7. The essence of the necessary being must contain existence; its idea must involve the idea of existence, not only logical and conceptual, but also realized.
8. We can conceive the existence of the necessary being distinct from its essence, but the reason of this is in the imperfection of the idea, which with us is not intuitive, but discursive; and consequently, we can distinguish between the logical order and the real order.
Here we find the defect of Descartes' argument by which he pretends to demonstrate the existence of God from the fact that the predicate, existence, is included in the idea of a necessary and infinite being. The idea of necessary being involves existence, but not real existence, only logical and conceptual; since after we have the idea of the necessary being, it still remains to be proved that there is an object which corresponds to this idea; the predicate belongs to the subject according to the manner in which the subject is taken, and as this is only in the purely ideal order, the predicate is also purely ideal.
9. The reality of the necessary idea cannot be demonstrated from its idea alone; but it may be demonstrated with complete evidence by introducing into the argument other elements which experience furnishes us.
Something exists; at least ourselves; at least this perception which we have in this act; at least the appearance of this act. I leave aside for the present all the questions disputed between the dogmatists and the skeptics; I only suppose a datum which no one can deny me, though he carry skepticism to the utmost exaggeration. When I say that something exists, I only mean to affirm that not every thing is a pure nothing.
If something exists, something has always existed, or there is no moment in which it could be said with truth: there is nothing. If such a moment of universal nothingness had ever been, nothing would now exist, there never could have been any thing. Let us imagine a universal and absolute nothingness; I then ask: Is it possible that any thing should come from nothing? Evidently not; therefore on the supposition of universal nothingness reality is absurd.
10. Therefore something has always existed, with a cause, without a condition on which it depends; therefore there is a necessary being. Its existence is supposed always, without relation to any hypothesis; therefore its not-being is always excluded under all conditions; therefore there exists an absolutely necessary being, that is, a being whose not-being implies a contradiction.
11. Summing up the doctrine which precedes, we may say:
I. That we have the idea of a necessary being.
II. That we deduce its existence from its idea alone.