We had better dispense with the personification of evil, because it leads, all too easily, to the most dangerous kind of war: religious war.

I believe that present day civilized man suffers from insufficient discharge of his aggressive drive

...he who has seen the intimate beauty of nature cannot tear himself away from it again. He must become either a poet or a naturalist and, if his eyes are keen and his powers of observation sharp enough, he may well become both.

Man appears to be the missing link between anthropoid apes and human beings.

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

The fidelity of a dog is a precious gift.

The distance at which all shooting weapons take effect screens the killer against the stimulus sensation which would otherwise activate his killing inhibitions. The deep, emotional layers of our personality simply do not register the fact that the crooking of the finger to release a shot tears the entrails of another man.