Neither the true nor the false roots are always real; sometimes they are imaginary; that is, while we can always imagine as many roots for each equation as I have assigned, yet there is not always a definite quantity corresponding to each root we have imagined.

There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible.

Mathematics is a more powerful instrument of knowledge than any other that has been bequeathed to us by human agency.

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.

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

Every man is indeed bound to do what he can to promote the good of others, and a man who is of no use to anyone is strictly worthless.

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