Those who have never known the deep intimacy and the intense companionship of happy mutual love have missed the best thing that life has to give.

I hold all knowledge that is concerned with things that actually exist - all that is commonly called Science - to be of very slight value compared to the knowledge which, like philosophy and mathematics, is concerned with ideal and eternal objects, and is freed from this miserable world which God has made.

There are two motives for reading a book; one, that you enjoy it; the other, that you can boast about it.

Who ever heard a theologian preface his creed, or a politician conclude his speech with an estimate of the probable error of his opinion?

Not to be absolutely certain is, I think, one of the essential things in rationality.

You find as you look around the world that every single bit of progress in humane feeling, every improvement in the criminal law, every step toward the diminution of war, every step toward better treatment of the colored races, or every mitigation of slavery, every moral progress that there has been in the world, has been consistently opposed by the organized churches of the world. I say quite deliberately that the christian religion, as organized in its churches, has been and still is the principle enemy of moral progress in the world.

Science seems to be at war with itself.... Naive realism leads to physics, and physics, if true, shows naive realism to be false. Therefore naive realism, if true, is false; therefore it is false.