Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer.

Experience never misleads; what you are misled by is only your judgment, and this misleads you by anticipating results from experience of a kind that is not produced by your experiments.

To lie is vile, to tell truth is excellent, if not noble.

A bird is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements, but not with a corresponding degree of strength, though it is deficient only in the power of maintaining equilibrium. We may therefore say that such an instrument constructed by man is lacking in nothing except the life of the bird, and this life must needs be supplied from that of man.

The most beautiful words of love are told in silence for a look.

There is no higher or lower knowledge, but one only, flowing out of experimentation.

I roamed the countryside searching for answers to things I did not understand. Why shells existed on the tops of mountains. How the various circles of water form around the spot which has been struck by a stone, and why a bird sustains itself in the air.