Great men are they who see that spiritual is stronger than any material force, that thought rules the world.

The kingdoms and the crowns which the Moslems have lost in the course of history are far less important than the kingdom of the free and searching mind which they have lost in the process of intellectual stagnation.

The highest possible stage in moral culture is when we recognize that we ought to control our thoughts.

I think, therefore I am.

What is the hardest task in the world? To think.

Thinking is the endeavor to capture reality by means of ideas.

By space the universe encompasses and swallows me up like an atom; by thought I comprehend the world.

Man is but a reed, the feeblest thing in nature; but he is a thinking reed.

Those who think are excessively few; and those few do not set themselves to disturb the world.

The essence of thought, as the essence of life, is growth.