The largest single step in the ascent of man is the change from nomad to village agriculture.

The hand is the cutting edge of the mind.

We are all shot through with enough motives to make a massacre, any day of the week that we want to give them their head.

Nations in their great ages have not been great in art or science, but in art and science.

The symbol and the metaphor are as necessary to science as to poetry.

Every animal leaves traces of what it was; man alone leaves traces of what he created.

The private motives of scientists are not the trend of science. The trend of science is made by the needs of society: navigation before the eighteenth century, manufacture thereafter; and in our age I believe the liberation of personality. Whatever the part which scientists like to act, or for that matter which painters like to dress, science shares the aims of our society just as art does.