A Treatise of Human Nature · David Hume
GENERAL INTRODUCTION TO VOL. I.
55. It is clear that here in his very statement of the question Locke begs the answer. If the intuitive certainty is that ‘the idea we _receive from an external object_ is in our minds,’ [1] how is it possible to doubt whether such an object exists and affects our senses? This impossibility of speaking of the simple idea, except as received from an object, may account for Locke’s apparent inconsistency in finding the assurance of the reality of knowledge (under the phrase ‘evidence of the senses’) just in that ‘perception’ which reaches not to intuitive or demonstrative certainty, and only ‘passes under the name of knowledge.’ In the passage just quoted he shows that he is cognizant of the distinction between the simple idea and the perception of an existence corresponding to it, and in consequence distinguishes this perception from proper intuition, but in the very statement of the distinction it eludes him. The simple idea, as he speaks of it, becomes itself, as consciously ‘received from an external object,’ the perception of existence; just as we have previously seen it become the judgment of identity or perception of the ‘agreement of an idea with itself,’ which is his first kind of knowledge. [1] I do not now raise the question, What are here the ideas, which must be immediately perceived to agree or disagree in order to make it a case of ‘intuitive certainty’ or knowledge according to Locke’s definition. See below, paragraphs 59, 101, and 147.
Lively ideas real, because they must be effects of things. 56. In short, with Locke the simple idea, the perception of existence corresponding to the idea, and the judgment of identity, are absolutely merged, and in mutual involution, sometimes under one designation, sometimes under another, are alike presented as the beginning of knowledge. As occasion requires, each does duty for the other. Thus, if the ‘reality of knowledge’ be in question, the simple idea, which is given, is treated as involving the perception of existence, and the reality is established. If in turn this perception is distinguished from the simple idea, and it is asked whether the correspondence between idea and existence is properly matter of knowledge, the simple idea has only to be treated as involving the judgment of identity, which again involves that of existence, and the question is answered. So in the context under consideration (Book IV. chap. ii. sec. 14), after raising the question as to the existence of a thing corresponding to the idea, he answers it by the counter question, ‘whether anyone is not invincibly conscious to himself of a different perception, when he looks on the sun by day, and thinks on it by night; when he actually tastes wormwood, or smells a rose, or only thinks on that savour or odour?
We as plainly find the difference there is between any idea revived in our minds by our own memory, and actually coming into our minds by our senses, as we do between any two distinct ideas.’ The force of the above lies in its appeal to the perception of identity, or--to apply the language in which Locke describes this perception--the knowledge that the idea which a man calls the smell of a rose is the very idea it is. [1] The mere difference in liveliness between the present and the recalled idea, which, as Berkeley and Hume rightly maintained, is the only difference between them as mere ideas, cannot by itself constitute the difference between the knowledge of the presence of a thing answering to the idea and the knowledge of its absence. It can only do this if the more lively idea is _identified_ with past lively ideas as a representation of one and the same thing which ‘agrees with itself’ in contrast to the multiplicity of the sensations, its signs. Only in virtue of this identification can either the liveliness of the idea show that the thing--the sun or the rose--is there, or the want of liveliness that it is not, for without it there would be no thing to be there or not to be there. It is because this identification is what Locke understands by the first sort of perception of agreement between ideas, and because he virtually finds this perception again in the simple idea, that the simple idea is to him the index of reality. But if so, the idea in its primitive simplicity is the sign of a thing that is ever the same in the same relations, and we find the ‘workmanship of the mind,’ its inventions of substance, cause, and relation, in the very rudiments of knowledge.
It is therefore the actual receiving of ideas from without, that gives us notice of the existence of other things, and makes us know that something doth exist at that time without us, which causes that idea in us, though perhaps we neither know nor consider how it does it; for it takes not from the certainty of our senses and the ideas we receive by them, that we know not the manner wherein they are produced; _e.g._ whilst I write this, I have, by the paper affecting my eyes, that idea produced in my mind, which, whatever object causes, I call _white_; by which I know that the quality or accident (_i.e._ whose appearance before my eyes always causes that idea) doth really exist, and hath a being without me. And of this the greatest assurance. I can possibly have, and to which my faculties can attain, is the testimony of my eyes, which are the proper and sole judges of this thing, whose testimony I have reason to rely on, as so certain, that I can no more doubt whilst I write this, that I see white and black, and that something really exists that causes that sensation in me, than that I write and move my hand.’ (Book IV. chap. xi. secs. 1, 2.) Reasons why its testimony must be trusted.
