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

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

“The most ordinary things are to philosophy a source of insoluble puzzles. With infinite ingenuity it constructs a concept of space or time and then finds it absolutely impossible that there be objects in this space or that processes occur during this time.... the source of this kind of logic lies in excessive confidence in the so-called laws of thought.”

“Philosophy gets on my nerves. If we analyze the ultimate ground of everything, then everything finally falls into nothingness. But I have decided to resume my lectures again and look the Hydra of doubt straight into the eye, and it be quite ominous if one values one's life.”

“O! immodest mortal! Your destiny is the joy of watching the evershifting battle!”

“Who sees the future? Let us have free scope for all directions of research; away with dogmatism, either atomistic or anti-atomistic!”

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