By 'God', I understand, a substance which is infinite, independent, supremely intelligent, supremely powerful, and which created both myself and everything else [...] that exists. All these attributes are such that, the more carefully I concentrate on them, the less possible it seems that they could have originated from me alone. So, from what has been said it must be concluded that God necessarily exists.

Common sense is the most fairly distributed thing in the world, for each one thinks he is so well-endowed with it that even those who are hardest to satisfy in all other matters are not in the habit of desiring more of it than they already have.

Doubt is the origin of wisdom

I have concluded the evident existence of God, and that my existence depends entirely on God in all the moments of my life, that I do not think that the human spirit may know anything with greater evidence and certitude.

With me, everything turns into mathematics.

The first precept was never to accept a thing as true until I knew it as such without a single doubt.

An optimist may see a light where there is none, but why must the pessimist always run to blow it out?