The reproaches against science for not having yet solved the problems of the universe are exaggerated in an unjust and malicious manner; it has truly not had time enough yet for these great achievements. Science is very young--a human activity which developed late.

Our possibilities of happiness are already restricted by our constitution. Unhappiness is much less difficult to experience. We are threatened with suffering from three directions: from our own body, which is doomed to decay and dissolution and which cannot even do without pain and anxiety as warning signals; from the external world, which may rage against us with overwhelming and merciless forces of destruction; and finally from our relations to other men. The suffering which comes from this last source is perhaps more painful to us than any other.

Unexpressed emotions will never die. They are buried alive and will come forth later in uglier ways.

A strong egoism is a protection against disease, but in the last resort we must begin to love in order that we may not fall ill, and must fall ill if, in consequence of frustration, we cannot love.

The voice of the intellect is soft one, but it does not rest until it has gained a hearing. Ultimately, after endless rebuffs, it succeeds. This is one of the few points in which one may be optimistic about the future of mankind.

Only a good-for-nothing is not interested in his past.

By abolishing private property one deprives the human love of aggression.