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