On the one hand I have a clear and distinct idea of myself, in so far as I am a thinking, non-extended thing; and on the other hand I have a distinct idea of body, in so far a this is simply an extended, non-thinking thing. And, accordingly, it is certain that I am really distinct from my body, and exist without it.

Conquer yourself rather than the world.

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.

Science is practical philosophy.

The only thing we have power over in the universe is our own thoughts.

How can you be certain that your whole life is not a dream?

And thereby make ourselves, as it were, the lords and masters of nature.