A philosopher will not believe what he sees because he is too busy speculating about what he does not see.

Nature is never so admired as when she is understood.

A true philosopher is like an elephant; he never puts the second foot down until the first one is solidly in place.

In vain we shall penetrate more and more deeply the secrets of the structure of the human body, we shall not dupe nature; we shall die as usual.

Our sun enlightens the planets that belong to him; why may not every fixed star also have planets to which they give light?

To despise theory is to have the excessively vain pretension to do without knowing what one does, and to speak without knowing what one says.

Behold a universe so immense that I am lost in it. I no longer know where I am. I am just nothing at all. Our world is terrifying in its insignificance.