All conditions and all circumstances in our lives are a result of a certain level of thinking. If we want to change the conditions and circumstances, we have to change the level of thinking that is responsible for it.

You imagine that I look back on my life's work with calm satisfaction. But from nearby it looks quite different. There is not a single concept of which I am convinced that it will stand firm, and I feel uncertain whether I am in general on the right track.

Energy cannot be created or destroyed, it can only be changed from one form to another.

I'm not an atheist. I don't think I can call myself a pantheist. The problem involved is too vast for our limited minds. We are in the position of a little child entering a huge library filled with books in many languages. The child knows someone must have written those books.

Marriage is but slavery made to appear civilized.

It seems to me that the idea of a personal God is an anthropological concept which I cannot take seriously. I also cannot imagine some will or goal outside the human sphere... Science has been charged with undermining morality, but the charge is unjust. A man's ethical behavior should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death.

There are two ways to live: you can live as if nothing is a miracle; you can live as if everything is a miracle.