The competition between human beings destroys with cold and diabolic brutality... Under the pressure of this competitive fury we have not only forgotten what is useful to humanity as a whole, but even that which is good and advantageous to the individual. [...] One asks, which is more damaging to modern humanity: the thirst for money or consuming haste... in either case, fear plays a very important role: the fear of being overtaken by one's competitors, the fear of becoming poor, the fear of making wrong decisions or the fear of not being up to snuff...

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

More than any other product of human scientific culture scientific knowledge is the collective property of all mankind.

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.

Barking dogs may occasionally bite, but laughing men hardly ever shoot!

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.

...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.