If morality is just whatever God commands, then morality is arbitrary — God could have commanded torture for fun and it would have been obligatory, which shows divine command theory makes ethics groundless.

Why people find it persuasive

This is the Euthyphro dilemma in modern dress: either God commands things because they're good (so goodness is independent of God) or things are good because God commands them (so goodness is just divine whim). Neither horn looks friendly to theism.

Important distinctions

• • Divine command theory of moral obligation vs. divine nature theory of moral goodness.
• • Arbitrary in the sense of 'could have been otherwise for no reason' vs. grounded in a necessarily good nature that could not have been otherwise.
• • Commands as the source of obligation vs. commands as the mode by which an independently good God communicates obligation.
• • Logical possibility of God commanding evil vs. metaphysical possibility given a necessarily good nature.

Christian response

• • Most sophisticated theists reject a bare 'goodness is whatever God happens to command' view and instead hold that God's commands express his necessarily good, unchanging nature. On this modified divine command theory, moral obligations are grounded in commands, but the commands themselves are not arbitrary because they flow from a nature that is essentially loving, just, and wise — not from an unconstrained will that could have gone any which way.
• • This dissolves the dilemma rather than merely picking a horn: goodness is not independent of God (avoiding the first horn, which threatens divine sovereignty and simplicity) and commands are not arbitrary stipulations severed from goodness (avoiding the second horn), because God's nature just is the standard of goodness, and his commands are necessarily consistent expression of that nature, not free-floating decrees.
• • The claim 'God could have commanded torture for fun' equivocates on 'could.' It is true in a thin, merely logical sense that we can conceive a sentence describing God commanding cruelty, but if God is essentially good, it is not metaphysically possible for him to do so, any more than it is possible for a triangle to have four sides even though we can form the words. Modal claims about what a necessarily good being 'could' do are governed by that being's nature, not by unconstrained combinatorics.
• • This view also explains why morality feels both objective (rooted in an unchanging nature, not human convention) and genuinely obligatory (commanded by a personal authority with rightful claim on us, not merely descriptive of abstract Platonic forms that exert no obvious motivational pull). It captures the strengths of both horns of Euthyphro while avoiding their weaknesses.
• • A remaining task for the theist is to give independent, non-circular content to 'good' as applied to God's nature, so the theory is not covertly definitional. Many do this by appeal to properties like maximal love, justice, and rationality that are independently intelligible to us through moral experience and reason, and then identify God as the being who perfectly instantiates and grounds those properties.

Christian counterresponse

The theist can respond that necessary beings do not require external justification for their nature in the way contingent choices do — asking 'why is God's nature the standard' may be like asking why the actual world's basic logical laws are the ones that hold, a place where explanation plausibly bottoms out. On the historical worry, the theory constrains rather than licenses anything-goes readings: it requires that hard texts be interrogated against a nature independently characterized by love and justice, not simply used as evidence for whatever occurred.