René Descartes

I have concluded the evident existence of God, and that my existence depends entirely on Him in every moment of my life.

The principal use of prudence, of self-control, is that it teaches us to be masters of our passions, and to so control and guide them that the evils which they cause are quite bearable, and that we even derive joy from them all.

All things being equal, the simplest explanation tends to be the right one.

I shall now close my eyes, I shall stop my ears, I shall call away all my senses, I shall efface even from my thoughts all the images of corporeal things, or at least (since that is hardly possible) I shall esteem them as vain and false; and thus holding converse only with myself and considering my own nature, I shall try little by little to reach a better knowledge of and a more familiar acquaintanceship with myself.

Mathematics is a more powerful instrument of knowledge than any other that has been bequeathed to us by human agency.

The long chains of simple and easy reasonings by means of which geometers are accustomed to reach the conclusions of their most difficult demonstrations, had led me to imagine that all things, to the knowledge of which man is competent, are mutually connected in the same way.

I am sure that there is no such thing as a vacuum in nature, and that all apparent emptiness is filled with matter.