[1] A System of Logic, Ratiocinative and Inductive;
being a connected view of the Principles of Evidence,
and the Methods of Scientific Investigation. By John
Stuart Mill. In two volumes. London: Parker.
These are _not_ degenerate days. We have still strong thinkers amongst
us; men of untiring perseverance, who flinch before no difficulties,
who never hide the knot which their readers are only too willing that
they should let alone; men who dare write what the ninety-nine out of
every hundred will pronounce a _dry_ book; who pledge themselves, not
to the public, but to their subject, and will not desert it till their
task is completed. One of this order is Mr John Stuart Mill. The work
he has now presented to the public, we deem to be, after its kind, of
the very highest character, every where displaying powers of clear,
patient, indefatigable thinking. Abstract enough it must be allowed to
be, calling for an unremitted attention, and yielding but little, even
in the shape of illustration, of lighter and more amusing matter; he
has taken no pains to bestow upon it any other interest than what
searching thought and lucid views, aptly expressed, ought of
themselves to create. His subject, indeed--the laws by which human
belief and the inquisition of truth are to be governed and
directed--is both of that extensive and fundamental character, that it
would be treated with success only by one who knew how to resist the
temptations to digress, as well as how to apply himself with vigour to
the solution of the various questions that must rise before him.
"This book," the author says in his preface, "makes no
pretence of giving to the world a new theory of our
intellectual operations. Its claim to attention, if it
possess any, is grounded on the fact, that it is an
attempt not to supersede, but to embody and systematize,
the best ideas which have been either promulgated on its
subject by speculative writers, or conformed to by
accurate thinkers in their scientific enquiries.
"To cement together the detached fragments of a subject,
never yet treated as a whole; to harmonize the true
portions of discordant theories, by supplying the links
of thought necessary to connect them, and by
disentangling them from the errors with which they are
always more or less interwoven--must necessarily require
a considerable amount of original speculation. To other
originality than this, the present work lays no claim.
In the existing state of the cultivation of the
sciences, there would be a very strong presumption
against any one who should imagine that he had effected
a revolution in the theory of the investigation of
truth, or added any fundamentally new process to the
practice of it. The improvement which remains to be
effected in the methods of philosophizing, [and the
author believes that they have much need of
improvement,] can only consist in performing, more
systematically and accurately, operations with which, at
least in their elementary form, the human intellect, in
some one or other of its employments, is already
familiar."
Such is the manly and modest estimate which the author makes of his
own labours, and the work fully bears out the character here given of
it. No one capable of receiving pleasure from the disentanglement of
intricacies, or the clear exposition of an abstruse subject; no one
seeking assistance in the acquisition of distinct and accurate views
on the various and difficult topics which these volumes embrace--can
fail to read them with satisfaction and with benefit.
To give a full account--to give any account--of a work which traverses
so wide a field of subject, would be here a futile attempt; we should,
after all our efforts, merely produce a laboured and imperfect
synopsis, which would in vain solicit the perusal of our readers. What
we purpose doing, is to take up, in the order in which they occur,
some of the topics on which Mr Mill has thrown a new light, or which
he has at least invested with a novel interest by the view he has
given of them. And as, in this selection of topics, we are not bound
to choose those which are most austere and repulsive, we hope that
such of our readers as are not deterred by the very name of logic,
will follow us with some interest through the several points of view,
and the various extracts we shall present to them.
_The Syllogism._--The logic of _Induction_, as that to which attention
has been least devoted, which has been least reduced to systematic
form, and which lies at the basis of all other modes of reasoning,
constitutes the prominent subject of these volumes. Nevertheless, the
old topic of logic proper, or deductive reasoning, is not omitted, and
the first passage to which we feel bound, on many accounts, to give
our attention, is the disquisition on the syllogism.
Fortunately for us it is not necessary, in order to convey the point
of our author's observations upon this head, to afflict our readers
with any dissertation upon _mode_ or _figure_, or other logical
technicalities. The first form or _figure_ of the syllogism (to which
those who have not utterly forgotten their scholastic discipline will
remember that all others may be reduced) is familiar to every one, and
to this alone we shall have occasion to refer.
"All men are mortal.
A king is a man;
Therefore a king is mortal."
Who has not met--what young lady even, though but in her teens, has
not encountered some such charming triplet as this, which looks so
like verse at a distance, but, like some other compositions,
approximates nothing the more on this account to poetry? Who has not
learnt from such examples what is a _major_, what a _middle term_, and
what the _minor_ or conclusion?
As no one, in the present day, advises the adoption, in our
controversies, of the syllogistic forms of reasoning, it is evident
that the value of the syllogism must consist, not in its practical
use, but in the accurate type which it affords of the process of
reasoning, and in the analysis of that process which a full
understanding of it renders necessary. Such an analysis supplies, it
is said, an excellent discipline to the mind, whilst an occasional
reference to the form of the syllogism, as a type or model of
reasoning, insures a steadiness and pertinency of argument. But is the
syllogism, it has been asked, this veritable type of our reasoning?
Has the analysis which would explain it to be such, been accurately
conducted?
Several of our northern metaphysicians, it is well known--as, for
example, Dr Campbell and Dugald Stewart--have laid rude hands upon the
syllogism. They have pronounced it to be a vain invention. They have
argued that no addition of knowledge, no advancement in the
acquisition of truth, no new conviction, can possibly be obtained
through its means, inasmuch as no syllogism can contain any thing in
the conclusion which was not admitted, at the outset, in the first or
major proposition. The syllogism always, say they, involves a _petitio
principii_. Admit the major, and the business is palpably at an end;
the rest is a mere circle, in which one cannot advance, but may get
giddy by the revolution. According to the exposition of logicians
themselves, we simply obtain by our syllogism, the privilege of saying
that, in the _minor_, of some individual of a class, which we had
said, in the _major_, already of the whole class.
Archbishop Whately, our most distinguished expositor and defender of
the Aristotelian logic, meets these antagonists with the resolute
assertion, that their objection to the syllogism is equally valid
against _all reasoning whatever_. He does not deny, but, on the
contrary, in common with every logician, distinctly states, that
whatever is concluded in the minor, must have been previously admitted
in the major, for in this lies the very force and compulsion of the
argument; but he maintains that the syllogism is the true type of all
our reasoning, and that therefore to all our reasoning, the very same
vice, the very same _petitio principii_, may be imputed. The
syllogism, he contends, (and apparently with complete success,) is but
a statement in full of what takes place mentally even in the most
rapid acts of reasoning. We often suppress the major for the sake of
brevity, but it is understood though not expressed; just as in the
same manner as we sometimes content ourselves with merely implying the
conclusion itself, because it is sufficiently evident without further
words. If any one should so far depart from common sense as to
question the mortality of some great king, we should think it
sufficient to say for all argument--the king is a man!--virtually
implying the whole triplet above mentioned:--
"All men are mortal.
The king is a man;
Therefore the king is mortal."
