The a priori principle that God would never deceive us is not itself a secure foundation against skepticism

Crathorn endeavored elsewhere to gather at least a few certitudes, since one could doubt whether the a priori principle that God would never deceive us is itself certain. To rebut the skeptic, he turns back to Augustine’s version of the cogito-argument to prove that we can at least be certain of our own mental activity, for if one were to doubt a proposition such as ‘I am’, it would follow that he exists, since he who does not exist does not doubt. Hence, no one can be in doubt concerning the pr