"The expression of the emotions in man and animals."

"The fact that I can't remember anything from the first three years of my life is no proof that I wasn't an embryo then."

"The very existence of our senses, our reason, and our intellect, is a proof that these faculties were given us for some purpose."

"The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an agnostic."

"The world will not be inherited by the strongest, it will be inherited by those most able to change."