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

Most people have forgotten how to live with living creatures, with living systems and that, in turn, is the reason why man, whenever he comes into contact with nature, threatens to kill the natural system in which and from which he live.

Scientific truth is universal, because it is only discovered by the human brain and not made by it, as art is.

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

Most of the vices and mortal sins condemned today correspond to inclinations that were purely adaptive or at least harmless in primitive man

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