It would not be worth your while to reach the age of seventy if all the wisdom of the world were to be foolishness before God.

Everything factual is, in a sense, theory. The blue of the sky exhibits the basic laws of chromatics. There is no sense in looking for something behind phenomena: they are theory.

As soon as any one belongs to a narrow creed in science, every unprejudiced and true perception is gone.

Man can only endure a certain degree of unhappiness; what is beyond that either annihilates him or passes by him and leaves him apathetic

Art is long, life is short; judgement difficult, opportunity transient.

To think is easy. To act is difficult. To act as one thinks is the most difficult.

The world is for thousands a freak show; the images flicker past and vanish; the impressions remain flat and unconnected in the soul. Thus they are easily led by the opinions of others, are content to let their impressions be shuffled and rearranged and evaluated differently.