Which is more remarkable fact about America: that millionaires are idealists or idealists become millionaires.

To go straight to the deepest depth, I went for Hegel; what unclear thoughtless flow of words I was to find there! My unlucky star led me from Hegel to Schopenhauer . . . Even in Kant there were many things that I could grasp so little that given his general acuity of mind I almost suspected that he was pulling the reader's leg or was even an imposter.

In my view all salvation for philosophy may be expected to come from Darwin's theory

It must be splendid to command millions of people in great national ventures, to lead a hundred thousand to victory in battle. But it seems to me greater still to discover fundamental truths in a very modest room with very modest means - truths that will still be foundations of human knowledge when the memory of these battles is painstakingly preserved only in the archives of the historian.

Nothing is more practical than a good theory.

The life contest is primarily a competition for available energy.

Available energy is the main object at stake in the struggle for existence and the evolution of the world.