14. We have already said that the unity which is confounded with being, is not the unity which originates number. We here in fact encounter two different conceptions of unity, the one marking only want of distinction, and the other expressing the property of engendering number. But we are not thence to infer that the one which is identified with being is distinct from that which engenders number. All beings, one in themselves, but distinct from each other, no matter what they may be, may be conceived under the idea of number. The number three enters into the august mystery of the Trinity, and we say with all truth that in God there are three persons.
15. It is not necessary that the unity which engenders number should be real; it suffices if it be fictitious. When we take a foot measure for unity, we employ a fictitious unity, since the foot is composed of parts, but the number which results therefrom is, nevertheless, a true number.
[CHAPTER III.]
UNITY AND SIMPLICITY.
16. Real unity and simplicity are identical. What is really one has no distinction in itself; nor is it composed of parts, of which it can be said, this is not that. Evidently simplicity requires nothing more; the simple is opposed to the composite, to what is formed of many beings whereof one is not the other.
17. We meet this simplicity in none of the objects of our intuitions, excepting the acts of our own mind; so that even when we know, by discursion, that there are substances really one or simple, we do not see them in themselves.
Extension consists essentially of parts; whence it happens that we never encounter real unity or simplicity in the corporeal world as object of our sensibility. But as the composite must be resolved into the simple, as it is hard to proceed ad infinitum, we infer that the corporeal universe itself is a union of substances which, whether called points without extension, or any thing else, cannot be decomposed into others; for which reason they are really one, or simple.
18. Hence we conclude that substances may be said to be in a certain manner simple; and that things called composite are unions of substances, which in their turn form a third substance by virtue of a law presiding over them and giving them that unity which we call factitious.