
his native strength may compensate the defects of his equipment. But his
success would be more complete and more rapid, if he were properly
furnished and made ready for the battle. And I cannot but regard as the
worst intellectual symptom of this great country, what I must venture to
call the imperfect education of physical philosophers, as exhibited both
in their writings and in their trains of thought. This is the more
serious, because they, as a body, form the most important class in
England, whether we look at their ability, or at the benefits we have
received from them, or at the influence they are exercising, and are
likely to exercise, over the progress of society. It cannot, however, be
concealed, that they display an inordinate respect for experiments, an
undue love of minute detail, and a disposition to overrate the inventors
of new instruments, and the discoverers of new, but often insignificant,
facts. Their predecessors of the seventeenth century, by using hypotheses
more boldly, and by indulging their imagination more frequently, did
certainly effect greater things, in comparison with the then state of
knowledge, than our contemporaries, with much superior resources, have
been able to achieve. The magnificent generalizations of Newton and
Harvey could never have been completed in an age absorbed in one
unvarying round of experiments and observations. We are in that
predicament, that our facts have outstripped our knowledge, and are now
encumbering its march. The publications of our scientific institutions,
and of our scientific authors, overflow with minute and countless
details, which perplex the judgment, and which no memory can retain. In
vain do we demand that they should be generalized, and reduced into
order. Instead of that, the heap continues to swell. We want ideas, and
we get more facts. We hear constantly of what nature is doing, but we
rarely hear of what man is thinking. Owing to the indefatigable industry
of this and the preceding century, we are in possession of a huge and
incoherent mass of observations, which have been stored up with great
care, but which, until they are connected by some presiding idea, will be
utterly useless. The most effective way of turning them to account, would
be to give more scope to the imagination, and incorporate the spirit of
poetry with the spirit of science. By this means, our philosophers would
double their resources, instead of working, as now, maimed, and with only
half their nature. They fear the imagination, on account of its tendency
to form hasty theories. But, surely, all our faculties are needed in the
pursuit of truth, and we cannot be justified in discrediting any part of
the human mind. And I can hardly doubt, that one of the reasons why we,
in England, made such wonderful discoveries during the seventeenth
century, was because that century was also the great age of English
poetry. The two mightiest intellects our country has produced are
Shakspeare and Newton; and that Shakspeare should have preceded Newton,
was, I believe, no casual or unmeaning event. Shakspeare and the poets
sowed the seed, which Newton and the philosophers reaped. Discarding the
old scholastic and theological pursuits, they drew attention to nature,
and thus became the real founders of all natural science. They did even
more than this. They first impregnated the mind of England with bold and
lofty conceptions. They taught the men of their generation to crave after
the unseen. They taught them to pine for the ideal, and to rise above the
visible world of sense. In this way, by cultivating the emotions, they
opened one of the paths which lead to truth. The impetus which they
communicated, survived their own day, and, like all great movements, was
felt in every department of thought. But now it is gone; and, unless I am
greatly mistaken, physical science is at present suffering from its
absence. Since the seventeenth century, we have had no poet of the
highest order, though Shelley, had he lived, would perhaps have become
one. He had something of that burning passion, that sacred fire, which
kindles the soul, as though it came fresh from the altar of the gods. But
he was cut off in his early prime, when his splendid genius was still in
its dawn. If we except his immature, though marvellous, efforts, we may
assuredly say, that, for nearly two hundred years, England has produced
no poetry which bears those unmistakable marks of inspiration which we
find in Spenser, in Shakspeare, and in Milton. The result is, that we,
separated by so long an interval from those great feeders of the
imagination, who nurtured our ancestors, and being unable to enter fully
into the feelings of poets, who wrote when nearly all opinions, and,
therefore, nearly all forms of emotion, were very different to what they
now are, cannot possibly sympathize with those immortal productions so
closely as their contemporaries did. The noble English poetry of the
sixteenth and seventeenth centuries is read more than ever, but it does
not colour our thoughts; it does not shape our understandings, as it
shaped the understandings of our forefathers. Between us and them is a
chasm, which we cannot entirely bridge. We are so far removed from the
associations amid which those poems were composed, that they do not flash
upon us with that reality and distinctness of aim, which they would have
done, had we lived when they were written. Their garb is strange, and
belongs to another time. Not merely their dialect and their dress, but
their very complexion and their inmost sentiments, tell of bygone days,
of which we have no firm hold. There is, no doubt, a certain ornamental
culture, which the most highly educated persons receive from the
literature of the past, and by which they sometimes refine their taste,
and sometimes enlarge their ideas. But the real culture of a great
people, that which supplies each generation with its principal strength,
consists of what is learnt from the generation immediately preceding.
