LEIBNITZ.¹

"Although I am for innate ideas, and in particular for that of God, I do not think that the demonstrations of the Cartesians drawn from the idea of God are perfect. I have shown fully elsewhere (in the Actes de Leipsic, and in the Memoires de Trevoux) that what Descartes has borrowed from Anselm, Archbishop of Canterbury, is very beautiful and really very ingenious, but that there is still a gap therein to be filled. This celebrated archbishop, who was without doubt one of the most able men of his time, congratulates himself, not without reason, for having discovered a means of proving the existence of God a priori, by means of its own notion, without recurring to its effects. And this is very nearly the force of his argument: God is the greatest or (as Descartes says) the most perfect of beings, or rather a being of supreme grandeur and perfection, including all degrees thereof. That is the notion of God. See now how existence follows from this notion. To exist is something more than not to exist, or rather, existence adds a degree to grandeur and perfection, and as Descartes states it, existence is itself a perfection. Therefore this degree of grandeur and perfection, or rather this perfection which consists in existence, is in this supreme all­great, all­perfect being: for otherwise some degree would be wanting to it, contrary to its definition. Consequently this supreme being exists. The Scholastics, not excepting even their Doctor Angelicus, have misunderstood this argument, and have taken it as a paralogism; in which respect they were altogether wrong, and Descartes, who studied quite a long time the scholastic philosophy at the Jesuit College of La Fleche, had great reason for re­establishing it. It is not a paralogism, but it is an imperfect demonstration, which assumes something that must still be proved in order to render it mathematically evident; that is, it is tacitly assumed that this idea of the all­great or all­perfect being is possible, and implies no contradiction. And it is already something that by this remark it is proved that, assuming that God is Possible, he exists, which is the privilege of divinity alone. We have the right to presume the possibility of every being, and especially that of God, until some one proves the contrary. So that this metaphysical argument already gives a morally demonstrative conclusion, which declares that according to the present state of our knowledge we must judge that God exists, and act in conformity thereto. But it is to be desired, nevertheless, that clever men achieve the demonstration with the strictness of a mathematical proof, and I think I have elsewhere said something that may serve this end."

¹ New Essays Concerning Human Understanding. Translated by A.G. Langley. New York, 1896. P. 502 at seq.