A Treatise of Human Nature · David Hume
GENERAL INTRODUCTION TO VOL. I.
That they are related as effects and causes, it would seem, we know; and that the ‘causes work steadily, and effects constantly flow from them,’ we know also; but ‘their connexions and dependencies are not discoverable in our ideas’ (Book IV. chap. iii. sec. 29). That, if discoverable in our ideas, just because there discovered, the connexion would not be a real co-existence, Locke never expressly says. He does not so clearly articulate the antithesis between relations of ideas and matters of fact. If he had done so, he must also have excluded from real existence those abstract ideas of body which constitute the scanty knowledge of it that according to him we do possess (Book IV. chap. iii. sec. 24). He is more disposed to sigh for discoveries that would make physics capable of the same general certainty as mathematics, than to purge the former of those mathematical propositions--really true only because having no reference to reality--which to him formed the only scientific element in them. What knowledge it can afford, according to Locke.
122. The ambiguity of his position will become clearer if we resort to his favourite ‘instances in gold.’ The proposition, ‘all gold is soluble in aqua regia,’ is certainly true, if such solubility is included in the complex idea which the word ‘gold’ stands for, and if such inclusion is all that the proposition purports to state. It is equally certain and equally trifling with the proposition, ‘a centaur is four-footed.’ But, in fact, as a proposition concerning substance, it purports to state more than this, viz. that a ‘body whose complex idea is made up of yellow, very weighty, ductile, fusible, and fixed,’ is always soluble in aqua regia. In other words, it states the invariable co-existence in a body of the complex idea, ‘solubility in aqua regia,’ with the group of ideas indicated by ‘gold.’ Thus understood--as instructive or synthetical--it has not the certainty which would belong to it if it were ‘trifling,’ or analytical, ‘since we can never, from the consideration of the ideas themselves, with certainty affirm’ their co-existence (Book IV. chap. vi. sec 9).
If we see the solution actually going on, or can recall the sight of it by memory, we can affirm its co-existence with the ideas in question in that ‘bare instance;’ and thus, on the principle that ‘whatever ideas have once been united in nature may be so united again’ (Book IV. chap. iv. sec. 12), infer a capacity of co-existence between the ideas, but that is all. ‘Constant observation may assist our judgments in guessing’ an invariable actual co-existence (Book IV. chap. viii. sec. 9); but beyond guessing we cannot get. If our instructive proposition concerning co-existence is to be general it must remain problematical. It is otherwise with mathematical propositions. ‘If the three angles of a triangle were once equal to two right angles, it is certain that they always will be so;’ but only because such a proposition concerns merely ‘the habitudes and relations of ideas.’ ‘If the perception that the same ideas will eternally have the same habitudes and relations be not a sufficient ground of knowledge, there could be no knowledge of general propositions in mathematics; for no mathematical demonstration could be other than particular: and when a man had demonstrated any proposition concerning one triangle and circle, his knowledge would not reach beyond that particular diagram’ (Book IV. chap. i. sec. 9). Not the knowledge which is now supposed to be got by induction. Yet more than Locke was entitled to suppose it could give.
123. To a reader, fresh from our popular treatises on Logic, such language would probably at first present no difficulty. He would merely lament that Locke, as a successor of Bacon, was not better acquainted with the ‘Inductive methods,’ and thus did not understand how an observation of co-existence in the bare instance, if the instance be of the right sort, may warrant a universal affirmation. Or he may take the other side, and regard Locke’s restriction upon general certainty as conveying, not any doubt as to the validity of the inference from an observed case to all cases where the conditions are ascertainably the same, but a true sense of the difficulty of ascertaining in any other case that the conditions are the same. On looking closer, however, he will see that, so far from Locke’s doctrine legitimately allowing of such an adaptation to the exigencies of science, it is inconsistent with itself in admitting the reality of most of the conditions in the case supposed to be observed, and thus in allowing the real truth even of the singular proposition. This purports to state, according to Locke’s terminology, that certain ‘ideas’ do now or did once co-exist in a body.
But the ideas, thus stated to co-exist, according to Locke’s doctrine that real existence is only testified to by actual present sensation, differ from each other as that which _really_ exists from that which does not. In the particular experiment of gold being solved in aqua regia, from the complex idea of solubility an indefinite deduction would have to be made for qualification by ideas retained in the understanding before we could reach the present sensation; and not only so, but the group of ideas indicated by ‘gold,’ to whose co-existence with solubility the experiment is said to testify, as Locke himself says, form merely a nominal essence, while the body to which we ascribe this essence is something which we ‘accustom ourselves to suppose,’ not any ‘parcel of matter’ having a real existence in nature. [1] In asserting the co-existence of the ideas forming such a nominal essence with the actual sensation supposed to be given in the experiment, we change the meaning of ‘existence,’ between the beginning and end of the assertion, from that according to which all ideas exist to that according to which existence has no ‘connexion with any other of our ideas but those of ourselves and God,’ but is testified to by present sensation.