"In pursuing the supposed investigation, (into the operation of
reasoning,)" says Archbishop Whately, "it will be found that every
conclusion is deduced, in reality, from two other propositions,
(thence called _Premisses_;) for though one of these may be and
commonly is suppressed, it must nevertheless be understood as
admitted, as may easily be made evident by supposing the _denial_ of
the suppressed premiss, which will at once invalidate the argument;
_e.g._ if any one, from perceiving that 'the world exhibits marks of
design,' infers that 'it must have had an intelligent author,' though
he may not be aware in his own mind of the existence of any other
premiss, he will readily understand, if it be _denied_ that 'whatever
exhibits marks of design must have had an intelligent author,' that
the affirmative of that proposition is necessary to the solidity of
the argument. An argument thus stated regularly and at full length, is
called a syllogism; which, therefore, is evidently not a peculiar
_kind of argument_, but only a peculiar _form_ of expression, in which
every argument may be stated."--_Whately's Logic_, p. 27.
"It will be found," he continues, "that all valid arguments whatever
may be easily reduced to such a form as that of the foregoing
syllogisms; and that consequently the principle on which they are
constructed is the UNIVERSAL PRINCIPLE of reasoning. So elliptical,
indeed, is the ordinary mode of expression, even of those who are
considered as prolix writers,--_i.e._ so much is implied and left to
be understood in the course of argument, in comparison of what is
actually stated, (most men being impatient, even to excess, of any
appearance of unnecessary and tedious formality of statement,) that a
single sentence will often be found, though perhaps considered as a
single argument, to contain, compressed into a short compass, a chain
of several distinct arguments. But if each of these be fully
developed, and the whole of what the author intended to imply be
stated expressly, it will be found that all the steps, even of the
longest and most complex train of reasoning, may be reduced into the
above form."--P. 32.
That it is not the office of the syllogism to discover _new_ truths,
our logician fully admits, and takes some pains to establish. This is
the office of "other operations of mind," not unaccompanied, however,
with acts of reasoning. Reasoning, argument, inference, (words which
he uses as synonymous,) have not for their object our advancement in
knowledge, or the acquisition of new truths.
"Much has been said," says Archbishop Whately, in another portion of
his work, "by some writers, of the superiority of the inductive to the
syllogistic methods of seeking truth, as if the two stood opposed to
each other; and of the advantage of substituting the _Organon_ of
Bacon for that of Aristotle, &c. &c., which indicates a total
misconception of the nature of both. There is, however, the more
excuse for the confusion of thought which prevails on this subject,
because eminent logical writers have treated, or at least have
appeared to treat, of induction as a kind of argument distinct from
the syllogism; which, if it were, it certainly might be contrasted
with the syllogism: or rather the whole syllogistic theory would fall
to the ground, since one of the very first principles it establishes,
is that _all_ reasoning, on whatever subject, is one and the same
process, which may be clearly exhibited in the form of syllogisms.
"This inaccuracy seems chiefly to have arisen from a vagueness in the
use of the word induction; which is sometimes employed to designate
the process of _investigation_ and of collecting facts, sometimes the
deducing an inference _from_ those facts. The former of these
processes (_viz._ that of observation and experiment) is undoubtedly
_distinct_ from that which takes place in the syllogism; but then it
is not a process of _argumentation_: the latter again _is_ an
argumentative process; but then it is, like all other arguments,
capable of being syllogistically expressed."--P. 263.
"To prove, then, this point demonstratively, (namely, that it is not
by a process of reasoning that new truths are brought to light,)
becomes on these data perfectly easy; for since all reasoning (in the
sense above defined) may be resolved into syllogisms; and since even
the objectors to logic make it a subject of complaint, that in a
syllogism the premises do virtually assert the conclusion, it follows
at once that no new truth (as above defined) can be elicited by any
process of reasoning.
"It is on this ground, indeed, that the justly celebrated author of
the _Philosophy of Rhetoric_ objects to the syllogism altogether, as
necessarily involving a _petitio principii_; an objection which, of
course, he would not have been disposed to bring forward, had he
perceived that, whether well or ill founded, _it lies against all
arguments whatever_. Had he been aware that the syllogism is no
distinct kind of argument otherwise than in form, but is, in fact,
_any_ argument whatever stated regularly and at full length, he would
have obtained a more correct view of the object of all reasoning;
_which is merely to expand and unfold the assertions wrapt up, as it
were, and implied in those with which we set out_, and to bring a
person to perceive and acknowledge the full force of that which he has
admitted; to contemplate it in various points of view; _to admit in
one shape what he has already admitted in another_, and to give up and
disallow whatever is inconsistent with it."--P. 273.
Now, what the Archbishop here advances appears convincing; his
position looks impregnable. The syllogism is not a peculiar mode of
reasoning, (how could it be?)--if any thing at all, it must be a
general formula for expressing the ordinary act of reasoning--and he
shows that the objections made by those who would impugn it, may be
levelled with equal justice against all ratiocination whatever. But
then this method of defending the syllogism, (to those of us who have
stood beside, in the character of modest enquirers, watching the
encounter of keen wits,) does but aggravate the difficulty. Is it
true, then, that in every act of reasoning, we do but conclude in one
form, what, the moment before, we had stated in another? Are we to
understand that such is the final result of the debate? If so, this
act of reasoning appears very little deserving of that estimation in
which it has been generally held. The great prerogative of intelligent
beings (as it has been deemed,) grants them this only--to "admit in
one shape what they had already admitted in another."
From the dilemma in which we are here placed, the Archbishop by no
means releases, or attempts to release us: he seems (something too
much after the manner and disposition generally attributed to masters
in logic-fence,) to have rested satisfied with foiling his opponents
in their attack upon the exact position he had bound himself to
defend. He saves the syllogism; what becomes, in the controversy, of
poor human reason itself, is not his especial concern--it is as much
their business as his. You do not, more than I, he virtually says to
his opponents, intend to resign all reasoning whatever as a mere
inanity; I prove, for my part, that all reasoning is capable of being
put into a syllogistic form, and that your objection, if valid against
the syllogism, is equally valid against all ratiocination. You must
therefore either withdraw your objection altogether, or advance it at
your peril; the difficulty is of your making, you must solve it as you
can. Gentlemen, you must muzzle your own dog.
In this posture of affairs the author of the present work comes to the
rescue. He shall speak in his own words. But we must premise, that
although we do not intend to stint him in our quotation--though we
wish to give him all the sea-room possible; yet, for a _full_
development of his views, we must refer the reader to his volumes
themselves. There are some disquisitions which precede the part we are
about to quote from, which, in order to do complete justice to the
subject, ought to find a place here, as well as in the author's
work--but it is impossible.
