Either there are no corporeal substances, and bodies are merely phenomena which are true or consistent with each other, such as a rainbow or a perfectly coherent dream, or there is in all corporeal substances something analogous to the soul.

He who understands Archimedes and Apollonius will admire less the achievements of the foremost men of later times.

The greatness of a life can only be estimated by the multitude of its actions. We should not count the years, it is our actions which constitute our life.

Music is a secret and unconscious mathematical problem of the soul.

There is nothing without reason.

But it is the knowledge of necessary and eternal truths which distinguishes us from mere animals, and gives us reason and the sciences, raising us to knowledge of ourselves and God. It is this in us which we call the rational soul or mind.

I hold that it is only when we can prove everything we assert that we understand perfectly the thing under consideration.