An intimate friend and a hated enemy have always been indispensable requirements for my emotional life; I have always been able to create them anew, and not infrequently my childish ideal has been so closely approached that friend and enemy coincided in the same person.

Love can not be much younger than the lust for murder.

Look into the depths of your own soul and learn first to know yourself, then you will understand why this illness was bound to come upon you and perhaps you will thenceforth avoid falling ill.

The time comes when each of us has to give up as illusions the expectations which, in his youth, he pinned upon his fellow-men, and when he may learn how much difficulty and pain has been added to his life by their ill-will.

It is a mistake to believe that science consists in nothing but conclusively proved propositions, and it is unjust to demand that it should. It is a demand made by those who feel a craving for authority in some form to replace the religious catechism by something else, even a scientific one.

The very emphasis of the commandment: Thou shalt not kill, makes it certain that we are descended from an endlessly long chain of generations of murderers, whose love of murder was in their blood as it is perhaps also in ours.

Life, as we find it, is too hard for us; it brings us too many pains, disappointments and impossible tasks. In order to bear it we cannot dispense with palliative measures... There are perhaps three such measures: powerful deflections, which cause us to make light of our misery; substitutive satisfactions, which diminish it; and intoxicating substances, which make us insensible to it.