Descartes constructed as noble a road of science, from the point at which he found geometry to that to which he carried it, as Newton himself did after him. ... He carried this spirit of geometry and invention into optics, which under him became a completely new art.

Life is thickly sown with thorns. I know no other remedy than to pass rapidly over them. The longer we dwell on our misfortunes the greater is their power to harm us.

When a man is in love, jealous, and just whipped by the Inquisition, he is no longer himself.

Let each of us boldly and honestly say: How little it is that I really know!

The only way to compel men to speak good of us is to do it.

All men are by nature free; you have therefore an undoubted liberty to depart whenever you please, but will have many and great difficulties to encounter in passing the frontiers.

Doubt is uncomfortable, certainty is ridiculous.