As we advance in life, we learn the limits of our abilities.

We cannot live on probabilities. The faith in which we can live bravely and die in peace must be a certainty, so far as it professes to be a faith at all, or it is nothing.

Science rests on reason and experiment, and can meet an opponent with calmness; [but] a creed is always sensitive.

There are at bottom but two possible religions--that which rises in the moral nature of man, and which takes shape in moral commandments, and that which grows out of the observation of the material energies which operate in the external universe.

To be happy is not the purpose for which you are placed in this world.

Nature is not a partisan, but out of her ample treasue house she produces children in infinite variety, of which she is equally the mother, and disowns none of them.

The best that we can do for one another is to exchange our thoughts freely; and that, after all, is about all.