81. It is the formation of ‘nominal essences’ that renders general propositions possible. ‘General certainty,’ says Locke, ‘is never to be found but in our ideas. Whenever we go to seek it elsewhere in experiment or observation without us, our knowledge goes not beyond particulars. It is the contemplation of our own abstract ideas, that alone is able to afford us general knowledge.’ (Book IV. chap. vi. sec. 16.) ‘General knowledge,’ he says again, ‘lies only in our own thoughts.’ [1] This use of ‘our ideas’ and ‘our own thoughts’ as equivalent phrases, each antithetical to ‘real existence,’ tells the old tale of a deviation from ‘the new way of ideas’ into easier paths. According to this new way in its strictness, as we have sufficiently seen, there is nowhere for anything to be found but ‘in our ideas.’ It therefore in no way distinguishes general knowledge or certainty that it cannot be found elsewhere. Locke, however, having allowed himself in the supposition that simple ideas report a real existence, other than themselves, but to which they are related as ectype to archetype, tacitly proceeds to convert them into real existences, to which ideas in general, as mere thoughts of our own, may be opposed. Along with this conversion, there supervenes upon the original distinction between simple and complex ideas, which alone does duty in the Second Book of the Essay, another distinction, essential to Locke’s doctrine of the ‘reality’ of knowledge—that between the idea, whether simple or complex, as originally given in sensation, and the same as retained or reproduced in the mind. It is only in the former form that the idea, however simple, reports, and thus (with Locke) itself is, a real existence. Such real existence is a ‘particular’ existence, and our knowledge of it a ‘particular’ knowledge. In other words, according to the only consistent doctrine that we have been able to elicit from Locke, [2] ‘it is a knowledge which consists in a consciousness, upon occasion of a present sensation—say, a sensation of redness—that some object is present here and now causing the sensation; an object which, accordingly, must be ‘particular’ or transitory as the sensation. The ‘here and now,’ as in such a case they constitute the particularity of the object of consciousness, so also render it a real existence. Separate these (‘the circumstances of time and place’ [3]) from it, and it at once loses its real existence and becomes an ‘abstract idea,’ one of ‘our own thoughts,’ of which as ‘in the mind’ agreement or disagreement with some other abstract idea can be asserted in a general proposition; e.g. ‘red is not blue.’ (Book IV. chap. vii. sec. 4.) [4]
[1] Book IV. chap. vi. sec. 13, cf. Book IV. chap. iii. sec. 31.
[2] See above, paragraph 56.
[3] Book III. chap. iii. sec. 6.
[4] In case there should be any doubt as to Locke’s meaning in this passage, it may be well to compare Book IV. chap. ix. sec. 1. There he distinctly opposes the consideration of ideas in the understanding to the knowledge of real existence. Here (Book IV. chap. vii. sec. 4) he distinctly speaks of the proposition ‘red is not blue’ as expressing a consideration of ideas in the understanding. It follows that it is not a proposition as to real existence.
An abstract idea may be a simple one.
82. It is between simple ideas, it will be noticed, that a relation is here asserted, and in this respect the proposition differs from such an one as may be formed when simple ideas have been compounded into the nominal essence of a thing, and in which some one of these may be asserted of the thing, being already included within the meaning of its name; e.g. ‘a rose has leaves.’ But as expressing a relation between ideas ‘abstract’ or ‘in the mind,’ in distinction from present sensations received from without, the two sorts of proposition, according to the doctrine of Locke’s Fourth Book, stand on the same footing.’ [1] It is a nominal essence with which both alike are concerned, and on this depends the general certainty or self-evidence, by which they are distinguished from ‘experiment or observation without us.’ These can never ‘reach with certainty farther than the bare instance’ (Book IV. chap. vi. sec. 7): i.e., though the only channels by which we can reach real existence, they can never tell more than the presence of this or that sensation as caused by an unknown thing without, or the present disagreement of such present sensations with each other. As to the recurrence of such sensations, or any permanently real relation between them, they can tell us nothing. Nothing as to their recurrence, because, though in each case they show the presence of something causing the sensations, they show nothing of the real essence upon which their recurrence depends. [2] Nothing as to any permanently real relation between them, because, although the disagreement between ideas of blue and red, and the agreement between one idea of red and another, as in the mind, is self-evident, yet as thus in the mind they are not ‘actual sensations’ at all (Book IV. chap. xi. sec. 6), nor do they convey that ‘sensitive knowledge of particular existence,’ which is the only possible knowledge of it. (Book IV. chap. iii. sec. 21.) As actual sensations and indices of reality, they do indeed differ in this or that ‘bare instance,’ but can convey no certainty that the real thing or ‘parcel of matter’ (Book III. chap. iii. sec. 18), which now causes the sensation of (and thus is) red, may not at another time cause the sensation of (and thus be) blue.’ [3]
[1] Already in Book II. (chap. xxxi. sec. 12), the simple idea, as abstract, is spoken of as a nominal essence.
[2] Cf. Book IV. chap. vi. sec. 5. ‘If we could certainly know (which is impossible) where a real essence, which we know not, is—e.g. in what parcels of matter the real essence of gold is; yet could we not be sure, that this or that quality could with truth be affirmed of gold; since it is impossible for us to know that this or that quality or idea has a necessary connexion with a real essence, of which we have no idea at all.’
Several passages, of course, can be adduced from Locke which are inconsistent with the statement in the text: e.g. Book IV. chap. iv. sec. 12. ‘To make knowledge real concerning substances, the ideas must be taken from the real existence of things. Whatever simple ideas have been found to coexist in any substance, these we may with confidence join together again, and so make abstract ideas of substances. For whatever have once had an union in nature, may be united again.’ In all such passages, however, as will appear below, the strict opposition between the real and the mental is lost sight of, the ‘nature’ or ‘substance,’ in which ideas ‘have a union,’ or are ‘found to coexist,’ being a system of relations which, according to Locke, it requires a mind to constitute, and thus itself a ‘nominal essence.’