The further the spiritual evolution of mankind advances, the more certain it seems to me that the path to genuine religiosity does not lie through the fear of life, and the fear of death, and blind faith, but through striving after rational knowledge.

Never memorize something that you can look up.

Anyone who thinks science is trying to make human life easier or more pleasant is utterly mistaken.

Insofar as we may at all claim that slavery has been abolished today, we owe its abolition to the practical consequences of science

I love to travel, but hate to arrive.

Berlin is the place to which I am most closely bound by human and scientific ties.

I do not at all believe in human freedom in the philosophical sense... Schopenhauer’s saying, ‘A man can do what he wants, but not will what he wants,’ has been a very real inspiration to me since my youth; it has been a continual consolation in the face of life’s hardships, my own and others’, and an unfailing wellspring of tolerance. This realization mercifully mitigates the easily paralyzing sense of responsibility and prevents us from taking ourselves and other people too seriously; it is conducive to a view of life which, in part, gives humour its due.