| Since then both number and unity are incompatible with the relation of identity, it must lie in something that is neither of them. |
| But to tell the truth, at first sight this seems utterly impossible. |
| Betwixt unity and number there can be no medium; no more than betwixt existence and nonexistence. |
| After one object is supposed to exist, we must either suppose another also to exist; in which case we have the idea of number: Or we must suppose it not to exist; in which case the first object remains at unity. |
| To remove this difficulty, let us have recourse to the idea of time or duration. |
| I have already observd [Part II, SECT. 5.], that time, in a strict sense, implies succession, and that when we apply its idea to any unchangeable object, it is only by a fiction of the imagination, by which the unchangeable object is supposd to participate of the changes of the co-existent objects, and in particular of that of our perceptions. |
| This fiction of the imagination almost universally takes place; and it is by means of it, that a single object, placd before us, and surveyd for any time without our discovering in it any interruption or variation, is able to give us a notion of identity. |
| For when we consider any two points of this time, we may place them in different lights: We may either survey them at the very same instant; in which case they give us the idea of number, both by themselves and by the object; which must be multiplyd, in order to be conceivd at once, as existent in these two different points of time: Or on the other hand, we may trace the succession of time by a like succession of ideas, and conceiving first one moment, along with the object then existent, imagine afterwards a change in the time without any VARIATION or INTERRUPTION in the object; in which case it gives us the idea of unity. |
| Here then is an idea, which is a medium betwixt unity and. |
| number; or more properly speaking, is either of them, according to the view, in which we take it: And this idea we call that of identity. |
| We cannot, in any propriety of speech, say, that an object is the same with itself, unless we mean, that the object existent at one time is the same with itself existent at another. |
| By this means we make a difference, betwixt the idea meant by the word, OBJECT, and that meant by ITSELF, without going the length of number, and at the same time without restraining ourselves to a strict and absolute unity. |
| Thus the principle of individuation is nothing but the INVARIABLENESS and UNINTERRUPTEDNESS of any object, thro a supposd variation of time, by which the mind can trace it in the different periods of its existence, without any break of the view, and without being obligd to form the idea of multiplicity or number. |
| I now proceed to explain the SECOND part of my system, and shew why the constancy of our perceptions makes us ascribe to them a perfect numerical identity, tho there be very long intervals betwixt their appearance, and they have only one of the essential qualities of identity, VIZ, INVARIABLENESS. |
| That I may avoid all ambiguity and confusion on this head, I shall observe, that I here account for the opinions and belief of the vulgar with regard to the existence of body; and therefore must entirely conform myself to their manner of thinking and of expressing themselves. |
| Now we have already observd, that however philosophers may distinguish betwixt the objects and perceptions of the senses; which they suppose co-existent and resembling; yet this is a distinction, which is not comprehended by the generality of mankind, who as they perceive only one being, can never assent to the opinion of a double existence and representation. |
| Those very sensations, which enter by the eye or ear, are with them the true objects, nor can they readily conceive that this pen or paper, which is immediately perceivd, represents another, which is different from, but resembling it. |
| In order, therefore, to accommodate myself to their notions, I shall at first suppose; that there is only a single existence, which I shall call indifferently OBJECT or PERCEPTION, according as it shall seem best to suit my purpose, understanding by both of them what any common man means by a hat, or shoe, or stone, or any other impression, conveyd to him by his senses. |
| I shall be sure to give warning, when I return to a more philosophical way of speaking and thinking. |
| To enter, therefore, upon the question concerning the source of the error and deception with regard to identity, when we attribute it to our resembling perceptions, notwithstanding their interruption; I must here recal an observation, which I have already provd and explaind [Part II. SECT. 5.]. |
| Nothing is more apt to make us mistake one idea for another, than any relation betwixt them, which associates them together in the imagination, and makes it pass with facility from one to the other. |