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

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

Sensations are nothing but confused modes of thinking.

Your joy is your sorrow unmasked. And the self-same well from which your laughter rises was often-times filled with your tears.

There is a little gland in the brain in which the soul exercises its functions in a more particular way than in the other parts.

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.

How do we know that anything really exists, that anything is really the way it seems ot us through our senses?