GOD the same way as the idea of a triangle includes the equality of its three angles to two right angles Consequently, it is at least as certain that God, the perfect Being in question, is or exists, as any proof in geometry can be (AT VI.36; CSMK I.129) Expanding on this in the Wfth Meditation, Descartes says that reXecting on the idea he has of God, a supremely perfect being, he clearly and distinctly perceives that everlasting existence belongs to God’s nature Existence can no more be taken away from the divine essence than the sum of the angles can be taken away from a Euclidean triangle ‘It is not less absurd to think of God (that is, a supremely perfect being) lacking existence (that is, lacking a certain perfection) than to think of a hill without a valley’ (i.e an uphill slope without a downhill slope) To see that this argument is not a simple begging of the question of God’s existence, we have to recall that Descartes believed in a Platonic world of essences independent both of the real world and the world of the mind.3 ‘When I imagine a triangle, it may be that no such Wgure exists anywhere outside my thought, or never has existed; but there certainly is its determinate nature, its essence, its form, which is unchangeable and eternal This is no Wgment of mine, and does not depend on my mind.’ Theorems can be proved about triangles whether or not anything in the world is triangular; similarly, therefore, theorems could be stated about God in abstraction whether or not there exists any such being One such theorem is that God is a totally perfect being, that is, he contains all perfections But existence itself is a perfection; hence, God, who contains all perfections, must exist The vulnerable point in the argument is the claim that existence is a perfection This was siezed upon by Pierre Gassendi, author of the Wfth set of Objections to the Meditations ‘Neither in God nor in anything else is existence a perfection, but rather that without which there are no perfections Existence cannot be said to exist in a thing like a perfection; and if a thing lacks existence, then it is not just imperfect or lacking perfection, it is nothing at all.’ Descartes had no ultimately convincing answer to this objection, and it was later to be pressed home conclusively by Immanuel Kant and Gottlob Frege.4 See p 185 above See below, p 325 307