[3] Cf. Book IV. chap. iii. sec. 29; Book IV. chap. vi. sec. 14; Book IV. chap. xi. sec. 11.
How then is science of nature possible?
83. We thus come upon the crucial antithesis between relations of ideas and matters of fact, with the exclusion of general certainty as to the latter, which was to prove such a potent weapon of scepticism in the hands of Hume. Of its incompatibility with recognized science we can have no stronger sign than the fact that, after more than a century has elapsed since Locke’s premisses were pushed to their legitimate conclusion, the received system of logic among us is one which, while professing to accept Locke’s doctrine of essence, and with it the antithesis in question, throughout assumes the possibility of general propositions as to matters of fact, and seeks in their methodical discovery and proof that science of nature which Locke already ‘suspected’ to be impossible. (Book IV. chap. xii. sec. 10.)
No ‘uniformities of phenomena’ can be known.
84. That, so far as any inference from past to future uniformities is necessary to the science of nature, his doctrine does more than justify such ‘suspicion,’ is plain enough. Does it, however, leave room for so much as a knowledge of past uniformities of fact, in which the natural philosopher, accepting the doctrine, might probably seek refuge? At first sight, it might seem to do so. ‘As, when our senses are actually employed about any object, we do know that it does exist; so by our memory we may be assured that heretofore things that affected our senses have existed—and thus we have knowledge of the past existence of several things, whereof our senses having informed us, our memories still retain the ideas.’ (Book IV. chap. xi. sec. 11.) Let us see, however, how this knowledge is restricted. ‘Seeing water at this instant, it is an unquestionable truth to me that water doth exist; and remembering that I saw it yesterday, it will also be always true, and as long as my memory retains it, always an undoubted proposition to me, that water did exist the 18th of July, 1688; as it will also be equally true that a certain number of very fine colours did exist, which at the same time I saw on a bubble of that water; but being now quite out of sight both of the water and bubbles too, it is no more certainly known to me that the water doth now exist, than that the bubbles and colours therein do so; it being no more necessary that water should exist to-day because it existed yesterday, than that the colours or bubbles exist to-day because they existed yesterday.’ (Ibid.)
Locke not aware of the full effect of his own doctrine …
85. The result is that though I may enumerate a multitude of past matters-of-fact about water, I cannot gather them up in any general statement about it as a real existence. So soon as I do so, I pass from water as a real existence to its ‘nominal essence,’ i.e., to the ideas retained in my mind and put together in a fictitious substance, to which I have annexed the name ‘water.’ If we proceed to apply this doctrine to the supposed past matters-of-fact themselves, we shall find these too attenuating themselves to nonentity. Subtract in every case from the ‘particular existence’ of which we have ‘sensitive knowledge’ the qualification by ideas which, as retained in the mind, do not testify to a present real existence, and what remains? There is a certainty, according to Locke (Book IV. chap. xi. sec. 11), not, indeed, that water exists to-day because it existed yesterday—this is only ‘probable’—but that it has, as a past matter-of-fact, at this time and that ‘continued long in existence,’ because this has been ‘observed;’ which must mean (Book IV. chap. ii. secs. 1, 5, and 9), because there has been a continued ‘actual sensation’ of it. ‘Water,’ however, is a complex idea of a substance, and of the elements of this complex idea those only which at any moment are given in ‘actual sensation’ may be accounted to ‘really exist.’ First, then, must disappear from reality the ‘something,’ that unknown substratum of ideas, of which the idea is emphatically ‘abstract.’ This gone, we naturally fall back upon a fact of co-existence between ideas, as being a reality, though the ‘thing’ be a fiction. But if this co-existence is to be real or to represent a reality, the ideas between which it obtains must be ‘actual sensations.’ These, whatever they may be, are at least opposed by Locke to ideas retained in the mind, which only form a nominal essence. But it is the association of such nominal essence, in the supposed observation of water, with the actual sensation that alone gives the latter a meaning. Set this aside as unreal, and the reality, which the sensation reveals, is at any rate one of which nothing can be said. It cannot be a relation between sensations, for such relation implies a consideration of them by the mind, whereby, according to Locke, they must cease to be ‘real existences.’ (Book II. chap. xxv. sec. 1.) It cannot even be a single sensation as continuously observed, for every present moment of such observation has at the next become a past, and thus the sensation observed in it has lost its ‘actuality,’ and cannot, as a ‘real existence,’ qualify the sensation observed in the next. Restrict the ‘real existence,’ in short, as Locke does, to an ‘actual present sensation,’ which can only be defined by opposition to an idea retained in the mind, and at every instant of its existence it has passed into the mind and thus ceased really to exist. Reality is in perpetual process of disappearing into the unreality of thought. No point can be fixed either in the flux of time or in the imaginary process from ‘without’ to ‘within’ the mind, on the one side of which can be placed ‘real existence,’ on the other the ‘mere idea.’ It is only because Locke unawares defines to himself the ‘actual sensation’ as representative of a real essence, of which, however, according to him, as itself unknown, the presence is merely inferred from the sensation, that the ‘actual sensation’ itself is saved from the limbo of nominal essence, to which ideas, as abstract or in the mind, are consigned. Only, again, so far as it is thus illogically saved, are we entitled to that distinction between ‘facts’ and ‘things of the mind,’ which Locke once for all fixed for English philosophy.
… which is to make the real an abstract residuum of consciousness.
86. By this time we are familiar with the difficulties which this antithesis has in store for a philosophy which yet admits that it is only in the mind or in relation to consciousness—in one word, as ‘ideas’—that facts are to be found at all, while by the ‘mind’ it understands an abstract generalization from the many minds which severally are born and grow, sleep and wake, with each of us. The antithesis itself, like every other form in which the impulse after true knowledge finds expression, implies a distinction between the seeming and the real; or between that which exists for the consciousness of the individual and that which really exists. But outside itself consciousness cannot get. It is there that the real must, at any rate, manifest itself, if it is to be found at all. Yet the original antithesis between the mind and its unknown opposite still prevails, and in consequence that alone which, though indeed in the mind, is yet given to it by no act of its own, is held to represent the real. This is the notion which dominates Locke. He strips from the formed content of consciousness all that the mind seems to have done for itself, and the abstract residuum, that of which the individual cannot help being conscious at each moment of his existence, is or ‘reports’ the real, in opposition to the mind’s creation. This is Feeling; or more strictly—since it exists, and whatever does so must exist as one in a number (Book II. chap. vii. sec. 7)—it is the multitude of single feelings, ‘each perishing the moment it begins’ (Book II. chap, xxvii. sec. 2), from which all the definiteness that comes of composition and relation must be supposed absent. Thus, in trying to get at what shall be the mere fact in detachment from mental accretions, Locke comes to what is still consciousness, but the merely indefinite in consciousness. He seeks the real and finds the void. Of the real as outside consciousness nothing can be said; and of that again within consciousness, which is supposed to represent it, nothing can be said.
Ground of distinction between actual sensation and ideas in the mind is itself a thing of the mind.