I have become rather like King Midas, except that everything turns not into gold but into a circus.

One can't teach a cat not to catch birds

A man has to work so hard so that something of his personality stays alive. A tomcat has it so easy, he has only to spray and his presence is there for years on rainy days.

My interest in science was always essentially limited to the study of principles.... That I have published so little is due to this same circumstance, as the great need to grasp principles has caused me to spend most of my time on fruitless pursuits.

Overpopulation in various countries has become a serious threat to the health of people and a grave obstacle to any attempt to organise peace on this planet

Imagination is greater than knowledge.

No worthy problem is ever solved within the plane of its original conception.