When I look at history, I am a pessimist...but when I look at prehistory, I am an optimist.

Having no human companion I felt a spirit of comradeship for the objects of nature around me. In my childish way I communed with these as with my own soul; they became the sharers of my confidence.

The intimate rapport with nature is one of the most precious things in life. Nature is indeed very close to us; sometimes closer than hands and feet, of which in truth she is but the extension. The emotional appeal of nature is tremendous, sometimes almost more than one can bear.

When in doubt, do the courageous thing.

When I look at history, I am a pessimist...but when I look at prehistory, I am an optimist.

A man is not defeated by his opponents but by himself

In spite of the great advances which have been made in our knowledge, some fundamental gaps remain. Matter, life and mind still remain utter disparate phenomena, yet the concepts of all three arise in experience; and in the human all three meet and intermingle.