Natural selection

Huxley was certainly not slavish in his dealings with Darwin. As shown in every biography, they had quite different and rather complementary characters. Important also, Darwin was a field naturalist, but Huxley was an anatomist, so there was a difference in their experience of nature. Lastly, Darwin's views on science were different from Huxley's views. For Darwin, natural selection was the best way to explain evolution because it explained a huge range of natural history facts and observations: it solved problems. Huxley, on the other hand, was an empiricist who trusted what he could see, and some things are not easily seen. With this in mind, one can appreciate the debate between them, Darwin writing his letters, Huxley never going quite so far as to say he thought Darwin was right.

Huxley's reservations on natural selection were of the type "until selection and breeding can be seen to give rise to varieties which are infertile with each other, natural selection cannot be proved." [60][61] Huxley's position on selection was agnostic; yet he gave no credence to any other theory.

Darwin's part in the discussion came mostly in letters, as was his wont, along the lines: "The empirical evidence you call for is both impossible in practical terms, and in any event unnecessary. It's the same as asking to see every step in the transformation (or the splitting) of one species into another. My way so many issues are clarified and problems solved; no other theory does nearly so well."