Supernaturalism (SN) says that moral judgments describe God's will. To call something "good" means that God desires it. We are to pick our moral principles by following God's will.Ethics based on God's will
These questions are about Chapter 3 of Harry Gensler's Ethics: A Contemporary Introduction (Routledge: 1998 and 2011).
Supernaturalism holds that moral judgments describe God's will: "X is good" means "God desires X." God's will creates the moral order. Ethics is based on religion.Objections to supernaturalism
SN is defended as a Biblical teaching, as a consequence of belief in God (who is the source of all basic laws), and as the only plausible source of objectively binding duties. We can best know God's will through combining four sources: the Bible, the church, prayer, and reason.
SN, despite being initially plausible (at least to religious people), has some deep problems. SN seems to make it impossible for atheists to make positive moral judgments -- an implausible result. And Socrates's question raises further problems: "Is a good thing good because God desires it? Or does God desire it because it is good?"Arguments for supernaturalism
The arguments for SN fail if we examine them carefully. The Bible doesn't teach SN; rather, it teaches that we ought to obey God -- which might be defended on a non-SN basis. SN isn't a consequence of belief in God; basic moral principles might be like the logical truth "x=x," which is true in itself, and not true because God decided to make it true. Finally, there are ways to defend the objectivity of ethics that don't base ethics on God's will.
Some are led to SN because of they believe that ethics connects closely to religion. But it's possible to connect the two closely, even without SN.