If I give you a pfennig, you will be one pfennig richer and I'll be one pfennig poorer. But if I give you an idea, you will have a new idea, but I shall still have it too.

The mathematician knows some things, no doubt, but not those things one usually wants to get from him.

You never fail until you stop trying.

I have not eaten enough of the tree of knowledge, though in my profession I am obligated to feed on it regularly.

My internal and external life depend so much on the work of others that I must make an extreme effort to give as much as I receive.

I advocate world government because I am convinced that there is no other possible way of eliminating the most terrible danger in which man has ever found himself. The objective of avoiding total destruction must have priority over any other objective.

The goal of pacifism is possible only though a supranational organization. To stand unconditionally for this cause is the criterion of true pacifism.