What is common to all three essays is the assumption that the choice is between naturalistic ethics and moral nihilism. If so, this would be a telling criticism. But it’s not, and it’s easy to point to other moral theories that reject any attempt to identify the good with that which is natural. Here’s one, from J.S. Mill’s Three Essays on Religion: “Nature, natural, and the words derived from them … [are] one of the most copious sources of false taste, false philosophy, false morality, and even bad law.”