Born 1596 at Sos, Silhon was secretary to Cardinal Richelieu (1585–1642) and was appointed by him in 1634 to l‘Académie française, established by Louis XIII the following year. He served for many years as a state councilor and was also secretary to Richelieu's successor as chief minister, Cardinal Mazarin (1602–61). He died in Paris, February 1667. Silhon was a close friend of Descartes, though little, if any, of their correspondence has survived (see Descartes’ letters at AT I 352–54, CSMK 55–56; AT V 134–39, CSMK 330–32, which may have been to Silhon). His two most important works are Les deux vérités (1626) and L'immortalité de l’âme (1634). The former begins with arguments against skepticism, for according to Silhon it is only once skepticism has been refuted that reason can be reliably employed to prove God's existence (the first truth), which is itself necessary for the proof that the soul is immortal (the second truth) (see doubt and soul, immortality of). The latter is of interest for Silhon's argument, directed against the skeptics of his day, that even though a man's senses may deceive him, and even though he cannot know with certainty whether he is asleep or awake, nonetheless, when he judges that he exists, he cannot at that moment be mistaken. Thus, there is something he knows to be true (cf. AT VI 31–32, CSM I 127). However, unlike Descartes, for whom the cogito is not the result of a deduction but stands on its own as a clear and immediate intuition (see AT VI 32, CSM I 127; AT VII 140, CSM II 100), Silhon argues that the certainty attained by his argument rests upon the prior truth that whatever acts must have being. By making “I exist” the conclusion of a deduction, he leaves the door open to the skeptic to doubt the premise from which it is said to follow. Descartes mentions no debt to Silhon for his own cogito argument, nor does Silhon claim any priority in the matter.

See also Certainty, Clarity and Distinctness, Cogito Ergo Sum, Deduction, Mind, Reason, Truth