Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of facts will certainly reject my theory.

Everything in nature is the result of fixed laws.

The main conclusion here arrived at ... is that man is descended from some less highly organized form.

It is no valid objection that science as yet throws no light on the far higher problem of the essence or origin of life. Who can explain gravity? No one now objects to following out the results consequent on this unknown element of attraction.

I have no great quickness of apprehension or wit which is so remarkable in some clever men, for instance Huxley

It is not the most intellectual of the species that survives; it is not the strongest that survives; but the species that survives is the one that is able best to adapt and adjust to the changing environment in which it finds itself.

Only the fittest will survive.