Ontological Argument
Leibniz (Gottfried)
Source: Leibniz, Remnant, Bennett - New Essays on Human Understanding
Paper - Abstract

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Plantinga’s Comments

  1. Leibniz considered the Cartesian form of the argument to be valid, but incomplete, inasmuch as it presupposed the possibility of that which it purported to prove. If the supreme being, as conceived by Descartes, should be one that could not exist in reality, then no purely formal proof could establish its necessary existence.
  2. Leibniz, accordingly, proposed to show first that it is possible for such a being to exist, given which it follows, from the ontological argument, that God does exist.
Extract from the Full Text1
    Although I am for innate ideas, and in particular for that of God, I do not think that the demonstration 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 all-great, all-perfect 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 re-establishing 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 all-great or all-perfect 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 someone 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.

Plantinga’s Comments
    Here2. Leibniz proposes to demonstrate that the idea of God is a logically consistent idea, i.e., that God is possible.

That The Most Perfect Being Exists
  1. I call every simple quality which is positive and absolute, or expresses whatever it expresses without any limits, a perfection.
  2. But a quality of this sort, because it is simple, is therefore irresolvable or indefinable, for otherwise, either it will not be a simple quality but an aggregate of many, or, if it is one, it will be circumscribed by limits and so be known through negations of further progress contrary to the hypothesis, for a purely positive quality was assumed.
  3. From these considerations it is not difficult to show that all perfections are compatible with each other or can exist in the same subject.
  4. For let the proposition be of this kind:
      A and B are incompatible
    (for understanding by A and B two simple forms of this kind or perfections, and it is the same if more are assumed like them), it is evident that it cannot be demonstrated without the resolution of the terms A and B, of each or both; for otherwise their nature would not enter into the ratiocination and the incompatibility could be demonstrated as well from any others as from themselves. But now (by hypothesis) they are irresolvable. Therefore this proposition cannot be demonstrated from these forms.
  5. But it might certainly be demonstrated by these if it were true, because it is not true per se, for all propositions necessarily true are either demonstrable or known per se. Therefore, this proposition is not necessarily true.
  6. It is granted, therefore, that either a subject of all perfections or the most perfect being can be known.
  7. Whence it is evident that it also exists, since existence is contained in the number of the perfections.
  8. I showed this reasoning to D. Spinoza when I was in The Hague, who thought it solid; for when at first he opposed it, I put it in writing and read this paper before him.


In-Page Footnotes

Footnote 1: Footnote 2:

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