58. Reasons are afterwards given for the assurance that the ‘perceptions’ in question are produced in us by ‘exterior causes affecting our senses.’ The first _(a)_ is, that ‘those that want the organs of any sense never can have the ideas belonging to that sense produced in their mind.’ The next _(b)_, that whereas ‘if I turn my eyes at noon toward the sun, I cannot avoid the ideas which the light or the sun then produces in me;’ on the other hand, ‘when my eyes are shut or windows fast, as I can at pleasure recall to my mind the ideas of light or the sun, which former sensations had lodged in my memory, so I can at pleasure lay them by.’ Again _(c)_, ‘many of those ideas are produced in us with pain which afterwards we remember without the least offence. Thus the pain of heat or cold, when the idea of it is revived in our minds, gives us no disturbance; which, when felt, was very troublesome, and is again, when actually repeated; which is occasioned by the disorder the external object causes in our body, when applied to it.’ Finally (d), ‘our senses in many cases bear witness to the truth of each other’s report, concerning the existence of sensible things without us.
He that sees a fire may, if he doubt whether it be anything more than a bare fancy, feel it too.’ Then comes the conclusion, dangerously qualified: ‘When our senses do actually convey into our understandings any idea, we cannot but be satisfied that there doth something at that time really exist without us, which doth affect our senses, and by them give notice of itself to our apprehensive faculties, and actually produce that idea which we then perceive; and we cannot so far distrust their testimony as to doubt that such collections of simple ideas, as we have observed by our senses to be united together, actually exist together. But this knowledge extends as far as the present testimony of our senses, employed about particular objects, that do then affect them, and no farther. For if I saw such a collection of simple ideas as is wont to be called man, existing together one minute since, and am now alone; I cannot be certain that the same man exists now, since there is no necessary connexion of his existence a minute since with his existence now. By a thousand ways he may cease to be, since I had the testimony of my senses for his existence.’ (Book IV. chap. xi. sec. 9.) How does this account fit Locke’s definition of knowledge?
59. Upon the ‘knowledge of the existence of things,’ thus established, it has to be remarked in the first place that, after all, according to Locke’s explicit statement, it is not properly knowledge. It is ‘an assurance that deserves the name of knowledge’ (Book IV. chap. ii. sec. 14, and xi. sec. 3), yet being neither itself an intuition of agreement between ideas, nor resoluble into a series of such intuitions, the definition of knowledge excludes it. Only if existence were itself an ‘idea,’ would the consciousness of the agreement of the idea with it be a case of knowledge; but to make existence an idea is to make the whole question about the agreement of ideas, as such, with existence, as such, unmeaning. To seek escape from this dilemma by calling the consciousness of the agreement in question an ‘assurance’ instead of knowledge is a mere verbal subterfuge. There can be no assurance of agreement between an idea and that which is no object of consciousness at all. If, however, existence is an object of consciousness, it can, according to Locke, be nothing but an idea, and the question as to the _assurance_ of agreement is no less unmeaning than the question as to the _knowledge_ of it. The raising of the question in fact, as Locke puts it, implies the impossibility of answering it. It cannot be raised with any significance, unless existence is external to and other than an idea. It cannot be answered unless existence is, or is given in, an object of consciousness, _i.e._ an idea.
Locke’s account of the testimony of sense renders his question as to its veracity superfluous. 60. As usual, Locke disguises this difficulty from himself, because in answering the question he alters it. The question, _as he asks it_, is whether, given the idea, we can have posterior assurance of something else corresponding to it. The question, _as he answers it_, is whether the idea includes the consciousness of a real thing as a constituent; and the answer consists in the simple assertion, variously repeated, that it does. It is clear, however, that this answer to the latter question does not answer, but renders unmeaning, the question as it is originally asked. If, according to Locke’s own showing, there is nowhere for anything to be found by us but in our ‘ideas’ or our consciousness--if the _thing_ is given in and with the idea, so that the idea is merely the thing _ex parte nostrâ_--then to ask if the idea agrees with the thing is as futile as to ask whether hearing agrees with sound, or the voice with the words it utters. That the thing is so given is implied throughout Locke’s statement of the ‘assurance we have of the existence of material beings,’ as well as of the confirmations of this assurance. If the ‘idea which I call white’ means the knowledge that ‘the property or accident (_i.e._ whose appearance before my eyes always causes that idea) doth really exist and hath a being without me,’ then consciousness of existence--outward, permanent, substantive, and causative existence--is involved in the idea, and no ulterior question of agreement between idea and existence can properly arise. But unless the simple idea is so interpreted, the senses have no testimony to give. If it is so interpreted, no extraneous ‘reason to rely upon the testimony’ can be discovered, for such reason can only be a repetition of the testimony itself.
