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.

I believe—and human psychologists, particularly psychoanalysts should test this—that present-day civilized man suffers from insufficient discharge of his aggressive drive. It is more than probable that the evil effects of the human aggressive drives, explained by Sigmund Freud as the results of a special death wish, simply derive from the fact that in prehistoric times intra-specific selection bred into man a measure of aggression drive for which in the social order today he finds no adequate outlet.

If you confine yourself to this Skinnerian technique, you study nothing but the learning apparatus and you leave out everything that is different in octopi, crustaceans, insects and vertebrates. In other words, you leave out everything that makes a pigeon a pigeon, a rat a rat, a man a man, and, above all, a healthy man healthy and a sick man sick.

In nature we find not only that which is expedient, but also everything which is not so inexpedient as to endanger the existence of the species.

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.

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

The neuro-physiological organization which we call instinct functions in a blindly mechanical way, particularly apparent when its function goes wrong.

This is a classical example of the process which we call, with Tinbergen, a redirected activity. It is characterized by the fact that an activity is released by one object but discharged at another, because the first one, while presenting stimuli specifically eliciting the response, simultaneously emits others which inhibit its discharge. A human example is furnished by the man who is very angry with someone and hits the table instead of the other man's jaw, because inhibition prevents him from doing so, although his pent-up anger, like the pressure within a volcano, demands outlet.

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

Visualize yourself confronted with the task of killing, one after the other, a cabbage, a fly, a fish, a lizard, a guinea pig, a cat, a dog, a monkey and a baby chimpanzee. In the unlikely case that you should experience no greater inhibitions in killing the chimpanzee than in destroying the cabbage or the fly, my advice to you is to commit suicide at your earliest possible convenience, because you are a weird monstrosity and a public danger.