The method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind.

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.

The man of science has learned to believe in justification, not by faith, but by verification.

Nothing great in science has ever been done by men, whatever their powers, in whom the divine afflatus of the truth-seeker was wanting.

Education is the instruction of the intellect in the laws of Nature.

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

To a clear eye the smallest fact is a window through which the infinite may be seen.