Though we are often unconscious of the process, we build nearly all our
conceptions on the basis recognized by those who went just before us. Our
closest contact is, not with our forefathers, but with our fathers. To
them we are linked by a genuine affinity, which, being spontaneous, costs
us no effort, and from which, indeed, we cannot escape. We inherit their
notions, and modify them, just as they modified the notions of their
predecessors. At each successive modification, something is lost and
something is gained, until, at length, the original type almost
disappears. Therefore it is, that ideas entertained several generations
ago, bear about the same relation to us, as ideas preserved in a foreign
literature. In both cases, the ideas may adorn our knowledge, but they
are never so thoroughly incorporated with our minds, as to be the
knowledge itself. The assimilation is incomplete, because the sympathy is
incomplete. We have now no great poets; and our poverty in this respect
is not compensated by the fact, that we once had them, and that we may,
and do, read their works. The movement has gone by; the charm is broken;
the bond of union, though not cancelled, is seriously weakened. Hence,
our age, great as it is, and, in nearly all respects, greater than any
the world has yet seen, has, notwithstanding its large and generous
sentiments, its unexampled toleration, its love of liberty, and its
profuse, and almost reckless, charity, a certain material, unimaginative,
and unheroic character, which has made several observers tremble for the
future. So far as I can understand our present condition, I do not
participate in these fears, because I believe that the good we have
already gained, is beyond all comparison greater than what we have lost.
But that something has been lost, is unquestionable. We have lost much of
that imagination, which, though, in practical life, it often misleads,
is, in speculative life, one of the highest of all qualities, being
suggestive as well as creative. Even practically, we should cherish it,
because the commerce of the affections mainly depends on it. It is,
however, declining; while, at the same time, the increasing refinement of
society accustoms us more and more to suppress our emotions, lest they
should be disagreeable to others. And as the play of the emotions is the
chief study of the poet, we see, in this circumstance, another reason
which makes it difficult to rival that great body of poetry which our
ancestors possessed. Therefore, it is doubly incumbent on physical
philosophers to cultivate the imagination. It is a duty they owe to their
own pursuits, which would be enriched and invigorated by such an
enlargement of their resources. It is also a duty which they owe to
society in general; since they, whose intellectual influence is already
greater than that of any other class, and whose authority is perceptibly
on the increase, might have power enough to correct the most serious
deficiency of the present age, and to make us some amends for our
inability to produce such a splendid imaginative literature as that which
our forefathers created, and in which the choicest spirits of the
seventeenth century did, if I may so say, dwell and have their being.
If, therefore, Black had done nothing more than set the example of a
great physical philosopher giving free scope to the imagination, he would
have conferred upon us a boon, the magnitude of which it is not easy to
overrate. And it is very remarkable, that, before he died, that
department of inorganic physics, which he cultivated with such success,
was taken up by another eminent Scotchman, who pursued exactly the same
plan, though with somewhat inferior genius. I allude, of course, to
Leslie, whose researches on heat are well known to those who are occupied
with this subject; while, for our present purpose, they are chiefly
interesting as illustrating that peculiar method which, in the eighteenth
century, seemed essential to the Scotch mind.
About thirty years after Black propounded his famous theory of heat,
Leslie began to investigate the same topic, and, in 1804, published a
special dissertation upon it.[769] In that work, and in some papers in
his _Treatises on Philosophy_, are contained his views, several of which
are now known to be inaccurate,[770] though some are of sufficient value
to mark an epoch in the history of science. Such was his generalization
respecting the connexion between the radiation of heat, and its
reflection; bodies which reflect it most, radiating it least, and those
which radiate it most, reflecting it least. Such, too, was another wide
conclusion, which the best inquirers have since confirmed, namely, that,
while heat is radiating from a body, the intensity of each ray is as the
sine of the angle which it makes with the surface of that body.
[769] Mr. Napier, in his _Memoirs of Leslie_, pp. 16, 17 (prefixed to
_Leslie's Treatises on Philosophy_, Edinb. 1838), says, that he
'composed the bulk of his celebrated work on Heat in the years
1801 and 1802;' but that, in 1793, he propounded 'some of its
theoretical opinions, as well as the germs of its discoveries.' It
appears, however, from his own statement, that he was making
experiments on heat, at all events, as early as 1791. See
_Leslie's Experimental Inquiry into the Nature and Propagation of
Heat_, London, 1804, p. 409.
