in his idea, are of such a special character, so far in excess of any other possible cause, that the only thing adequate to produce an idea of that would be the thing itself, God.” Then there is the problem of how it can be possible for a finite mind to have a clear and distinct idea of an infinite God. Descartes was challenged on this and in the first set of Replies says, “the infinite, qua infinite, can in no way be grasped. But it can still be understood, in so far as we can clearly and distinctly understand that something is such that no limitations can be found in it, and this amounts to understanding clearly that it is infinite.” Cottingham argues that making this distinction is “an unsatisfactory line of defence” He refers to Descartes own analogy of a man who had an idea of a very complex machine from which it could be inferred that he had either seen the machine, been told about the machine or was clever enough to invent it. He adds, “But clearly such inferences will hold only if the man has a quite determinate idea of the machine. If a man comes up and says that he has an idea of a marvellous machine which will feed the hungry by making proteins out of sand, I shall be impressed neither by his experience nor by his powers of invention if it turns out that that is all there is to the idea, and he has no conception, or only the haziest conception, of how such a machine might work.” Finally, it might be added, for this proof to do the work Descartes is asking of it the proof needs to be clear and distinct. Given the above considerations this is unconvincing. In the second set of replies Descartes says this is the fault of the reader: See also Cartesian Circle References Sources René Descartes, Meditations and Other Metaphysical Writings Christopher Hamilton (2003), Understanding Philosophy Arguments for the existence of God René Descartes