Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.

The human soul is very much older than the human mind.

Just thinking that my dog loves me more than I love him, I feel shame.

A man sufficiently gifted with humor is in small danger of succumbing to flattering delusions about himself, because he cannot help perceiving what a pompous ass he would become if he did.

Natural selection does not give any preference at all to anything that, in the long run, could be advantageous for the species but blindly rewards everything that, momentarily, affords greater procreative success.

All scientific knowledge to which man owes his role as master of the world arose from playful activities.

Truth in science can be defined as the working hypothesis best suited to open the way to the next better one.