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

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 truth about an animal is far more exciting and altogether more beautiful than all the myths woven about it.

I have found the missing link between the higher ape and civilized man; it is we.

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

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

The scientist knows very well that he is approaching ultimate truth only in an asymptotic curve and is barred from ever reaching it; but at the same time he is proudly aware of being indeed able to determine whether a statement is a nearer or a less near approach to the truth.