If I were not a Jew I would be a Quaker.

I do not believe in the God of theology who rewards good and punishes evil. My God created laws that take care of that. His universe is not ruled by wishful thinking, but by immutable laws.

The feeling for what ought and ought not to be grows and dies like a tree, and no fertilizer of any kind will do much good. What the individual can do is give a fine example, and have the courage to firmly uphold ethical convictions in a society of cynics. I have for a long time tried to conduct myself this way, with varying success.

Highly developed spirits often encounter resistance from mediocre minds.

Gradually the conviction gained recognition that all knowledge about things is exclusively a working-over of the raw material furnished by the senses. ... Galileo and Hume first upheld this principle with full clarity and decisiveness.

Creating a new theory is not like destroying an old barn and erecting a skyscraper in its place. It is rather like climbing a mountain and gaining new and wider views.

No problem is ever solved in the same consciousness thas was used to create it.