The question refers to a paper by Ernst Mayr, who was an eminent biologist on the field of the modern theory of evolution, Modern Synthesis. Mayr introduced and answered the title question in a short essay. It was published in the Proceedings of the American Philosophical Society from 1995, see Darwin's impact on modern thought, and also later as Darwin's influence.
Mayr adresses six topics where in each case Darwins theory changed the Zeitgeist. I just list the keywords, for the details of the argumentation I refer to Mayr’s paper from 1995 (9 pages):
- Against creationism: “Natural selection is the cause of order and harmony in nature. There is no need to invoke divine design.”
- Against anthropocentrism: Man is not “something entirely different from the rest of creation.” Hence it is not justified “to look at everything from his specialized viewpoint.”
- Against essentialism: The concept of essences with strict boundaries between the corresponding classes is superseded by thinking in populations, where every individual is different from each other individual.
- Against physicalism: Darwin “opposed the ideology of classical physics, as it had developed […] under the influence of Newton.”
According to Mayr Darwin instead stresses “probabilism, the importance of emergence, population thinking, quality, and importance of observation and comparison”. - Against cosmic teleology: “The modern analysis of teleology has shown that all evidence seemingly supporting cosmic teleology can be explained quite readily by natural causes.”
- Concerning free will: The Zeitgeist of Darwin’s time struggled with
the question “How could anyone be responsible for his actions if
they were dictated by his genetic makeup, his environment, by
universal laws, or, worse by God?”
Mayr ascribes to Darwin the viewpoint: “What we have, then, is a freedom of the will, a capacity of decision making which, however, is rather severly restricted by our biological constitutions, our upbringings, and prevailing circumstances.”
Assume a referee for a peer-review is comissioned by the editor of a philosophical journal: What could the referee mention as his/her summary concerning Mayr’s paper:
- Importance of the subject,
- originality of the paper,
- quality of arguments,
- possible objections,
- and eventually making a recommendation of either acceptance, requesting changes, or rejecting the paper?
Note. This question results from an exchange of ideas on this platform with @Marco Ocram. On request I can email Mayr's original paper from 1994.