A mathematician is a blind man in a dark room looking for a black cat which isn't there.

Freedom of thought is best promoted by the gradual illumination of men’s minds which follows from the advance of science.

It strikes me that all our knowledge about the structure of our Earth is very much like what an old hen would know of the hundred-acre field in a corner of which she is scratching.

I see no good reasons why the views given in this volume should shock the religious views of anyone.

Describing laughter: The sound is produced by a deep inspiration followed by short, interrupted, spasmodic contractions of the chest, and especially the diaphragm... the mouth is open more or less widely, with the corners drawn much backwards, as well as a little upwards; and the upper lip is somewhat raised.

We will now discuss in a little more detail the Struggle for Existence.

The limit of man s knowledge in any subject possesses a high interest which is perhaps increased by its close neighbourhood to the realms of imagination.