Confirmations of the testimony turn upon the distinction between ‘impression’ and ‘idea’. 61. This becomes clearer upon a view of the confirmations of the testimony, as Locke gives them. They all, we may remark by the way, presuppose a distinction between the simple idea as originally represented and the same as recalled or revived. This distinction, fixed by the verbal one between ‘impression’ and ‘idea,’ we shall find constantly maintained and all-important in Hume’s system; but in Locke, though upon it (as we shall see) rests his distinction between real and nominal essence and his confinement of general knowledge to the latter, it seems only to turn up as an afterthought. In the account of the reality and adequacy of ideas it does not appear at all. There the distinction is merely between the simple idea, as such, and the complex, as such, without any further discrimination of the simple idea as originally produced from the same as recalled. So, too, in the opening account of the reception of simple ideas (Book II. chap. xii. sec. 1), ‘Perception,’ ‘Retention,’ and ‘Discerning’ are all reckoned together as alike forms of the _passivity_ of the mind, in contrast with its activity in combination and abstraction, though retention and discerning have been previously described in terms which imply activity. In the ‘confirmations’ before us, however, the distinction between the originally produced and the revived is essential.
They depend on language which presupposes the ascription of sensation to an outward cause. 62. The first turns upon the impossibility of producing an idea _de novo_ without the action of sensitive organs; the two next upon the difference between the idea as produced through these organs and the like idea as revived at the will of the individual. It is hence inferred that the idea as originally produced is the work of a thing, which must exist _in rerum naturâ_, and by way of a fourth ‘confirmation’ the man who doubts this in the case of one sensation is invited to try it in another. If, on seeing a fire, he thinks it ‘bare fancy,’ _i.e._ doubts whether his idea is caused by a thing, let him put his hand into it. This last ‘confirmation’ need not be further noticed here, since the operation of a producing thing is as certain or as doubtful for one sensation as for another. [1] Two certainties are not more sure than one, nor can two doubts make a certainty. The other ‘confirmations’ alike lie in the words ‘product’ and ‘organ.’ A man has a certain ‘idea:’ afterwards he has another like it, but differing in liveliness and in the accompanying pleasure or pain.
If he already has, or if the ideas severally bring with them, the idea of a producing outward thing to which parts of his body are organs, on the one hand, and of a self ‘having power’ on the other, then the liveliness, and the accompanying pleasure or pain, may become indications of the action of the thing, as their absence may be so of the action of the man’s self; but not otherwise. Locke throughout, in speaking of the simple ideas as produced or recalled, implies that they carry with them the consciousness of a cause, either an outward thing or the self, and only by so doing can he find in them the needful ‘confirmations’ of the ‘testimony of the senses.’ This testimony is confirmed just because it distinguishes of itself between the work of ‘nature,’ which is real, and the work of the man, which is a fiction. In other words, the confirmation is nothing else than the testimony itself--a testimony which, as we have seen, since it supposes consciousness, as such, to be consciousness _of a thing_, eliminates by anticipation the question as to the agreement of consciousness with things, as with the extraneous. [1] To feel the object, in the sense of touching it, had a special significance for Locke, since touch with him was the primary ‘revelation’ of body, as the solid. More will be said of this when we come to consider his doctrine of ‘real essence,’ as constituted by primary qualities of body. See below, paragraph 101.
This ascription means the clothing of sensation with invented relations. 63. The distinction between the real and the fantastic, according to the passages under consideration, thus depends upon that between the work of nature and the work of man. It is the confusion between the two works that renders the fantastic possible, while it is the consciousness of the distinction that sets us upon correcting it. Where all is the work of man and professes to be no more, as in the case of ‘mixed modes,’ there is no room for the fantastic (Book II. chap. xxx. sec. 4, and Book IV. chap. iv. sec. 7); and where there is ever so much of the fantastic, it would not be so for us, unless we were conscious of a ‘work of nature,’ to which to oppose it. But on looking a little closer we find that to be conscious of an idea as the work of nature, in opposition to the work of man, is to be conscious of it under relations which, according to Locke, are the inventions of man. It is nothing else than to be conscious of it as the result of ‘something having power to produce it’ (Book II. chap. xxxi. sec. 2), _i.e._ of a substance, to which it is related as a quality.
