Reason is nothing without imagination.

The nature of matter, or body considered in general, consists not in its being something which is hard or heavy or coloured, or which affects the senses in any way, but simply in its being something which is extended in length, breadth and depth.

In the matter of a difficult question it is more likely that the truth should have been discovered by the few than by the many.

Divide each difficulty into as many parts as is feasible and necessary to resolve it.

Each problem that I solved became a rule, which served afterwards to solve other problems.

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.

A person has two passions for love and abhorrence. A big disposition to excessiveness has just a love, because it is more ardent and stronger.