Page 77 of 96
But whatever force we may ascribe to this principle, I am afraid 'tis too weak to support alone so vast an edifice as is that of the continued existence of all external bodies; and that we must join the constancy of their appearance to the coherence, in order to give a satisfactory account of that opinion. As the explication of this will lead me into a considerable compass of very profound reasoning, I think it proper, in order to avoid confusion, to give a short sketch or abridgment of my system, and afterwards draw out all its parts in their full compass. This inference from the constancy of our perceptions, like the precedent from their coherence, gives rise to the opinion of the continued existence of body, which is prior to that of its distinct existence, and produces that latter principle.
When we have been accustomed to observe a constancy in certain impressions, and have found that the perception of the sun or ocean, for instance, returns upon us, after an absence or annihilation, with like parts and in a like order as at its first appearance, we are not apt to regard these interrupted perceptions as different (which they really are), but on the contrary consider them as individually the same, upon account of their resemblance. But as this interruption of their existence is contrary to their perfect identity, and makes us regard the first impression as annihilated, and the second as newly created, we find ourselves somewhat at a loss, and are involved in a kind of contradiction. In order to free ourselves from this difficulty, we disguise, as much as possible, the interruption, or rather remove it entirely, by supposing that these interrupted perceptions are connected by a real existence, of which we are insensible. This supposition, or idea of continued existence, acquires a force and vivacity from the memory of these broken impressions, and from that propensity which they give us to suppose them the same; and according to the precedent reasoning, the very essence of belief consists in the force and vivacity of the conception.
In order to justify this system, there are four things requisite. First, to explain the principium individuations, or principle of identity. Secondly, give a reason why the resemblance of our broken and interrupted perceptions induces us to attribute an identity to them. Thirdly, account for that propensity, which this allusion gives, to unite these broken appearances by a continued existence. Fourthly, and lastly, explain that force and vivacity of conception which arises from the propensity.
First, as to the principle of individuation, we may observe, that the view of any one object is not sufficient to convey the idea of identity. For in that proposition, an object is the same with itself, if the idea expressed by the word object were no ways distinguished from that meant by itself; we really should mean nothing, nor would the proposition contain a predicate and a subject, which, however, are implied in this affirmation. One single object conveys the idea of unity, not that of identity.
On the other hand, a multiplicity of objects can never convey this idea, however resembling they may be supposed. The mind always pronounces the one not to be the other, and considers them as forming two, three, or any determinate number of objects, whose existences are entirely distinct and independent.
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 non-existence. 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 observed,[4] that time, in a strict sense, implies succession, and that, when we apply its idea to any unchangeable object, 'tis only by a fiction of the imagination by which[Pg 261] the unchangeable object is supposed 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 'tis by means of it that a single object, placed before us, and surveyed 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 multiplied in order to be conceived 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, through a supposed variation of time, by which the[Pg 262] mind can trace it in the different periods of its existence, without any break of the view, and without being obliged to form the idea of multiplicity or number.
I now proceed to explain the second part of my system, and show why the constancy of our perceptions makes us ascribe to them a perfect numerical identity, though 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 observed, 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 perceived, 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 conveyed to him by his senses. I shall be sure to give warning[Pg 263] when I return to a more philosophical way of speaking and thinking.