"It is universally allowed, that a syllogism is vicious,
if there be any thing more in the conclusion than was
assumed in the premisses. But this is, in fact, to say,
that nothing ever was, or can be, proved by syllogism,
which was not known, or assumed to be known, before. Is
ratiocination, then, not a process of inference? And is
the syllogism, to which the word reasoning has so often
been represented to be exclusively appropriate, not
really entitled to be called reasoning at all? This
seems an inevitable consequence of the doctrine,
admitted by all writers on the subject, that a syllogism
can prove no more than is involved in the premisses. Yet
the acknowledgment so explicitly made, has not prevented
one set of writers from continuing to represent the
syllogism as the correct analysis of what the mind
actually performs in discovering and proving the larger
half of the truths, whether of science or of daily life,
which we believe; while those who have avoided this
inconsistency, and followed out the general theorem
respecting the logical value of the syllogism to its
legitimate corollary, have been led to impute
uselessness and frivolity to the syllogistic theory
itself, on the ground of the _petitio principii_ which
they allege to be inherent in every syllogism. As I
believe both these opinions to be fundamentally
erroneous, I must request the attention of the reader to
certain considerations, without which any just
appreciation of the true character of the syllogism, and
the functions it performs in philosophy, appears to me
impossible; but which seem to me to have been overlooked
or insufficiently adverted to, both by the defenders of
the syllogistic theory, and by its assailants.
"It must be granted, that in every syllogism, considered
as an argument to prove the conclusion, there is a
_petitio principii_. When we say--
'All men are mortal.
Socrates is a man;
THEREFORE
Socrates is mortal'--
it is unanswerably urged by the adversaries of the
syllogistic theory, that the proposition, Socrates is
mortal, is presupposed in the more general assumption,
All men are mortal; that we cannot be assured of the
mortality of all men, unless we were previously certain
of the mortality of every individual man; that if it be
still doubtful whether Socrates, or any other individual
you choose to name, be mortal or not, the same degree of
uncertainty must hang over the assertion, All men are
mortal; that the general principle, instead of being
given as evidence of the particular case, cannot itself
be taken for true without exception, until every shadow
of doubt which could affect any case comprised with it,
is dispelled by evidence _aliunde_, and then what
remains for the syllogism to prove? that, in short, no
reasoning from generals to particulars can, as such,
prove any thing; since from a general principle you
cannot infer any particulars, but those which the
principle itself assumes as foreknown.
"This doctrine is irrefragable; and if logicians, though
unable to dispute it, have usually exhibited a strong
disposition to explain it away, this was not because
they could discover any flaw in the argument itself, but
because the contrary opinion seemed to rest upon
arguments equally indisputable. In the syllogism last
referred to, for example, or in any of those which we
previously constructed, is it not evident that the
conclusion may, to the person to whom the syllogism is
presented, be actually and _bona fide_ a new truth? Is
it not matter of daily experience that truth previously
undreamt of, facts which have not been, and cannot be,
directly observed, are arrived at by way of general
reasoning? We believe that the Duke of Wellington is
mortal. We do not know this by direct observation, since
he is not yet dead. If we were asked how, this being the
case, we know the Duke to be mortal, we should probably
answer, because all men are so. Here, therefore, we
arrive at the knowledge of a truth not (as yet)
susceptible of observation, by a reasoning which admits
of being exhibited in the following syllogism--
'All men are mortal.
The Duke of Wellington is a man;
THEREFORE
The Duke of Wellington is mortal.'
"And since a large portion of our knowledge is thus
acquired, logicians have persisted in representing the
syllogism as a process of inference or proof; although
none of them has cleared up the difficulty which arises
from the inconsistency between that assertion and the
principle, that if there be any thing in the conclusion
which was not already asserted in the premisses, the
argument is vicious. For it is impossible to attach any
serious scientific value to such a mere salvo, as the
distinction drawn between being involved _by
implication_ in the premisses, and being directly
asserted in them. When Archbishop Whately, for example,
says that the object of reasoning is 'merely to expand
and unfold the assertions wrapt up, as it were, and
implied in those with which we set out, and to bring a
person to perceive and acknowledge the full force of
that which he has admitted,' he does not, I think, meet
the real difficulty requiring to be explained; namely,
how it happens that a science like geometry _can_ be all
'wrapt up' in a few definitions and axioms. Nor does
this defence of the syllogism differ much from what its
assailants urge against it as an accusation, when they
charge it with being of no use except to those who seek
to press the consequence of an admission into which a
man has been entrapped, without having considered and
understood its full force. When you admitted the major
premiss, you asserted the conclusion, 'but,' says
Archbishop Whately, 'you asserted it by implication
merely; this, however, can here only mean that you
asserted it unconsciously--that you did not know you
were asserting it; but if so, the difficulty revives in
this shape. Ought you not to have known? Were you
warranted in asserting the general proposition without
having satisfied yourself of the truth of every thing
which it fairly includes? And if not, what, then, is the
syllogistic art but a contrivance for catching you in a
trap, and holding you fast in it?'
"From this difficulty there appears to be but one issue.
The proposition, that the Duke of Wellington is mortal,
is evidently an inference, it is got at as a conclusion
from something else; but do we, in reality, conclude it
from the proposition--All men are mortal? I answer, No.
"The error committed is, I conceive, that of overlooking
the distinction between the two parts of the process of
philosophizing--the inferring part and the registering
part; and ascribing to the latter the functions of the
former. The mistake is that of referring a man to his
own notes for the _origin_ of his knowledge. If a man is
asked a question, and is at the moment unable to answer
it, he may refresh his memory by turning to a memorandum
which he carries about with him. But if he were asked
how the fact came to his knowledge, he would scarcely
answer, because it was set down in his note-book.
"Assuming that the proposition, The Duke of Wellington
is mortal, is immediately an inference from the
proposition, All men are mortal, whence do we derive our
knowledge of that general truth? No supernatural aid
being supposed, the answer must be, from observation.
Now, all which men can observe are individual cases.
From these all general truths must be drawn, and into
these they may be again resolved; for a general truth is
but an aggregate of particular truths--a comprehensive
expression, by which an indefinite number of individual
facts are affirmed or denied at once. But a general
proposition is not merely a compendious form for
recording and preserving in the memory a number of
particular facts, all of which have been observed.
Generalization is not a process of mere naming, it is
also a process of inference. From instances which we
have observed, we feel warranted in concluding, that
what we found true in those instances holds in all
similar ones--past, present, and future, however
numerous they may be. We, then, by that valuable
contrivance of language, which enables us to speak of
many as if they were one, record all that we have
observed, together with all that we infer from our
observations, in one concise expression; and have thus
only one proposition, instead of an endless number, to
remember or to communicate. The results of many
observations and inferences, and instructions for making
innumerable inferences in unforeseen cases, are
compressed into one short sentence.
"When, therefore, we conclude, from the death of John
and Thomas, and every other person we ever heard of in
whose case the experiment had been fairly tried, that
the Duke of Wellington is mortal like the rest, we may,
indeed, pass through the generalization, All men are
mortal, as an intermediate stage; but it is not in the
latter half of the process--the descent from all men to
the Duke of Wellington--that the _inference_ resides.
The inference is finished when we have asserted that all
men are mortal. What remains to be performed afterwards
is merely deciphering our own notes.
