LANGUAGE--PROPOSITIONS CONCERNING NECESSARY TRUTHS.
Though we may accept Hume's conclusion that speechless animals think,
believe, and reason; yet, it must be borne in mind, that there is an
important difference between the signification of the terms when applied
to them and when applied to those animals which possess language. The
thoughts of the former are trains of mere feelings; those of the latter
are, in addition, trains of the ideas of the signs which represent
feelings, and which are called "words."
A word, in fact, is a spoken or written sign, the idea of which is, by
repetition, so closely associated with the idea of the simple or complex
feeling which it represents, that the association becomes indissoluble.
No Englishman, for example, can think of the word "dog" without
immediately having the idea of the group of impressions to which that
name is given; and conversely, the group of impressions immediately
calls up the idea of the word "dog."
The association of words with impressions and ideas is the process of
naming; and language approaches perfection, in proportion as the shades
of difference between various ideas and impressions are represented by
differences in their names.
The names of simple impressions and ideas, or of groups of co-existent
or successive complex impressions and ideas, considered _per se_, are
substantives; as redness, dog, silver, mouth; while the names of
impressions or ideas considered as parts or attributes of a complex
whole, are adjectives. Thus redness, considered as part of the complex
idea of a rose, becomes the adjective red; flesh-eater, as part of the
idea of a dog, is represented by carnivorous; whiteness, as part of the
idea of silver, is white; and so on.
The linguistic machinery for the expression of belief is called
_predication_; and, as all beliefs express ideas of relation, we may say
that the sign of predication is the verbal symbol of a feeling of
relation. The words which serve to indicate predication are verbs. If I
say "silver" and then "white," I merely utter two names; but if I
interpose between them the verb "is," I express a belief in the
co-existence of the feeling of whiteness with the other feelings which
constitute the totality of the complex idea of silver; in other words, I
predicate "whiteness" of silver.
In such a case as this, the verb expresses predication and nothing else,
and is called a copula. But, in the great majority of verbs, the word is
the sign of a complex idea, and the predication is expressed only by its
form. Thus in "silver shines," the verb "to shine" is the sign for the
feeling of brightness, and the mark of predication lies in the form
"shine-_s_."
Another result is brought about by the forms of verbs. By slight
modifications they are made to indicate that a belief, or predication,
is a memory, or is an expectation. Thus "silver _shone_" expresses a
memory; "silver _will_ shine" an expectation.
The form of words which expresses a predication is a proposition.
Hence, every predication is the verbal equivalent of a belief; and, as
every belief is either an immediate consciousness, a memory, or an
expectation, and as every expectation is traceable to a memory, it
follows that, in the long run, all propositions express either immediate
states of consciousness, or memories. The proposition which predicates A
of X must mean either, that the fact is testified by my present
consciousness, as when I say that two colours, visible at this moment,
resemble one another; or that A is indissolubly associated with X in
memory; or that A is indissolubly associated with X in expectation. But
it has already been shown that expectation is only an expression of
memory.
Hume does not discuss the nature of language, but so much of what
remains to be said, concerning his philosophical tenets, turns upon the
value and the origin of verbal propositions, that this summary sketch of
the relations of language to the thinking process will probably not be
deemed superfluous.
So large an extent of the field of thought is traversed by Hume, in his
discussion of the verbal propositions in which mankind enshrine their
beliefs, that it would be impossible to follow him throughout all the
windings of his long journey, within the limits of this essay. I
purpose, therefore, to limit myself to those propositions which
concern--1. Necessary Truths; 2. The Order of Nature; 3. The Soul; 4.
Theism; 5. The Passions and Volition; 6. The Principle of Morals.
Hume's views respecting necessary truths, and more particularly
concerning causation, have, more than any other part of his teaching,
contributed to give him a prominent place in the history of philosophy.
"All the objects of human reason and inquiry may naturally be
divided into two kinds, to wit, _relations of ideas_ and _matters
of fact_. Of the first kind are the sciences of geometry, algebra,
and arithmetic, and, in short, every affirmation which is either
intuitively or demonstratively certain. _That the square of the
hypothenuse is equal to the square of the two sides_, is a
proposition which expresses a relation between these two figures.