[770] For specimens of some of his most indefensible speculations, see
_Leslie's Treatises on Philosophy_, pp. 38, 43.
These were important steps, and they were the result of experiments,
preceded by large and judicious hypotheses. In relation, however, to the
economy of nature, considered as a whole, they are of small account in
comparison with what Leslie effected towards consolidating the great idea
of light and heat being identical, and thus preparing his contemporaries
for that theory of the interchange of forces, which is the capital
intellectual achievement of the nineteenth century. But it is interesting
to observe, that, with all his ardour, he could not go beyond a certain
length. He was so hampered by the material tendencies of his time, that
he could not bring himself to conceive heat as a purely supersensual
force, of which temperature was the external manifestation.[771] For
this, the age was barely ripe. We accordingly find him asserting, that
heat is an elastic fluid, extremely subtle, but still a fluid.[772] His
real merit was, that, notwithstanding the difficulties which beset his
path, he firmly seized the great truth, that there is no fundamental
difference between light and heat. As he puts it, each is merely a
metamorphosis of the other. Heat is light in complete repose. Light is
heat in rapid motion. Directly light is combined with a body, it becomes
heat; but when it is thrown off from that body, it again becomes
light.[773]
[771] Though he clearly distinguishes between the two. 'It is almost
superfluous to remark, that the term heat is of ambiguous import,
denoting either a certain sensation, or the external cause which
excites it.' _Leslie on Heat_, p. 137.
[772] 'Heat is an elastic fluid extremely subtle and active.' _Leslie on
Heat_, p. 150. At p. 31, 'calorific and frigorific fluid.' See
also pp. 143, 144; and the attempt to measure its elasticity, in
pp. 177, 178.
[773] 'Heat is only light in the state of combination.' _Leslie on
Heat_, p. 162. 'Heat in the state of emission constitutes light.'
p. 174. 'It is, therefore, the same subtle matter, that, according
to its different modes of existence, constitutes either heat or
light. Projected with rapid celerity, it forms light; in the state
of combination with bodies it acts as heat.' p. 188. See also p.
403, 'different states of the same identical substance.'
Whether this is true or false, we cannot tell; and many years, perhaps
many generations, will have to elapse before we shall be able to tell.
But the service rendered by Leslie is quite independent of the accuracy
of his opinion, as to the manner in which light and heat are
interchanged. That they are interchanged, is the essential and paramount
idea. And we must remember, that he made this idea the basis of his
researches, at a period when some very important facts, or, I should
rather say, some very conspicuous facts, were opposed to it; while the
main facts which favoured it were still unknown. When he composed his
work, the analogies between light and heat, with which we are now
acquainted, had not been discovered; no one being aware, that double
refraction, polarization, and other curious properties, are common to
both. To grasp so wide a truth in the face of such obstacles, was a rare
stroke of sagacity. But, on account of the obstacles, the inductive mind
of England refused to receive the truth, as it was not generalized from a
survey of all the facts. And Leslie, unfortunately for himself, died too
soon to enjoy the exquisite pleasure of witnessing the empirical
corroboration of his doctrine by direct experiment, although he clearly
perceived that the march of discovery, in reference to polarization, was
leading the scientific world to a point, of which his keen eye had
discerned the nature, when, to others, it was an almost invisible speck,
dim in the distant offing.[774]
[774] In 1814, that is ten years after his great work was published, and
about twenty years after it was begun, he writes from Paris: 'My
book on heat is better known' here 'than in England. I was even
reminded of some passages in it which in England were considered
as fanciful, but which the recent discoveries on the polarity of
light have confirmed.' _Napier's Memoirs of Leslie_, p. 28,
prefixed to _Leslie's Philosophical Treatises_, edit. Edinb. 1838.
Leslie died in 1832 (p. 40); and the decisive experiments of
Forbes and Melloni were made between 1834 and 1836.