"Archbishop Whately has contended, that syllogizing, or
reasoning from generals to particulars, is not,
agreeably to the vulgar idea, a peculiar mode of
reasoning, but the philosophical analysis of the mode in
which all men reason, and must do so if they reason at
all. With the deference due to so high an authority, I
cannot help thinking that the vulgar notion is, in this
case, the more correct. If, from our experience of John,
Thomas, &c. who once were living, but are now dead, we
are entitled to conclude that all human beings are
mortal, we might surely, without any logical
inconsequence, have concluded at once, from those
instances, that the Duke Wellington is mortal. The
mortality of John, Thomas, and Company, is, after all,
the whole evidence we have for the mortality of the Duke
of Wellington. Not one iota is added to the proof by
interpolating a general proposition. Since the
individual cases are all the evidence we can possess;
evidence which no logical form into which we choose to
throw it can make greater than it is; and since that
evidence is either sufficient in itself, or, if
insufficient for one purpose, cannot be sufficient for
the other; I am unable to see why we should be forbidden
to take the shortest cut from these sufficient premisses
to the conclusion, and constrained to travel the 'high
_priori_ road' by the arbitrary fiat of logicians. I
cannot perceive why it should be impossible to journey
from one place to another, unless 'we march up a hill
and then march down again.' It may be the safest road,
and there may be a resting-place at the top of the hill,
affording a commanding view of the surrounding country;
but for the mere purpose of arriving at our journey's
end, our taking that road is perfectly optional: it is a
question of time, trouble, and danger.
"Not only _may_ we reason from particulars to
particulars, without passing through generals, but we
perpetually do so reason. All our earliest inferences
are of this nature. From the first dawn of intelligence
we draw inferences; but years elapse before we learn the
use of general language. The child who, having burnt his
fingers, avoids to thrust them again into the fire, has
reasoned or inferred, though he has never thought of the
general maxim--fire burns. He knows from memory that he
has been burnt, and on this evidence believes, when he
sees a candle, that if he puts his finger into the flame
of it, he will be burnt again. He believes this in every
case which happens to arise; but without looking, in
each instance, beyond the present case. He is not
generalizing; he is inferring a particular from
particulars.--Vol. I. p. 244.
"From the considerations now adduced, the following
conclusions seem to be established:--All inference is
from particulars to particulars: General propositions
are merely registers of such inferences already made,
and short formulae for making more: The major premiss of
a syllogism, consequently, is a formula of this
description; and the conclusion is not an inference
drawn _from_ the formula, but an inference drawn
_according to_ the formula: the real logical antecedent,
or premisses being _the particular facts from which the
general proposition was collected by induction_. * * *
"In the above observations, it has, I think, been
clearly shown, that although there is always a process
of reasoning or inference where a syllogism is used, the
syllogism is not a correct analysis of that process of
reasoning or inference; which is, on the contrary, (when
not a mere inference from testimony,) an inference from
particulars to particulars; authorized by a previous
inference from particulars to generals, and
substantially the same with it: of the nature,
therefore, of Induction. But while these conclusions
appear to me undeniable, I must yet enter a protest, as
strong as that of Archbishop Whately himself, against
the doctrine that the syllogistic art is useless for the
purposes of reasoning. The reasoning lies in the act of
generalisation, not in interpreting the record of that
act; but the syllogistic form is all indispensable
collateral security for the correctness of the
generalisation itself."--P. 259.
By this explanation we are released from the dilemma into which the
syllogistic and non-syllogistic party had together thrown us. We can
acknowledge that the process of reason can be always exhibited in the
form of a syllogism, and yet not be driven to the strange and
perplexing conclusion that our reasoning can never conduct us to a new
truth, never lead us further than to admit in one shape what we had
already admitted in another. We have, or may have, it is true, a
_major_ in all our ratiocination, implied, if not expressed, and are
so far syllogistic; but then the real premiss from which we reason is
the amount of experience on which that major was founded, to which
amount of experience we, in fact, made an addition in our _minor_, or
conclusion.
But while we accept this explanation, and are grateful for the
deliverance it works for us, we must also admit, (and we are not aware
that Mr Mill would controvert this admission,) that there is a large
class of cases in which our reasoning betrays no reference to this
anterior experience, and where the usual explanation given by teachers
of logic is perfectly applicable; cases where our object is, not the
discovery of truth for ourselves, but to convince another of his
error, by showing him that the proposition, which in his blindness or
prejudice he has chosen to contradict, is part and parcel of some
other proposition to which he has given, and is at all times ready to
give, his acquiescence. In such cases, we frequently content ourselves
with throwing before him this alternative--refuse your _major_, to
which you have again and again assented, or accept, as involved in it,
our _minor_ proposition, which you have persisted in controverting.
It will have been gathered from the foregoing train of observation,
that, in direct contradistinction to Archbishop Whately, who had
represented induction (so far as it consisted of an act of
ratiocination) as resolvable into deductive and syllogistic reasoning,
our author has resolved the syllogism, and indeed all deductive
reasoning whatever, ultimately into examples of induction. In doing
this, he is encountered by a metaphysical notion very prevalent in the
present day, which lies across his path, and which he has to remove.
We allude to the distinction between contingent and necessary truths;
it being held by many philosophical writers that all necessary and
universal truths owe their origin, not to experience (except as
_occasion_ of their development,) and not, consequently, to the
ordinary process of induction, but flow from higher sources--flow
immediately from some supreme faculty to which the name of reason has
by some been exclusively appropriated, in order to distinguish it from
the understanding, the faculty judging according to sense. We will
pause a while upon this topic.
_Contingent and Necessary Truths._--Those who have read Mr Whewell's
treatise on the _Philosophy of the Inductive Sciences_, will remember
that there is no topic which that author labours more sedulously to
inculcate than this same distinction between contingent and necessary
truths; and it is against his statement of the doctrine in question,
that Mr Mill directs his observations. Perhaps the controverted tenets
would have sustained a more equal combat under the auspices of a more
practised and more complete metaphysician than Mr Whewell; but a
difficulty was probably experienced in finding a statement in any
other well-known English author full and explicit. Referring ourselves
to Mr Whewell's volumes for an extract, in order to give the
distinction here contended against the advantage of an exposition in
the words of one who upholds it, we are embarrassed by the number
which offer themselves. From many we select the following statement:--
"Experience," says Mr Whewell, "must always consist of a limited
number of observations. And, however numerous these may be, they can
show nothing with regard to the infinite number of cases in which the
experiment has not been made. Experience, being thus unable to prove a
fact to be universal, is, as will readily be seen, still more
incapable of proving a fact to be necessary. Experience cannot,
indeed, offer the smallest ground for the necessity of a proposition.
She can observe and record what has happened; but she cannot find, in
any case, or in any accumulation of cases, any reason for what _must_
happen. She may see objects side by side, but she cannot see a reason
why they must be ever side by side. She finds certain events to occur
in succession; but the succession supplies, in its occurrence, no
reason for its recurrence. She contemplates external objects; but she
cannot detect any internal bond which indissolubly connects the future
with the past, the possible with the real. To learn a proposition by
experience, and to see it to be necessarily true, are two altogether
different processes of thought.
