Cartesian circle

The Cartesian circle is a criticism of the above that takes this form: Many commentators, both at the time that Descartes wrote and since, have argued that this involves a circular argument, as he relies upon the principle of clarity and distinctness to argue for the existence of God, and then claims that God is the guarantor of his clear and distinct ideas.

[3] The first person to raise this criticism was Marin Mersenne, in the "Second Set of Objections" to the Meditations: You are not yet certain of the existence of God, and you say that you are not certain of anything.

(AT VII 124–125)Antoine Arnauld was another one of Descartes' objectors, likewise arguing that God's existence cannot be used to prove that what one clearly and distinctly perceives is true.

[4] Descartes' own response to this criticism, in his "Author's Replies to the Fourth Set of Objections", is first to give what has become known as the Memory response;[5] he points out that in the fifth Meditation (at AT VII 69–70) he did not say that he needed God to guarantee the truth of his clear and distinct ideas, only to guarantee his memory: When I said that we can know nothing for certain until we are aware that God exists, I expressly declared that I was speaking only of knowledge of those conclusions which can be recalled when we are no longer attending to the arguments by means of which we deduced them.

[8]Another defense of Descartes against the charge of circularity is developed by Harry Frankfurt in his book Demons, Dreamers, and Madmen.