In regard to the method adopted by Leslie, he assures us, that, in
assuming the principles from which he reasoned, he derived great aid from
poetry; for he knew that the poets are, after their own manner,
consummate observers, and that their united observations form a treasury
of truths, which are nowise inferior to the truths of science, and of
which science must either avail herself, or else suffer from neglecting
them.[775] To apply these truths rightly, and to fit them to the
exigencies of physical inquiry, is, no doubt, a most difficult task,
since it involves nothing less than holding the balance between the
conflicting claims of the emotions and the understanding. Like all great
enterprises, it is full of danger, and, if undertaken by an ordinary
mind, would certainly fail. But there are two circumstances which make it
less dangerous in our time, than in any earlier period. The first
circumstance is, that the supremacy of the human understanding, and its
right to judge all theories for itself, is now more generally admitted
than ever; so that there can be little fear of our leaning to the
opposite side, and allowing poetry to encroach on science. The other
circumstance is, that our knowledge of the laws of nature is much greater
than that possessed by any previous age; and there is, consequently, less
risk of the imagination leading us into error, inasmuch as we have a
large number of well-ascertained truths, which we can confront with every
speculation, no matter how plausible or ingenious it may appear.
[775] 'The easiest mode of conceiving the subject, is to consider the
heat that permeates all bodies, and unites with them in various
proportions, as merely the subtle fluid of light in a state of
combination. When forcibly discharged, or suddenly elicited from
any substance, it again resumes its radiant splendour.' ... 'The
same notion was embraced by the poets, and gives sublimity to
their finest odes.' ... 'Those poetical images which have
descended to our own times, were hence founded on a close
observation of nature. Modern philosophy need not disdain to adopt
them, and has only to expand and reduce to precision the original
conceptions.' _Leslie's Treatises on Philosophy_, pp. 308, 309.
Again, at p. 416: 'This is not the first occasion in which we have
to admire, through the veil of poetical imagery, the sagacity and
penetration of those early sages. It would be weakness to expect
nice conclusions in the infancy of science; but it is arrogant
presumption to regard all the efforts of unaided genius with
disdain.'
On both these grounds, Leslie was, I apprehend, justified in taking the
course which he did. At all events, it is certain, that, by following it,
he came nearer than would otherwise have been possible, to the
conceptions of the most advanced scientific thinkers of our day. He
distinctly recognized that, in the material world, there is neither break
nor pause; so that what we call the divisions of nature have no
existence, except in our minds.[776] He was even almost prepared to do
away with that imaginary difference between the organic and inorganic
world, which still troubles many of our physicists, and prevents them
from comprehending the unity and uninterrupted march of affairs. They,
with their old notions of inanimate matter, are unable to see that all
matter is living, and that what we term death is a mere expression by
which we signify a fresh form of life. Towards this conclusion, all our
knowledge is now converging; and it is certainly no small merit in
Leslie, that he, sixty years ago, when really comprehensive views,
embracing the whole creation, were scarcely known among scientific men,
should have strongly insisted that all forces are of the same kind, and
that we have no right to distinguish between them, as if some were
living, and others were dead.[777]
[776] 'We should recollect that, in all her productions, Nature exhibits
a chain of perpetual gradation, and that the systematic divisions
and limitations are entirely artificial, and designed merely to
assist the memory and facilitate our conceptions.' _Leslie on
Heat_, p. 506.
[777] 'All forces are radically of the same kind, and the distinction of
them into _living_ and _dead_ is not grounded on just principles.'
_Leslie on Heat_, p. 133. Compare p. 299: 'We shall perhaps find,
that this prejudice, like many others, has some semblance of
truth; and that even dead or inorganic substances must, in their
recondite arrangements, exert such varying energies, and _so like
sensation itself_, as if fully unveiled to our eyes, could not
fail to strike us with wonder and surprise.'
We owe much to him, by whom such views were advocated. But they were
then, and in a certain, though far smaller degree, they are now, so out
of the domain of physical experience, that Leslie never could have
obtained them by generalizing in the way which the inductive philosophy
enjoins. His great work on heat was executed, as well as conceived, on
the opposite plan;[778] and his prejudices on this point were so strong,
that we are assured by his biographer, that he would allow no merit to
Bacon, who organized the inductive method into a system, and to whose
authority we in England pay a willing, and I had almost said a servile,
homage.[779]
[778] Mr. Napier, in his _Life of Leslie_, p. 17, says of it, very
gravely, 'Its hypotheses are not warranted by the sober maxims of
inductive logic.'
[779] 'Notwithstanding the contrary testimony, explicitly recorded by
the founders of the English experimental school, he denied all
merit and influence to the immortal delineator of the inductive
logic.' _Napier's Life of Leslie_, p. 42.