"But it may be said, that we do learn, by means of observation and
experience, many universal truths; indeed, all the general truths of
which science consists. Is not the doctrine of universal gravitation
learned by experience? Are not the laws of motion, the properties of
light, the general properties of chemistry, so learned? How, with
these examples before us, can we say that experience teaches no
universal truths?
"To this we reply, that these truths can only be known to be
_general_, not universal, if they depend upon experience alone.
Experience cannot bestow that universality which she herself cannot
have, and that necessity of which she has no comprehension. If these
doctrines are universally true, this universality flows from the
_ideas_ which we apply to our experience, and which are, as we have
seen, the real sources of necessary truth. How far these ideas can
communicate their universality and necessity to the results of
experience, it will hereafter be our business to consider. It will
then appear, that when the mind collects from observation truths of a
wide and comprehensive kind, which approach to the simplicity and
universality of the truths of pure science; she gives them this
character by throwing upon them the light of her own fundamental
ideas."--_Whewell_, Vol. I. p. 60.
Accordingly, Mr Whewell no sooner arrives at any truth which admits of
an unconditional positive statement--a statement defying all rational
contradiction--than he abstracts it from amongst the acquisitions of
experience, and throwing over it, we suppose, the light of these
fundamental ideas, pronounces it enrolled in the higher class of
universal and necessary truths. The first laws of motion, though
established through great difficulties against the most obstinate
preconceptions, and by the aid of repeated experiments, are, when
surveyed in their present perfect form, proclaimed to be, not
acquisitions of experience, but truths emanating from a higher and
more mysterious origin.[2]
[2] Necessary truths multiply on us very fast. "We
maintain," says Mr Whewell, "that this equality of
_mechanical action and reaction_ is one of the
principles which do not flow from, but regulate, our
experience. A mechanical pressure, not accompanied by an
equal and opposite pressure, can no more be given by
experience than two unequal right angles. With the
supposition of such inequalities, space ceases to be
space, form ceases to be form, matter ceases to be
matter." And again he says, "_That the parallelogram of
forces is a necessary truth_;" a law of motion of which
we surely can _conceive_ its opposite to be true. In
some of these instances Mr Whewell appears, by a
confusion of thought, to have given to the _physical
fact_ the character of necessity which resides in the
mathematical formula employed for its expression.
Whether a moving body would communicate motion to
another body--whether it would lose its own motion by so
doing--or what would be the result if a body were struck
by two other bodies moving in different directions--are
questions which, if they could be asked us prior to
experience, we could give no answer whatever to--which
we can easily conceive to admit of a quite different
answer to that which experience has taught us to give.
This distinction, which assigns a different mental origin to truths,
simply because (from the nature of the subject-matter, as it seems to
us) there is a difference with regard to the sort of certainty we feel
of them, has always appeared to us most unphilosophical. It is
admitted that we arrive at a general proposition through experience;
there is no room, therefore, for quibbling as to the meaning of the
term experience--it is understood that when we speak of a truth being
derived from experience, we imply the usual exercise of our mental
faculties; it is the step from a general to a universal proposition
which alone occasions this perplexing distinction. The dogma is
this--that experience can only teach us by a limited number of
examples, and therefore can never establish a universal proposition.
But if _all_ experience is in favour of a proposition--if no
experience has occurred even to enable the imagination to conceive its
opposite, what more can be required to convert the general into a
universal proposition?
Strange to say, the attribution of these characteristics of
universality and necessity, becomes, amongst those who loudly insist
upon the palpable nature of the distinction we are now examining, a
matter of controversy; and there are a class of scientific truths, of
which it is debated whether they are contingent or necessary. The
only test that they belong to the latter order is, the impossibility
of conceiving their opposites to be the truth; and it seems that men
find a great difference in their powers of conception, and that what
is impossible with one is possible with another. But (wisely, too)
passing this over, and admitting that there is a distinction (though
a very ill-defined one) between the several truths we entertain of
this nature; namely, that some we find it impossible, even in
imagination, to contradict, whilst of others we can suppose it
possible that they should cease to be truths--does it follow that
different faculties of the mind are engaged in the acquisition of
them? Does nothing depend on the nature of the subject itself? "That
two sides of a triangle," says Mr Whewell, "are greater than the
third, is a universal and necessary geometrical truth; it is true of
all triangles; it is true in such a way that the contrary cannot be
conceived. _Experience could not prove such a proposition._"
Experience is allowed to prove it of this or that triangle, but not
as an inseparable property of a triangle. We are at a loss to
perceive why the same faculties of the mind that can judge, say of
the properties of animal life, of organized beings, cannot judge of
the properties of a figure--properties which must immediately be
conceived to exist the moment the figure is presented to the
imagination. We say, for instance, of any animal, not because it is
this or that animal, a sheep or an ox, but simply _as_ animal, that
it must sustain itself by food, by the process of assimilation. This,
however, is merely a contingent truth, because it is in our power to
conceive of organized beings whose substance shall not wear away, and
consequently shall not need perpetual restoration. But what faculty
of the mind is unemployed here that is engaged in perceiving the
property of a triangle, that _as_ triangle, it must have two sides
greater than the third? The truths elicited in the two cases have a
difference, inasmuch as a triangle differs from an animal in this,
that it is impossible to conceive other triangles than those to which
your truth is applicable, and therefore the proposition relating to
the triangle is called a necessary truth. But surely this difference
lies in the subject-matter, not in the nature of our mental
faculties.
But we had not intended to interpose our own lucubrations in the place
of those of Mr Mill.
"Although Mr Whewell," says our author, "has naturally
and properly employed a variety of phrases to bring his
meaning more forcibly home, he will, I presume, allow
that they are all equivalent; and that what he means by
a necessary truth, would be sufficiently defined, a
proposition the negation of which is not only false, but
inconceivable. I am unable to find in any of Mr
Whewell's expressions, turn them what way you will, a
meaning beyond this, and I do not believe he would
contend that they mean any thing more.
"This, therefore, is the principle asserted: that
propositions, the negation of which is inconceivable, or
in other words, which we cannot figure to ourselves as
being false, must rest upon evidence of higher and more
cogent description than any which experience can afford.
And we have next to consider whether there is any ground
for this assertion.