_That three times five is equal to the half of thirty_, expresses a
relation between these numbers. Propositions of this kind are
discoverable by the mere operation of thought without dependence on
whatever is anywhere existent in the universe. Though there never
were a circle or a triangle in nature, the truths demonstrated by
Euclid would for ever retain their certainty and evidence.
"Matters of fact, which are the second objects of human reason, are
not ascertained in the same manner, nor is an evidence of their
truth, however great, of a like nature with the foregoing. The
contrary of every matter of fact is still possible, because it can
never imply a contradiction, and is conceived by the mind with the
same facility and distinctness, as if ever so conformable to
reality. _That the sun will not rise to-morrow_, is no less
intelligible a proposition, and implies no more contradiction, than
the affirmation, _that it will rise_. We should in vain, therefore,
attempt to demonstrate its falsehood. Were it demonstratively
false, it would imply a contradiction, and could never be
distinctly conceived by the mind."--(IV. pp. 32, 33.)
The distinction here drawn between the truths of geometry and other
kinds of truth is far less sharply indicated in the _Treatise_, but as
Hume expressly disowns any opinions on these matters but such as are
expressed in the _Inquiry_, we may confine ourselves to the latter; and
it is needful to look narrowly into the propositions here laid down, as
much stress has been laid upon Hume's admission that the truths of
mathematics are intuitively and demonstratively certain; in other
words, that they are necessary and, in that respect, differ from all
other kinds of belief.
What is meant by the assertion that "propositions of this kind are
discoverable by the mere operation of thought without dependence on what
is anywhere existent in the universe"?
Suppose that there were no such things as impressions of sight and touch
anywhere in the universe, what idea could we have even of a straight
line, much less of a triangle and of the relations between its sides?
The fundamental proposition of all Hume's philosophy is that ideas are
copied from impressions; and, therefore, if there were no impressions of
straight lines and triangles there could be no ideas of straight lines
and triangles. But what we mean by the universe is the sum of our actual
and possible impressions.
So, again, whether our conception of number is derived from relations of
impressions in space or in time, the impressions must exist in nature,
that is, in experience, before their relations can be perceived. Form
and number are mere names for certain relations between matters of fact;
unless a man had seen or felt the difference between a straight line and
a crooked one, straight and crooked would have no more meaning to him,
than red and blue to the blind.
The axiom, that things which are equal to the same are equal to one
another, is only a particular case of the predication of similarity; if
there were no impressions, it is obvious that there could be no
predicates. But what is an existence in the universe but an impression?
If what are called necessary truths are rigidly analysed, they will be
found to be of two kinds. Either they depend on the convention which
underlies the possibility of intelligible speech, that terms shall
always have the same meaning; or they are propositions the negation of
which implies the dissolution of some association in memory or
expectation, which is in fact indissoluble; or the denial of some fact
of immediate consciousness.
The "necessary truth" A = A means that the perception which is called A
shall always be called A. The "necessary truth" that "two straight lines
cannot inclose a space," means that we have no memory, and can form no
expectation of their so doing. The denial of the "necessary truth" that
the thought now in my mind exists, involves the denial of consciousness.
To the assertion that the evidence of matter of fact, is not so strong
as that of relations of ideas, it may be justly replied, that a great
number of matters of fact are nothing but relations of ideas. If I say
that red is unlike blue, I make an assertion concerning a relation of
ideas; but it is also matter of fact, and the contrary proposition is
inconceivable. If I remember[26] something that happened five minutes
ago, that is matter of fact; and, at the same time, it expresses a
relation between the event remembered and the present time. It is wholly
inconceivable to me that the event did not happen, so that my assurance
respecting it is as strong as that which I have respecting any other
necessary truth. In fact, the man is either very wise or very virtuous,
or very lucky, perhaps all three, who has gone through life without
accumulating a store of such necessary beliefs which he would give a
good deal to be able to disbelieve.
