Science is simply common sense at its best, that is, rigidly accurate in observation, and merciless to fallacy in logic.

Veracity is the heart of morality.

No mistake is so commonly made by clever people as that of assuming a cause to be bad because the arguments of its supporters are, to a great extent, nonsensical

Not far from the invention of fire we must rank the invention of doubt.

For myself I say deliberately, it is better to have a millstone tied round the neck and be thrown into the sea than to share the enterprises of those to whom the world has turned, and will turn, because they minister to its weaknesses and cover up the awful realities which it shudders to look at.

Friendship involves many things but, above all the power of going outside oneself and appreciating what is noble and loving in another.

The occurrence of successive forms of life upon our globe is an historical fact, which cannot be disputed; and the relation of these successive forms, as stages of evolution of the same type, is established in various cases.