I never allow myself to become discouraged under any circumstances. The three great essentials to achieve anything worthwhile are first, hard work, second, stick-to-ittiveness, third, common sense.

If God has created the world, his primary worry was certainly not to make its understanding easy for us

When the solution is simple, God is answering.

Politics is far more complicated than physics.

There are two different conceptions about the nature of the universe: (1) the world as a unity dependent on humanity; (2) the world as a reality independent of the human factor.

If you want to know the future, look at the past.

I believe that the first step in the setting of a real external world is the formation of the concept of bodily objects and of bodily objects of various kinds.