It would be beside the mark to discuss the matter further on the present
occasion. It is sufficient to point out that, whatever may be the
differences, between mathematical and other truths, they do not justify
Hume's statement. And it is, at any rate, impossible to prove, that the
cogency of mathematical first principles is due to anything more than
these circumstances; that the experiences with which they are concerned
are among the first which arise in the mind; that they are so
incessantly repeated as to justify us, according to the ordinary laws of
ideation, in expecting that the associations which they form will be of
extreme tenacity; while the fact, that the expectations based upon them
are always verified, finishes the process of welding them together.
Thus, if the axioms of mathematics are innate, nature would seem to have
taken unnecessary trouble; since the ordinary process of association
appears to be amply sufficient to confer upon them all the universality
and necessity which they actually possess.
Whatever needless admissions Hume may have made respecting other
necessary truths he is quite clear about the axiom of causation, "That
whatever event has a beginning must have a cause;" whether and in what
sense it is a necessary truth; and, that question being decided, whence
it is derived.
With respect to the first question, Hume denies that it is a necessary
truth, in the sense that we are unable to conceive the contrary. The
evidence by which he supports this conclusion in the _Inquiry_, however,
is not strictly relevant to the issue.
"No object ever discovers, by the qualities which appear to the
senses, either the cause which produced it, or the effects which
will arise from it; nor can our reason, unassisted by experience,
ever draw any inference concerning real existence and matter of
fact."--(IV. p. 35.)
Abundant illustrations are given of this assertion, which indeed cannot
be seriously doubted; but it does not follow that, because we are
totally unable to say what cause preceded, or what effect will succeed,
any event, we do not necessarily suppose that the event had a cause and
will be succeeded by an effect. The scientific investigator who notes a
new phenomenon may be utterly ignorant of its cause, but he will,
without hesitation, seek for that cause. If you ask him why he does so,
he will probably say that it must have had a cause; and thereby imply
that his belief in causation is a necessary belief.
In the _Treatise_ Hume indeed takes the bull by the horns:
" ... as all distinct ideas are separable from each other, and as
the ideas of cause and effect are evidently distinct, 'twill be
easy for us to conceive any object to be non-existent this moment
find existent the next, without conjoining to it the distinct idea
of a cause or productive principle."--(I. p. 111.)
If Hume had been content to state what he believed to be matter of fact,
and had abstained from giving superfluous reasons for that which is
susceptible of being proved or disproved only by personal experience,
his position would have been stronger. For it seems clear that, on the
ground of observation, he is quite right. Any man who lets his fancy run
riot in a waking dream, may experience the existence at one moment, and
the non-existence at the next, of phenomena which suggest no connexion
of cause and effect. Not only so, but it is notorious that, to the
unthinking mass of mankind, nine-tenths of the facts of life do not
suggest the relation of cause and effect; and they practically deny the
existence of any such relation by attributing them to chance. Few
gamblers but would stare if they were told that the falling of a die on
a particular face is as much the effect of a definite cause as the fact
of its falling; it is a proverb that "the wind bloweth where it
listeth;" and even thoughtful men usually receive with surprise the
suggestion, that the form of the crest of every wave that breaks,
wind-driven, on the sea-shore, and the direction of every particle of
foam that flies before the gale, are the exact effects of definite
causes; and, as such, must be capable of being determined, deductively,
from the laws of motion and the properties of air and water. So again,
there are large numbers of highly intelligent persons who rather pride
themselves on their fixed belief that our volitions have no cause; or
that the will causes itself, which is either the same thing, or a
contradiction in terms.
Hume's argument in support of what appears to be a true proposition,
however, is of the circular sort, for the major premiss, that all
distinct ideas are separable in thought, assumes the question at issue.
But the question whether the idea of causation is necessary, or not, is
really of very little importance. For, to say that an idea is necessary
is simply to affirm that we cannot conceive the contrary; and the fact
that we cannot conceive the contrary of any belief may be a presumption,
but is certainly no proof, of its truth.
In the well-known experiment of touching a single round object, such as
a marble, with crossed fingers, it is utterly impossible to conceive
that we have not two round objects under them; and, though light is
undoubtedly a mere sensation arising in the brain, it is utterly
impossible to conceive that it is not outside the retina. In the same
way, he who touches anything with a rod, not only is irresistibly led to
believe that the sensation of contact is at the end of the rod, but is
utterly incapable of conceiving that this sensation is really in his
head. Yet that which is inconceivable is manifestly true in all these
cases. The beliefs and the unbeliefs are alike necessary, and alike
erroneous.