But if real existence is such that the relations of ideas, called primary qualities of matter, constitute it, and the qualities included in our nominal essences are its copies or effects, then, as on the one side our complex ideas of substances only fail of reality through want of fulness, or through mistakes in the process by which they are ‘taken from things,’ so, on the other side, the mental truth of mathematical propositions need only fail to be real because the ideas, whose relations they state, are considered in abstraction from conditions which qualify them in real existence. ‘If it is true of the idea of a triangle that its three angles equal two right ones, it is true also of a triangle, wherever it really exists’ (Book IV. chap. iv. sec. 6). There is, then, no incompatibility between the idea and real existence. Mathematical ideas might fairly be reckoned, like those of substances, to be taken from real existence; but though, like these, inadequate to its complexity, to be saved from the necessary infirmities which attach to ideas of substances because not considered as so taken, but merely as in the mind. There is language about mathematics in Locke that may be interpreted in this direction, though his most explicit statements are on the other side. It is not our business to adjust them, but merely to point out the opposite tendencies between which a clear-sighted operator on the material given by Locke would find that he had to choose.
Two lines of thought in Locke, between which a follower would have to choose. 125. On the one hand there is the identification of real existence with the momentary sensible event. This view, of which the proper result is the exclusion of predication concerning real existence altogether, appears in Locke’s restriction of such predication to the singular proposition, and in his converse assertion that propositions of mathematical certainty ‘concern not existence’ (Book IV. chap. iv. sec. 8). The embarrassment resulting from such a doctrine is that it leads round to the admission of the originativeness of thought and of the reality of its originations, with the denial of which it starts. [1] It leads Locke himself along a track, which his later followers scarcely seem to have noticed, when he treats the ‘never enough to be admired discoveries of Mr. Newton’ as having to do merely with the relations of ideas in distinction from things, and looks for a true extension of knowledge--neither in syllogism which can yield no instructive, nor in experiment which can yield no general, certainty--but only in a further process of ‘singling out and laying in order intermediate ideas,’ which are ‘real as well as nominal essences of their species,’ because they have no reference to archetypes elsewhere than in the mind (Book IV. chap. vii. sec. 11, and Book IV. chap. xii. sec. 7).
On the other hand there is the notion that ideas, without distinction between ‘actual sensation’ and ‘idea in the mind,’ are taken from permanent things, and are real if correctly so taken. From this it results that propositions, universally true as representing a necessary relation between ideas of primary qualities, are true also of real existence; and that an extension of such real certainty through the discovery of a necessary connexion between ideas of primary and those of secondary qualities, though scarcely to be hoped for, has no inherent impossibility. It is this notion, again, that unwittingly gives even that limited significance to the particular experiment which Locke assigns to it, as indicating a co-existence between ideas present as sensations and those which can only be regarded as in the mind. Nor is it the intrinsic import so much as the expression of this notion that is altered when Locke substitutes an order of nature for substance as that in which the ideas co-exist.
In his Fourth Book he so far departs from the doctrine implied in his chapters on the reality and adequacy of ideas and on the names of substances, as to treat the notion of several single subjects in which ideas co-exist (which he still holds to be the proper notion of substances), as a fiction of thought. There are no such single subjects. What we deem so are really ‘retainers to other parts of nature.’ ‘Their observable qualities, actions, and powers are owing to something without them; and there is not so complete and perfect a part that we know of nature, which does not owe the being it has, and the excellencies of it, to its neighbours’ (Book IV. chap. vi. sec. 11). As thus conceived of, the ‘objective order’ which our experience represents is doubtless other than that collection of fixed separate ‘things,’ implied in the language about substances which Locke found in vogue, but it remains an objective order still--an order of ‘qualities, actions, and powers’ which no multitude of sensible events could constitute, but apart from which no sensible event could have such significance as to render even a singular proposition of real truth possible. [1] See above, paragraph 117, sub. fin. Transition to doctrine of God and the soul.
126. It remains to inquire how, with Locke, the ideas of self and God escape subjection to those solvents of reality which, with more or less of consistency and consciousness, he applied to the conceptions on which the science of nature rests. Such an enquiry forms the natural transition to the next stage in the history of his philosophy. It was Berkeley’s practical interest in these ideas that held him back from a development of his master’s principles, in which he would have anticipated Hume, and finally brought him to attach that other meaning to the ‘new way of ideas’ faintly adumbrated in the later sections of his ‘Siris,’ which gives to Reason the functions that Locke had assigned to Sense. Thinking substance--source of the same ideas as outer substance.
