Even people who aren’t geniuses can outthink the rest of mankind if they develop certain thinking habits.

...I believe there exists, & I feel within me, an instinct for the truth, or knowledge or discovery, of something of the same nature as the instinct of virtue, & that our having such an instinct is reason enough for scientific researches without any practical results ever ensuing from them.

I would give absolutely nothing for the theory of Natural Selection, if it requires miraculous additions at any one stage of descent.

Nevertheless so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!

I was a young man with uninformed ideas. I threw out queries, suggestions, wondering all the time over everything; and to my astonishment the ideas took like wildfire. People made a religion of them.

Our faculties are more fitted to recognize the wonderful structure of a beetle than a Universe.

On the theory of natural selection we can clearly understand the full meaning of that old canon in natural history, “Natura non facit saltum.” This canon, if we look only to the present inhabitants of the world, is not strictly correct, but if we include all those of past times, it must by my theory be strictly true.