Thus each truth discovered was a rule available in the discovery of subsequent ones.

I was convinced that our beliefs are based much more on custom and example than on any certain knowledge.

I am thing that thinks: that is, a things that doubts,affirms, denies, understands a few things, is ignorant of many things, is willing, is unwilling, and also which imagines and has sensory perceptions.

When I consider this carefully, I find not a single property which with certainty separates the waking state from the dream. How can you be certain that your whole life is not a dream?

I can doubt everything, except one thing, and that is the very fact that I doubt. Simply put - I think, therefore I am

For I found myself embarrassed with so many doubts and errors that it seemed to me that the effort to instruct myself had no effect other than th eincreasing discovery of my own ignorance

The principal effect of the passions is that they incite and persuade the mind to will the events for which they prepared the body.