127. The dominant notion of the self in Locke is that of the inward substance, or ‘substratum of ideas,’ co-ordinate with the outward, ‘wherein they do subsist, and from which they do result.’ ‘Sensation convinces that there are solid extended substances, and reflection that there are thinking ones’ (Book II. chap, xxiii. sec. 29). We have already seen how, without disturbance from his doctrine of the fictitiousness of universals, he treats the simple idea as carrying with it the distinction of outward and inward, or relations severally to a ‘thing’ and to a ‘mind.’ It reports itself ambiguously as a quality of each of these separate substances. It is now, or was to begin with, the result of an outward thing ‘actually operating upon us;’ for ‘of simple ideas the mind cannot make one to itself:’ on the other hand, it is a ‘perception,’ and perception is an ‘operation of the mind.’ In other words it is at once a modification of the mind by something of which it is consciously not conscious, and a modification of the mind by itself--the two sources of one and the same modification being each determined only as the contradictory of the other. Thus, when we come to probe the familiar metaphors under which Locke describes Reflection, as a ‘fountain of ideas’ other than sensation, we find that the confusions which we have already explored in dealing with the ideas of sensation recur under added circumstances of embarrassment. Not only does the simple idea of reflection, like that of sensation, turn out to be already complicated in its simplicity with the superinduced ideas of cause and relation, but the causal substance in question turns out to be one which, from being actually nothing, becomes something by acting upon itself; while all the time the result of this action is indistinguishable from that ascribed to the opposite, the external, cause.
Of which substance is perception the effect? 128. To a reader to whom Locke’s language has always seemed to be--as indeed it is--simply that of common sense and life, in writing the above we shall seem to be creating a difficulty where none is to be found. Let us turn, then, to one of the less prolix passages, in which the distinction between the two sources of ideas is expressed: ‘External objects furnish the mind with the ideas of sensible qualities, which are all those different perceptions they produce in us; and the mind furnishes the understanding with ideas of its own operations’ (Book II. chap. i. sec. 5). We have seen already that with Locke perception and idea are equivalent terms. It only needs further to be pointed out that no distinction can be maintained between his usage of ‘mind’ and of ‘understanding,’ [1] and that the simple ideas of the mind’s own operations are those of perception and power, which must be given in and with every idea of a sensible quality.’ [2] Avoiding synonyms, then, and recalling the results of our examination of the terms involved in the first clause of the passage before us, we may re-write the whole thus: ‘Creations of the mind, which yet are external to it, produce in it those perceptions of their qualities which they do produce; and the mind produces in itself the perception of these, its own, perceptions.’
The ‘outer sense’ is only an outer sense at all so far as feelings, by themselves neither outward nor inward, are by the mind referred to a thing or cause which ‘the mind supposes;’ and only thus have its reports a prerogative of reality over the ‘fantasies,’ supposed merely of the mind. Meanwhile, unable to ignore the subjective side of self-consciousness, Locke has to put an inward experience as a separate, but co-ordinate, source of knowledge alongside of the outer. But this inward experience, simply as a succession of feelings, does not differ from the outer: it only so differs as referred to that very ‘thinking thing,’ called the mind, which by its supposition of causal substance has converted feeling into an experience of an outer thing. ‘Mind’ thus, by the relations which it ‘invents,’ constitutes both the inner and outer, and yet is treated as itself the inner ‘substratum which it accustoms itself to suppose.’ It thus becomes the creature of its own suppositions. Nor is this all. This, indeed, is no more than the fate which it must suffer at the hands of every philosopher who, in Kantian language, brings the source of the Categories under the Categories. But with Locke the constitution of the outer world by mental supposition, however uniformly implied, is always ignored; and thus mind, as the inward substance, is not only the creature of its own suppositions, but stands over against a real existence, of which the reality is held to consist just in its being the opposite of all such suppositions: while, after all, the effect of these mutually exclusive causes is one and the same experience, one and the same system of sequent and co-existent ideas.
To get rid of the inner source of ideas in favour of the outer would be false to Locke. 130. Is it then a case of _joint_-effect? Do the outer and inner substances combine, like mechanical forces, to produce the psychical result? Against such a supposition a follower of Locke would find not only the language of his master, with whom perception appears _indifferently_ as the result of the outer or inner cause, but the inherent impossibility of analysing the effect into separate elements. The ‘Law of Parsimony,’ then, will dictate to him that one or other of the causes must be dispensed with; nor, so long as he takes Locke’s identification of the outward with the real for granted, will he have much doubt as to which of the two must go. To get rid of the causality of mind, however, though it might not be untrue to the tendency of Locke, would be to lose sight of his essential merit as a formulator of what everyone thinks, which is that, at whatever cost of confusion or contradiction, he at least formulates it fully. In him the ‘Dialectic,’ which popular belief implicitly involves, goes on under our eyes. If the primacy of self-conscious thought is never recognized, if it remains the victim of its own misunderstood creations, there is at least no attempt to disguise the unrest which attaches to it in this self-imposed subjection.
