We must learn the difficult lesson that the future of Mankind will only be tolerable when our course, in world affairs as in others, is based upon justice and law rather than the threat of naked power.

He who joyfully marches to music in rank and file has already earned my contempt. He has been given a large brain by mistake, since for him the spinal cord would fully suffice. This disgrace to civilization should be done away with at once. Heroism at command, senseless brutality, deplorable love-of-country stance, how violently I hate all this, how despicable and ignoble war is; I would rather be torn to shreds than be a part of so base an action! It is my conviction that killing under the cloak of war is nothing but an act of murder.

... it is a welcome symptom in an age which is commonly denounced as materialistic, that it makes heroes of men whose goals lie wholly in the intellectual and moral sphere.

It is not a lack of real affection that scares me away again and again from marriage. Is it a fear of the comfortable life, of nice furniture, of dishonor that I burden myself with, or even the fear of becoming a contented bourgeois.

Nobody knows how the stand of our knowledge about the atom would be without him. Personally, [Niels] Bohr is one of the amiable colleagues I have met. He utters his opinions like one perpetually groping and never like one who believes himself to be in possession of the truth.

Dear Posterity, If you have not become more just, more peaceful, and in general more sensible... then may the Devil take you!

I have only two rules which I regard as principles of conduct. The first is: Have no rules. The second is: Be independent of the opinion of others.