It is commonly urged that the axiom of causation cannot be derived from
experience, because experience only proves that many things have causes,
whereas the axiom declares that all things have causes. The syllogism,
"many things which come into existence have causes, A has come into
existence: therefore A had a cause," is obviously fallacious, if A is
not previously shown to be one of the "many things." And this objection
is perfectly sound so far as it goes. The axiom of causation cannot
possibly be deduced from any general proposition which simply embodies
experience. But it does not follow that the belief, or expectation,
expressed by the axiom, is not a product of experience, generated
antecedently to, and altogether independently of, the logically
unjustifiable language in which we express it.
In fact, the axiom of causation resembles all other beliefs of
expectation in being the verbal symbol of a purely automatic act of the
mind, which is altogether extra-logical, and would be illogical, if it
were not constantly verified by experience. Experience, as we have seen,
stores up memories; memories generate expectations or beliefs--why they
do so may be explained hereafter by proper investigation of cerebral
physiology. But, to seek for the reason of the facts in the verbal
symbols by which they are expressed, and to be astonished that it is not
to be found there, is surely singular; and what Hume did was to turn
attention from the verbal proposition to the psychical fact of which it
is the symbol.
"When any natural object or event is presented, it is impossible
for us, by any sagacity or penetration, to discover, or even
conjecture, without experience, what event will result from it, or
to carry our foresight beyond that object, which is immediately
present to the memory and senses. Even after one instance or
experiment, where we have observed a particular event to follow
upon another, we are not entitled to form a general rule, or
foretell what will happen in like cases; it being justly esteemed
an unpardonable temerity to judge of the whole course of nature
from one single experiment, however accurate or certain. But when
one particular species of events has always, in all instances, been
conjoined with another, we make no longer any scruple of
foretelling one upon the appearance of the other, and of employing
that reasoning which can alone assure us of any matter of fact or
existence. We then call the one object _Cause_, the other _Effect_.
We suppose that there is some connexion between them: some power in
the one, by which it infallibly produces the other, and operates
with the greatest certainty and strongest necessity.... But there
is nothing in a number of instances, different from every single
instance, which is supposed to be exactly similar; except only,
that after a repetition of similar instances, the mind is carried
by habit, upon the appearance of one event, to expect its usual
attendant, and to believe that it will exist.... The first time a
man saw the communication of motion by impulse, as by the shock of
two billiard balls, he could not pronounce that the one event was
_connected_, but only that it was _conjoined_, with the other.
After he has observed several instances of this nature, he then
pronounces them to be _connected_. What alteration has happened to
give rise to this new idea of _connexion_? Nothing but that he now
_feels_ those events to be _connected_ in his imagination, and can
readily foresee the existence of the one from the appearance of the
other. When we say, therefore, that one object is connected with
another we mean only that they have acquired a connexion in our
thought, and give rise to this inference, by which they become
proofs of each other's existence; a conclusion which is somewhat
extraordinary, but which seems founded on sufficient
evidence."--(IV. pp. 87-89.)
In the fifteenth section of the third part of the _Treatise_, under the
head of the _Rules by which to Judge of Causes and Effects_, Hume gives
a sketch of the method of allocating effects to their causes, upon
which, so far as I am aware, no improvement was made down to the time of
the publication of Mill's _Logic_. Of Mill's four methods, that of
_agreement_ is indicated in the following passage:--
" ... where several different objects produce the same effect, it
must be by means of some quality which we discover to be common
amongst them. For as like effects imply like causes, we must always
ascribe the causation to the circumstance wherein we discover the
resemblance."--(I. p. 229.)
Next, the foundation of the _method of difference_ is stated:--
"The difference in the effects of two resembling objects must
proceed from that particular in which they differ. For, as like
causes always produce like effects, when in any instance we find
our expectation to be disappointed, we must conclude that this
irregularity proceeds from some difference in the causes."--(I. p.
230.)
In the succeeding paragraph the _method of concomitant variations_ is
foreshadowed.
