We call infinite that thing whose limits we have not perceived, and so by that word we do not signify what we understand about a thing, but rather what we do not understand.

I know that I exist; the question is, What is this 'I' that 'I' know.

Let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something.

The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.

I have concluded the evident existence of God, and that my existence depends entirely on God in all the moments of my life, that I do not think that the human spirit may know anything with greater evidence and certitude.

Bad books engender bad habits, but bad habits engender good books.

The entire method consists in the order and arrangement of the things to which the mind's eye must turn so that we can discover some truth.