"Now, I cannot but wonder that so much stress should be
laid upon the circumstance of inconceivableness, when
there is such ample experience to show that our capacity
or incapacity for conceiving a thing has very little to
do with the possibility of the thing in itself; but is
in truth very much an affair of accident, and depends
upon the past habits and history of our own minds. There
is no more generally acknowledged fact in human nature,
than the extreme difficulty at first felt in conceiving
any thing as possible, which is in contradiction to
long-established and familiar experience, or even to old
and familiar habits of thought. And this difficulty is a
necessary result of the fundamental laws of the human
mind. When we have often seen and thought of two things
together, and have never, in any one instance, either
seen or thought of them separately, there is by the
primary law of association an increasing difficulty,
which in the end becomes insuperable, of conceiving the
two things apart. This is most of all conspicuous in
uneducated persons, who are, in general, utterly unable
to separate any two ideas which have once become firmly
associated in their minds, and, if persons of cultivated
intellect have any advantage on the point, it is only
because, having seen and heard and read more, and being
more accustomed to exercise their imagination, they
have experienced their sensations and thoughts in more
varied combinations, and have been prevented from
forming many of these inseparable associations. But this
advantage has necessarily its limits. The man of the
most practised intellect is not exempt from the
universal laws of our conceptive faculty. If daily habit
presents to him for a long period two facts in
combination, and if he is not led, during that period,
either by accident or intention, to think of them apart,
he will in time become incapable of doing so, even by
the strongest effort; and the supposition, that the two
facts can be separated in nature, will at last present
itself to his mind with all the characters of an
inconceivable phenomenon. There are remarkable instances
of this in the history of science; instances in which
the wisest men rejected as impossible, because
inconceivable, things which their posterity, by earlier
practice, and longer perseverance in the attempt, found
it quite easy to conceive, and which every body now
knows to be true. There was a time when men of the most
cultivated intellects, and the most emancipated from the
dominion of early prejudice, could not credit the
existence of antipodes; were unable to conceive, in
opposition to old association, the force of gravity
acting upwards instead of downwards. The Cartesians long
rejected the Newtonian doctrine of the gravitation of
all bodies towards one another, on the faith of a
general proposition, the reverse of which seemed to them
to be inconceivable--the proposition, that a body cannot
act where it is not. All the cumbrous machinery of
imaginary vortices, assumed without the smallest
particle of evidence, appeared to these philosophers a
more rational mode of explaining the heavenly motions,
than one which involved what appeared to them so great
an absurdity. And they, no doubt, found it as impossible
to conceive that a body should act upon the earth at the
distance of the sun or moon, as we find it to conceive
an end to space or time, or two straight lines inclosing
a space. Newton himself had not been able to realize the
conception, or we should not have had his hypothesis of
a subtle ether, the occult cause of gravitation; and his
writings prove, that although he deemed the particular
nature of the intermediate agency a matter of
conjecture, the necessity of _some_ such agency appeared
to him indubitable. It would seem that, even now, the
majority of scientific men have not completely got over
this very difficulty; for though they have at last
learned to conceive the sun _attracting_ the earth
without any intervening fluid, they cannot yet conceive
the sun _illuminating_ the earth without some such
medium.
"If, then, it be so natural to the human mind, even in
its highest state of culture, to be incapable of
conceiving, and on that ground to believe impossible,
what is afterwards not only found to be conceivable, but
proved to be true; what wonder if, in cases where the
association is still older, more confirmed, and more
familiar, and in which nothing even occurs to shake our
conviction, or even to suggest to us any conception at
variance with the association, the acquired incapacity
should continue, and be mistaken for a natural
incapacity? It is true our experience of the varieties
in nature enables us, within certain limits, to conceive
other varieties analogous to them. We can conceive the
sun or moon falling, for although we never saw them
fall, nor ever perhaps imagined them falling, we have
seen so many other things fall, that we have innumerable
familiar analogies to assist the conception; which,
after all, we should probably have some difficulty in
framing, were we not well accustomed to see the sun and
moon move, (or appear to move,) so that we are only
called upon to conceive a slight change in the direction
of motion, a circumstance familiar to our experience.
But when experience affords no model on which to shape
the new conception, how is it possible for us to form
it? How, for example, can we imagine an end to space and
time? We never saw any object without something beyond
it, nor experienced any feeling without something
following it. When, therefore, we attempt to conceive
the last point of space, we have the idea irresistibly
raised of other points beyond it. When we try to imagine
the last instant of time, we cannot help conceiving
another instant after it. Nor is there any necessity to
assume, as is done by the school to which Mr Whewell
belongs, a peculiar fundamental law of the mind to
account for the feeling of infinity inherent in our
conception of space and time; that apparent infinity is
sufficiently accounted for by simple and universally
acknowledged laws."--Vol. I. p. 313.
Mr Mill does not deny that there exists a distinction, as regards
ourselves, between certain truths (namely, that of some, we cannot
conceive them to be other than truths,) but he sets no value on this
distinction, inasmuch as there is no proof that it has its counterpart
in things themselves; the impossibility of a thing being by no means
measured by our inability to conceive it. And we may observe, that Mr
Whewell, in consistency with the metaphysical doctrine upon space and
time which he has borrowed from Kant, ought, under another shape, to
entertain a similar doubt as to whether this distinction represent any
real distinction in the nature of things. He considers, with Kant,
that space is only that _form_ with which the human mind invests
things--that it has no other than this merely mental existence--is
purely subjective. Presuming, therefore, that the mind is, from its
constitution, utterly and for ever unable to conceive the opposite of
certain truths, (those, for instance, of geometry;) yet as the
existence of space itself is but a subjective truth, it must follow
that all other truths relating to it are subjective also. The mind is
not conversant with things in themselves, in the truths even of
geometry; nor is there any positive objective truth in one department
of science more than another. Mr Whewell, therefore, though he
advocates this distinction between necessary and contingent truth with
a zeal which would seem to imply that something momentous, or of
peculiar interest, was connected with it, can advocate it only as a
matter of abstract metaphysical science. He cannot participate in that
feeling of exaltation and mystery which has led many to expatiate upon
a necessary and absolute truth which the Divine Power itself cannot
alter, which is equally irresistible, equally binding and compulsory,
with God as with man. Of this spirit of philosophical enthusiasm Mr
Whewell cannot partake. Space and Time, with all their properties and
phenomena, are but recognized as the modes of thought of a human
intelligence.
We have marked a number of passages for annotation and extract--a far
greater number than we can possibly find place for alluding to. One
subject, however, which lies at the very basis of all our science, and
which has received a proportionate attention from Mr Mill, must not be
amongst those which are passed over. We mean the law of _Causation_.
What should be described as the complete and adequate notion of a
cause, we need not say is one of the moot points of philosophy.
According to one school of metaphysicians, there is in our notion of
cause an element not derived from experience, which, it is confessed
on all hands, can teach us only the _succession_ of events. Cause,
with them, is that invisible power, that mysterious bond, which this
succession does but signify: with other philosophers this succession
constitutes the whole of any intelligible notion we have of cause. The
latter opinion is that of Mr Mill; at the same time the question is
one which lies beyond or beside the scope of his volumes. He is
concerned only with phenomena, not with the knowledge (if such there
be) of "things in themselves;" that part, therefore, of our idea of
cause which, according to all systems of philosophy, is won from
experience, and concerns phenomena alone, is sufficient for his
purpose. That every event has a cause, that is, a previous and
uniformly previous event, and that whatever has happened will, in the
like circumstances, happen again--these are the assumptions necessary
to science, and these no one will dispute.