The mind, which Locke opposes to matter, perpetually shifting. 131. We have already noticed how the inner ‘tablet,’ on which the outer thing is supposed to act, is with Locke perpetually receding. [1] It is first the brain, to which the ‘motion of the outward parts’ must be continued in order to constitute sensation (Book II. chap. ix. sec. 3). Then perception is distinguished from sensation, and the brain itself, as the subject of sensation, becomes the outward in contrast with the understanding as the subject of perception. [2] Then perception, from being simply a reception, is converted into an ‘operation,’ and thus into an efficient of ideas. The ‘understanding’ itself, as perceptive, is now the outward which makes on the ‘mind,’ as the inner ‘tablet,’ that impression of its own operation in perception which is called an idea of reflection. [3] Nor does the regressive process--the process of finding a mind within the mind--stop here, though the distinction of inner and outer is not any further so explicitly employed in it. From mind, as receptive of, and operative about, ideas, _i.e._ consciousness, is distinguished mind as the ‘substance within us’ of which consciousness is an ‘operation’ that it sometimes exercises, sometimes (_e.g._ when it sleeps) does not (Book II. chap. i. secs. 10-12); and from this thinking substance again is distinguished the man who ‘finds it in himself and carries it about with him in a coach or on horseback (Book II. chap, xxiii. sec. 20)--the person, ‘consisting of soul and body,’ who is prone to sleep and in sound sleep is unconscious, but whose personal identity strangely consists in sameness of consciousness, sameness of an occasional operation of part of himself. [3]
132. In the history of subsequent philosophy two typical methods have appeared of dealing with this chaos of antinomies. One, which we shall have to treat at large in writing of Hume, affects to dispose of both the outward and the inward synthesis--both of the unity of feelings in a subject matter and of their unity in a subject mind--as ‘fictions of thought.’ This method at once suggests the vital question whether a mind which thus invents has been effectively suppressed--whether, indeed, the theory can be so much as stated without a covert assumption of that which it claims to have destroyed. The other method, of which Kant is the parent, does not attempt to efface the apparent contradictions which beset the ‘relation between mind and matter;’ but regarding them as in a certain sense inevitable, traces them to their source in the application to the thinking Ego itself of conceptions, which it does indeed constitute in virtue of its presence to phenomena given under conditions of time, but under which for that very reason it cannot itself be known.
It is in virtue of the presence of the self-conscious unit to the manifold of feeling, according to this doctrine, that the latter becomes an order of definite things, each external to the other; and it is only by a false inclusion within this order of that which constitutes it that the Ego itself becomes a ‘thinking thing’ with other things outside it. The result of such inclusion is that the real world, which it in the proper sense makes, becomes a reality external to it, yet apart from which it would not be actually anything. Thus with Locke, though the mind has a potential existence of its own, it is experience of ‘things without it’ that ‘furnishes’ it or makes it what it actually is. But the relation of such outer things to the mind cannot be spoken of without contradiction. If supposed outward as bodies, they have to be brought within consciousness as objects of sensation; if supposed outward as sensation, they have to be brought within consciousness--to find a home in the understanding--as ideas of sensation. Meanwhile the consideration returns that after all the ‘thinking thing’ contributes something to that which it thinks about; and, this once admitted, it is as impossible to limit its work on one side as that of the outer thing on the other. Each usurps the place of its opposite. Thus with Locke the understanding produces effects on itself, but the product is one and the same ‘perception’ otherwise treated as an effect of the outer world. One and the same self-consciousness, in short, [1] involving the correlation of subject and object, becomes the result of two separate ‘things,’ each exclusive of the other, into which the opposite poles of this relation have been converted--the extended thing or ‘body’ on the one side, and the thinking thing or ‘mind’ on the other.
134. Just, then, as Locke’s conception of outward reality grows under his hands into a conception of nature as a system of relations which breaks through the limitations of reality as constituted by mere _individua_, so it is with the self, as he conceived it. It is not a simple idea. It is not one of the train that is for ever passing, ‘one going and another coming,’ for it looks on this succession as that which it experiences, being itself the same throughout the successive differences (Book II. chap. vii. sec. 9, and chap. xxvii. sec. 9). As little can it be adjusted to any of the conditions of real ‘things,’ thinking or unthinking, which he ordinarily recognises. It has no ‘particularity in space and time.’ That which is past in ‘reality’ is to it present. It is ‘in its nature indifferent to any parcel of matter.’ It is the same with itself yesterday and to-day, here and there. That ‘with which its consciousness can join itself is one self with it,’ and it can so join itself with substances apart in space and remote in time (Book II. chap, xxvii. secs. 9, 13, 14, 17). For speaking of it as eternal, indeed, we could find no warrant in Locke.
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