‘Nature’ is just the ‘something we know not what,’ which is substance according to the ‘_abstract_ idea’ thereof. Producing ideas, it exercises powers, as it essentially belongs to substance to do, according to our _complex_ idea of it. (Book II. chap, xxiii. secs. 9, 10.) But substance, according to Locke, whether as abstract or complex idea, is the ‘workmanship of the mind,’ and power, as a relation (Book II. chap. xxi. sec. 3, and chap. xxv. sec. 8), ‘is not contained in the real existence of things.’ Again, the idea of substance, as a source of power, is the same as the idea of cause. ‘Whatever is considered by us to operate to the producing any particular simple idea, which did not before exist, hath thereby in our minds the relation of a cause.’ (Book II. chap. xxvi. sec. 1.) But the idea of cause is not one ‘that the mind has of things as they are in themselves,’ but one that it gets by its own act in ‘bringing things to, and setting them by, one another.’ (Book II. chap. xxv. sec. 1.) Thus it is with the very ideas, which are the workmanship of man, that the simple idea has to be clothed upon, in order to ‘testify’ to its being real, _i.e._ (in Locke’s sense) not the work of man.
What is meant by restricting the testimony of sense to _present_ existence? 64. Thus invested, the simple idea has clearly lost its simplicity. It is not the momentary, isolated consciousness, but the representation of a thing determined by relations to other things in an order of nature, and causing an infinite series of resembling sensations to which a common name is applied. Thus in all the instances of sensuous testimony mentioned in the chapter before us, it is not really a simple sensation that is spoken of, but a sensation referred to a thing--not a mere smell, or taste, or sight, or feeling, but the smell of a rose, the taste of a pine-apple, the sight of the sun, the feeling of fire. (Book IV. chap. xi. secs. 4-7.) Immediately afterwards, however, reverting or attempting to revert to his strict doctrine of the mere individuality of the simple idea, he says that the testimony of the senses is a ‘present testimony employed about particular objects, that do then affect them,’ and that sensitive knowledge extends no farther than such testimony. This statement, taken by itself, is ambiguous. Does it mean that sensation testifies to the momentary presence to the individual of a continuous existence, or is the existence itself as momentary as its presence to sense? The instance that follows does not remove the doubt.
‘If I saw such a collection of simple ideas as is wont to be called _man_, existing together one minute since, and am now alone; I cannot be certain that the same man exists now, since there is no necessary connection of his existence a minute since with his existence now.’ (Book IV. chap. xi. sec. 9.) At first sight, these words might seem to decide that the existence is merely coincident with the presence of the sensation--a decision fatal to the distinction between the real and fantastic, since, if the thing is only present with the sensation, there can be no combination of qualities in reality other than the momentary coincidence of sensations in us. Memory or imagination, indeed, might recall these in a different order from that in which they originally occurred; but, if this original order had no being after the occurrence, there could be no ground for contrasting it with the order of reproduction as the real with the merely apparent. Such restriction, if maintained, would render the testimony unmeaning.
65. In the very sentence, however, where Locke restricts the testimony of sensation to existence present along with it, he uses language inconsistent with this restriction. The particular existence which he instances as ‘testified to’ is that of ‘such a collection of simple ideas as is wont to be called man.’ But these ideas can only be present in succession. (See Book II. chap. vii. sec. 9, and chap. xiv. sec. 3.) Even the surface of the man’s body can only be taken in by successive acts of vision; and, more obviously, the states of consciousness in which his qualities of motion and action are presented occupy separate times. If then sensation only testifies to an existence present along with it, how can it testify to the co-existence (say) of an erect attitude, of which I have a present sight, with the risibility which I saw a minute ago? How can the ‘collection of ideas wont to be called man,’ _as co-existing_, be formed at all? and, if it cannot, how can the present existence of an object so-called be testified to by sense any more than the past?
The same doctrine, which is fatal to the supposition of ‘a necessary connexion between the man’s existence a minute since and his existence now,’ is in fact fatal to the supposition of his existence as a complex of qualities at all. It does not merely mean that, for anything we know, the man may have died. Of course he may, and yet there may be continuity of existence according to natural laws, though not one for which we have the testimony of present sense, between the living body and the dead. What Locke had in his mind was the notion that, as existence is testified to only by present sensation, and each sensation is merely individual and momentary, there could be no testimony to the continued existence of anything. He could not, however, do such violence to the actual fabric of knowledge as would have been implied in the logical development of this doctrine, and thus he allowed himself to speak of sense as testifying to the co-existence of sensible qualities in a thing, though the individual sensation could only testify to the presence of one at a time, and could never testify to their _nexus_ in a common cause at all. This testimony to co-existence in a present thing once admitted, he naturally allowed himself in the further assumption that the testimony, on its recurrence, is a testimony to the same co-existence and the same thing. The existence of the same man (he evidently supposes), to which sensation testified an hour ago, may be testified to by a like sensation now. This means that resemblance of sensation becomes identity of a thing--that like sensations occurring at different times are interpreted as representing the same thing, which continuously exists, though not testified to by sense, between the times.
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