Extinguished theologians lie about the cradle of every science, as strangled snakes beside that of Hercules

Living things have no inertia, and tend to no equilibrium.

Deduction, which takes us from the general proposition to facts again-teaches us, if I may so say, to anticipate from the ticket what is inside the bundle.

History warns us that it is the customary fate of new truths to begin as heresies and to end as superstitions.

Agnosticism, in fact, is not a creed, but a method, the essence of which lies in the rigorous application of a single principle. ... Positively the principle may be expressed: In matters of the intellect, follow your reason as far as it will take you, without regard to any other consideration. And negatively: In matters of the intellect, do not pretend that conclusions are certain which are not demonstrated or demonstrable.

The only question which any wise man can ask himself, and which any honest man will ask himself, is whether a doctrine is true or false.

The whole analogy of natural operations furnishes so complete and crushing an argument against the intervention of any but what are termed secondary causes, in the production of all the phenomena of the universe; that, in view of the intimate relations between Man and the rest of the living world; and between the forces exerted by the latter and all other forces, I can see no excuse for doubting that all are co-ordinated terms of Nature's great progression, from the formless to the formed from the inorganic to the organic from blind force to conscious intellect and will.