Mr Mill has made a happy addition to the usual definition of cause
given by that class of metaphysicians to which he himself belongs, and
which obviates a plausible objection urged against it by Dr Reid and
others. These have argued, that if cause be nothing more than
invariable antecedence, then night may be said to be the cause of day,
for the one invariably precedes the other. Day does succeed to night,
but only on certain conditions--namely, that the sun rise. "The
succession," observes Mr Mill, "which is equivalent and synonymous to
cause, must be not only invariable but unconditional. We may define,
therefore," says our author, "the cause of a phenomenon to be the
antecedent, or the concurrence of antecedents, upon which it is
invariably and _unconditionally_ consequent."--Vol. I. p. 411.
A dilemma may be raised of this kind. The universality of the law of
causation--in other words, the uniform course of nature--is the
fundamental principle on which all induction proceeds, the great
premise on which all our science is founded. But if this law itself be
the result only of experience, itself only a great instance of
induction, so long as nature presents cases requiring investigation,
where the causes are unknown to us, so long the law itself is
imperfectly established. How, then, can this law be a guide and a
premiss in the investigations of science, when those investigations
are necessary to complete the proof of the law itself? How can this
principle accompany and authorise every step we take in science, which
itself needs confirmation so long as a process of induction remains to
be performed? Or how can this law be established by a series of
inductions, in making which it has been taken for granted?
Objections which wear the air of a quibble have often this
advantage--they put our knowledge to the test. The obligation to find
a complete answer clears up our own conceptions. The observations
which Mr Mill makes on this point, we shall quote at length. They are
taken from his chapter on the _Evidence of the Law of Universal
Causation_; the views in which are as much distinguished for boldness
as for precision.
After having said, that in all the several methods of induction the
universality of the law of causation is assumed, he continues:--
"But is this assumption warranted? Doubtless (it may be
said) _most_ phenomena are connected as effects with
some antecedent or cause--that is, are never produced
unless some assignable fact has preceded them; but the
very circumstance, that complicated processes of
induction are sometimes necessary, shows that cases
exist in which this regular order of succession is not
apparent to our first and simplest apprehension. If,
then, the processes which bring these cases within the
same category with the rest, require that we should
assume the universality of the very law which they do
not at first sight appear to exemplify, is not this a
real _petitio principii_? Can we prove a proposition by
an argument which takes it for granted? And, if not so
proved, on what evidence does it rest?
"For this difficulty, which I have purposely stated in
the strongest terms it would admit of, the school of
metaphysicians, who have long predominated in this
country, find a ready salvo. They affirm that the
universality of causation is a truth which we cannot
help believing; that the belief in it is an instinct,
one of the laws of our believing faculty. As the proof
of this they say, and they have nothing else to say,
that every body _does_ believe it; and they number it
among the propositions, rather numerous in their
catalogue, which may be logically argued against, and
perhaps cannot be logically proved, but which are of
higher authority than logic, and which even he who
denies in speculation, shows by his habitual practice
that his arguments make no impression on himself.
"I have no intention of entering into the merits of this
question, as a problem of transcendental metaphysics.
But I must renew my protest against adducing, as
evidence of the truth of a fact in external nature, any
necessity which the human mind may be conceived to be
under of believing it. It is the business of human
intellect to adapt itself to the realities of things,
and not to measure those realities by its own capacities
of comprehension. The same quality which fits mankind
for the offices and purposes of their own little life,
the tendency of their belief to follow their experience,
incapacitates them for judging of what lies beyond. Not
only what man can know, but what he can conceive,
depends upon what he has experienced. Whatever forms a
part of all his experience, forms a part also of all his
conceptions, and appears to him universal and necessary,
though really, for aught he knows, having no existence
beyond certain narrow limits. The habit, however, of
philosophical analysis, of which it is the surest effect
to enable the mind to command, instead of being
commanded by, the laws of the merely passive part of its
own nature, and which, by showing to us that things are
not necessarily connected in fact because their ideas
are connected in our minds, is able to loosen
innumerable associations which reign despotically over
the undisciplined mind; this habit is not without power
even over those associations which the philosophical
school, of which I have been speaking, regard as connate
and instinctive. I am convinced that any one accustomed
to abstraction and analysis, who will fairly exert his
faculties for the purpose, will, when his imagination
has once learned to entertain the notion, find no
difficulty in conceiving that in some one, for instance,
of the many firmaments into which sidereal astronomy now
divides the universe, events may succeed one another at
random, without any fixed law; nor can any thing in our
experience, or in our mental nature, constitute a
sufficient, or indeed any, reason for believing that
this is nowhere the case. The grounds, therefore, which
warrant us in rejecting such a supposition with respect
to any of the phenomena of which we have experience,
must be sought elsewhere than in any supposed necessity
of our intellectual faculties.
"As was observed in a former place, the belief we
entertain in the universality, throughout nature, of the
law of cause and effect, is itself an instance of
induction; and by no means one of the earliest which any
of us, or which mankind in general, can have made. We
arrive at this universal law by generalisation from many
laws of inferior generality. The generalising propensity
which, instinctive or not, is one of the most powerful
principles of our nature, does not indeed wait for the
period when such a generalisation becomes strictly
legitimate. The mere unreasoning propensity to expect
what has been often experienced, doubtless led men to
believe that every thing had a cause, before they could
have conclusive evidence of that truth. But even this
cannot be supposed to have happened until many cases of
causation, or, in other words, many partial uniformities
of sequence, had become familiar. The more obvious of
the particular uniformities suggest and prove the
general uniformity; and that general uniformity, once
established, enables us to prove the remainder of the
particular uniformities of which it is made up. * * *
"With respect to the general law of causation, it does
appear that there must have been a time when the
universal prevalence of that law throughout nature could
not have been affirmed in the same confident and
unqualified manner as at present. There was a time when
many of the phenomena of nature must have appeared
altogether capricious and irregular, not governed by any
laws, nor steadily consequent upon any causes. Such
phenomena, indeed, were commonly, in that early stage of
human knowledge, ascribed to the direct intervention of
the will of some supernatural being, and therefore still
to a cause. This shows the strong tendency of the human
mind to ascribe every phenomenon to some cause or other;
but it shows also that experience had not, at that time,
pointed out any regular order in the occurrence of those
particular phenomena, nor proved them to be, as we now
know that they are, dependent upon prior phenomena as
their proximate causes. There have been sects of
philosophers who have admitted what they termed Chance
as one of the agents in the order of nature by which
certain classes of events were entirely regulated; which
could only mean that those events did not occur in any
fixed order, or depend upon uniform laws of causation.
* * *
"The progress of experience, therefore, has dissipated
the doubt which must have rested upon the universality
of the law of causation, while there were phenomena
which seemed to be _sui generis_; not subject to the
same laws with any other class of phenomena, and not as
yet ascertained to have peculiar laws of their own. This
great generalisation, however, might reasonably have
been, as it in fact was by all great thinkers, acted
upon as a probability of the highest order, before there
were sufficient grounds for receiving it as a certainty.
For, whatever has been found true in innumerable
instances, and never found to be false after due
examination in any, we are safe in acting upon as
universal provisionally, until an undoubted exception
appears; provided the nature of the case be such that a
real exception could scarcely have escaped our notice.
