Geometry is not true, it is advantageous.

All great progress takes place when two sciences come together, and when their resemblance proclaims itself, despite the apparent disparity of their substance.

Pure logic could never lead us to anything but tautologies; it can create nothing new; not from it alone can any science issue.

Experiment is the sole source of truth. It alone can teach us something new; it alone can give us certainty.

Hypotheses are what we lack the least.

Why is it that showers and even storms seem to come by chance, so that many people think it quite natural to pray for rain or fine weather, though they would consider it ridiculous to ask for an eclipse by prayer.

What is it indeed that gives us the feeling of elegance in a solution, in a demonstration?