"When any object increases or diminishes with the increase or
diminution of the cause, 'tis to be regarded as a compounded
effect, derived from the union of the several different effects
which arise from the several different parts of the cause. The
absence or presence of one part of the cause is here supposed to be
always attended with the absence or presence of a proportionable
part of the effect. This constant conjunction sufficiently proves
that the one part is the cause of the other. We must, however,
beware not to draw such a conclusion from a few experiments."--(I.
p. 230.)
Lastly, the following rule, though awkwardly stated, contains a
suggestion of the _method of residues_:--
" ... an object which exists for any time in its full perfection
without any effect, is not the sole cause of that effect, but
requires to be assisted by some other principle, which may forward
its influence and operation. For as like effects necessarily follow
from like causes, and in a contiguous time and place, their
separation for a moment shows that these causes are not complete
ones."--(I. p. 230.)
In addition to the bare notion of necessary connexion between the cause
and its effect, we undoubtedly find in our minds the idea of something
resident in the cause which, as we say, produces the effect, and we call
this something Force, Power, or Energy. Hume explains Force and Power as
the results of the association with inanimate causes of the feelings of
endeavour or resistance which we experience, when our bodies give rise
to, or resist, motion.
If I throw a ball, I have a sense of effort which ends when the ball
leaves my hand; and if I catch a ball, I have a sense of resistance
which comes to an end with the quiescence of the ball. In the former
case, there is a strong suggestion of something having gone from myself
into the ball; in the latter, of something having been received from the
ball. Let any one hold a piece of iron near a strong magnet, and the
feeling that the magnet endeavours to pull the iron one way in the same
manner as he endeavours to pull it in the opposite direction, is very
strong.
As Hume says:--
"No animal can put external bodies in motion without the sentiment
of a _nisus_, or endeavour; and every animal has a sentiment or
feeling from the stroke or blow of an external object that is in
motion. These sensations, which are merely animal, and from which
we can, _a priori_, draw no inference, we are apt to transfer to
inanimate objects, and to suppose that they have some such feelings
whenever they transfer or receive motion."--(IV. p. 91, _note_.)
It is obviously, however, an absurdity not less gross than that of
supposing the sensation of warmth to exist in a fire, to imagine that
the subjective sensation of effort or resistance in ourselves can be
present in external objects, when they stand in the relation of causes
to other objects.
To the argument, that we have a right to suppose the relation of cause
and effect to contain something more than invariable succession,
because, when we ourselves act as causes, or in volition, we are
conscious of exerting power; Hume replies, that we know nothing of the
feeling we call power except as effort or resistance; and that we have
not the slightest means of knowing whether it has anything to do with
the production of bodily motion or mental changes. And he points out, as
Descartes and Spinoza had done before him, that when voluntary motion
takes place, that which we will is not the immediate consequence of the
act of volition, but something which is separated from it by a long
chain of causes and effects. If the will is the cause of the movement of
a limb, it can be so only in the sense that the guard who gives the
order to go on, is the cause of the transport of a train from one
station to another.
"We learn from anatomy, that the immediate object of power in
voluntary motion is not the member itself which is moved, but
certain muscles and nerves and animal spirits, and perhaps
something still more minute and unknown, through which the motion
is successively propagated, ere it reach the member itself, whose
motion is the immediate object of volition. Can there be a more
certain proof that the power by which the whole operation is
performed, so far from being directly and fully known by an inward
sentiment or consciousness, is to the last degree mysterious and
unintelligible? Here the mind wills a certain event: Immediately
another event, unknown to ourselves, and totally different from the
one intended, is produced: This event produces another equally
unknown: Till at last, through a long succession, the desired event
is produced."--(IV. p. 78.)
A still stronger argument against ascribing an objective existence to
force or power, on the strength of our supposed direct intuition of
power in voluntary acts, may be urged from the unquestionable fact, that
we do not know, and cannot know, that volition does cause corporeal
motion; while there is a great deal to be said in favour of the view
that it is no cause, but merely a concomitant of that motion. But the
nature of volition will be more fitly considered hereafter.
FOOTNOTE:
[26] Hume, however, expressly includes the "records of our memory" among
his matters of fact.--(IV. p. 33.)