When every phenomenon that we ever knew sufficiently
well to be able to answer the question, had a cause on
which it was invariably consequent, it was more rational
to suppose that our inability to assign the causes of
other phenomena arose from our ignorance, than that
there were phenomena which were uncaused, and which
happened accidentally to be exactly those which we had
hitherto had no sufficient opportunity of
studying."--Vol. II. p. 108.
_Hypotheses._--Mr Mill's observations on the use of hypotheses in
scientific investigation, except that they are characterized by his
peculiar distinctness and accuracy of thought, do not differ from the
views generally entertained by writers on the subject. We are induced
to refer to the topic, to point out what seems to us a harsh measure
dealt out to the undulatory theory of light--harsh when compared with
the reception given to a theory of Laplace, having for its object to
account for the origin of the planetary system.
We had occasion to quote a passage from Mr Mill, in which he remarks
that the majority of scientific men seem not yet to have completely
got over the difficulty of conceiving matter to act (contrary to the
old maxim) where it is not; "for though," he says, "they have at last
learned to conceive the sun _attracting_ the earth without any
intervening fluid, they cannot yet conceive the sun _illuminating_ the
earth without some such medium." But it is not only this difficulty
(which doubtless, however, is felt) of conceiving the sun illuminating
the earth without any medium by which to communicate its influence,
which leads to the construction of the hypothesis, either of an
undulating ether, or of emitted particles. The analogy of the other
senses conducts us almost irresistibly to the imagination of some such
medium. The nerves of sense are, apparently, in all cases that we can
satisfactorily investigate, affected by contact, by impulse. The nerve
of sight itself, we know, when touched or pressed upon, gives out the
sensation of light. These reasons, in the first place, conduct us to
the supposition of some medium, having immediate communication with
the eye; which medium, though we are far from saying that its
existence is established, is rendered probable by the explanation it
affords of optical phenomena. At the same time it is evident that the
hypothesis of an undulating ether, assumes a fluid or some medium, the
existence of which cannot be directly ascertained. Thus stands the
hypothesis of a luminiferous ether--in what must be allowed to be a
very unsatisfactory condition. But a condition, we think, very
superior to the astronomical speculation of Laplace, which Mr Mill,
after scrutinizing the preceding hypothesis with the utmost
strictness, is disposed to treat with singular indulgence.
"The speculation is," we may as well quote throughout Mr
Mill's words, "that the atmosphere of the sun originally
extended to the present limits of the solar system: from
which, by the process of cooling, it has contracted to
its present dimensions; and since, by the general
principles of mechanics, the rotation of the sun and its
accompanying atmosphere must increase as rapidly as its
volume diminishes, the increased centrifugal force
generated by the more rapid rotation, overbalancing the
action of gravitation, would cause the sun to abandon
successive rings of vaporous matter, which are supposed
to have condensed by cooling, and to have become our
planets.
"There is in this theory," Mr Mill proceeds, "no unknown
substance introduced upon supposition, nor any unknown
property or law ascribed to a known substance. The known
laws of matter authorize us to suppose, that a body
which is constantly giving out so large an amount of
heat as the sun is, must be progressively cooling, and
that by the process of cooling it must contract; if,
therefore, we endeavour, from the present state of that
luminary, to infer its state in a time long past, we
must necessarily suppose that its atmosphere extended
much further than at present, and we are entitled to
suppose that it extended as far as we can trace those
effects which it would naturally leave behind it on
retiring; and such the planets are. These suppositions
being made, it follows from known laws that successive
zones of the solar atmosphere would be abandoned; that
these would continue to revolve round the sun with the
same velocity as when they formed part of his substance,
and that they would cool down, long before the sun
himself, to any given temperature, and consequently to
that at which the greater part of the vaporous matter of
which they consisted would become liquid or solid. The
known law of gravitation would then cause them to
agglomerate in masses, which would assume the shape our
planets actually exhibit; would acquire, each round its
own axis, a rotatory movement; and would in that state
revolve, as the planets actually do, about the sun, in
the same direction with the sun's rotation, but with
less velocity, and each of them in the same periodic
time which the sun's rotation occupied when his
atmosphere extended to that point; and this also M.
Comte has, by the necessary calculations, ascertained to
be true, within certain small limits of error. There is
thus in Laplace's theory nothing hypothetical; it is an
example of legitimate reasoning from a present effect to
its past cause, according to the known laws of that
case; it assumes nothing more than that objects which
really exist, obey the laws which are known to be obeyed
by all terrestrial objects resembling them."--Vol. II.
p. 27.
Now, it seems to us that there is quite as much of hypothesis in this
speculation of Laplace as in the undulatory theory of light. This
atmosphere of the sun extending to the utmost limits of our planetary
system! What proof have we that it ever existed? what possible
grounds have we for believing, what motive even for imagining such a
thing, but the very same description of proof given and rejected for
the existence of a luminiferous ether--namely, that it enables us to
explain certain events supposed to result from it? Nor is the thing
here imagined any the less a novelty, because it bears the old name of
an atmosphere. An atmosphere containing in itself all the various
materials which compose our earth, and whatever else may enter into
the composition of the other planets, is as violent a supposition as
an ether, not perceptible to the senses except by its influence on the
nerves of sight. And this cooling down of the sun! What fact in our
experience enables us to advance such a supposition? We might as well
say that the sun was getting hotter every year, or harder or softer,
or larger or smaller. Surely Mr Mill could not have been serious when
he says, that "the known laws of matter authorize us to suppose, that
a body which is constantly _giving out so large an amount of heat_ as
the sun is, must be progressively cooling"--knowing, as we do, as
little how the sun occasions heat as how it produces light. Neither
can it be contended that because no absolutely new substance, or new
property of matter, is introduced, but a fantastic conception is
framed out of known substances and known properties, that therefore
there is less of rash conjecture in the supposition. In fine, it must
be felt by every one who reads the account of this speculation of
Laplace, that the only evidence which produces the least effect upon
his mind, is the corroboration which it receives from the calculations
of the mathematician--a species of proof which Mr Mill himself would
not estimate very highly.
Many are the topics which are made to reflect a new light as Mr Mill
passes along his lengthened course; we might quote as instances, his
chapters on _Analogy_ and the _Calculation of Chances_: and many are
the grave and severe discussions that would await us were we to
proceed to the close of his volumes, especially to that portion of his
work where he applies the canons of science to investigations which
relate to human nature and the characters of men. But enough for the
present. We repeat, in concluding, the same sentiment that we
expressed at the commencement, that such a work as this goes far to
redeem the literature of our age from the charge of frivolity and
superficiality. Those who have been trained in a different school of
thinking, those who have adopted the metaphysics of the transcendental
philosophy, will find much in these volumes to dissent from; but no
man, be his pretensions or his tenets what they may, who has been
accustomed to the study of philosophy, can fail to recognize and
admire in this author that acute, patient, enlarged, and persevering
thought, which gives to him who possesses it the claim and right to
the title of philosopher. There are few men who--applying it to his
own species of excellence--might more safely repeat the _Io sono
anche!_ of the celebrated Florentine.