The divine command theory (DCT) of ethics holds that an act is either moral or immoral solely because God either commands us to do it or prohibits us from doing it, respectively. On DCT the only thing that makes an act morally wrong is that God prohibits doing it, and all that it means to say that torture is wrong is that God prohibits torture. DCT is wildly implausible for reasons best illustrated by the Euthyphro dilemma, which is based on a discussion of what it means for an act to be holy in Plato's Euthyphro. Substituting "moral wrongness" for "holiness" raises the dilemma: Is torture wrong because God prohibits it, or does God prohibit torture because it is already wrong?
While DCT takes the the first route, Euthyphro takes the last one: If a good God prohibits torture he does so because torture is intrinsicly wrong, not merely because he declares torture to be wrong by fiat. But if torture is intrinsicly wrong, then it is wrong regardless of whether or not God exists. Either certain acts are wrong regardless of anyone's opinions or commands (including God's), or else all that we mean by "torture is wrong" is "God prohibits torture." Rather than grounding the objectivity of ethics, DCT completely undermines it by insisting that God's commands (like those of individuals or societies) do not require justification in terms of any external principles.
DCT is thus a kind of moral relativism: what's right or wrong is what one's God (like one's self or one's society) says is right or wrong--and there are no moral standards apart from this. Yet if God said that 2+2=100, 2+2=100 would nonetheless be false because 2+2=4 is true regardless of what God says. The same point holds for moral propositions like "inflicting unnecessary suffering solely for fun is wrong." If that proposition is true, then it is true regardless of whether God commands or prohibits inflicting such suffering.
If there is no standard of "being morally right" apart from God's commands, then God could literally command us to do anything and it would be right for us to do it by definition. Whatever God commands becomes the standard of moral rightness, and there are no moral values external to God to constrain what he would or would not command. So if God commanded one person to rape another, DCT entails that that rape would be moral because "doing the right thing" is logically equivalent to "doing what God commands." A highly implausible implication is that it is impossible to even imagine God commanding a wrong act. What counts as moral or immoral behavior on DCT is completely subjective--dependent upon God's fiat--and thus arbitrary.
While some retort that goodness flows from God's nature, this merely changes the form of the dilemma: Is compassion good because it is a part of God's nature, or is compassion a part of God's nature because it is already good? The first option produces problems parallel to those for DCT. If malice were a part of God's nature, for instance, it is doubtful that malice would automatically be good. If there are any objective moral standards at all, then a god can be either good or evil, and the assessment of a god's character would depend upon appealing to standards independent of any god's commands, opinions, statements, nature, or character.
Can the Bible (or Any) God Support an Absolute Morality? (1995) by Tim Gorski, M.D.
Theists complain that the world is in moral decay because of "moral relativism," and lament that only a divine power--i.e., God--makes an absolute standard of right and wrong possible. But are "right and wrong then simply no more than this God's say-so?" Gorski asks, or "is what is right loved by this God and what is wrong hated by this God because of what right and wrong are in themselves?"
This is a review of Michael Martin's Atheism, Morality, and Meaning (Amherst, NY: Prometheus, 2002). "Michael Martin is an eminent atheist philosopher, and he gives us a hard-hitting critique of those theistic arguments which claim that all is futile in the realms of morality and meaning if there is no God. However, although Martin does well in exposing some common mistakes of theistic moral arguments, he is less convincing when he argues for objective morality in a godless world."
In Finite and Infinite Goods Adams gives his defense of a modified divine command theory its fullest elaboration, defending it against a number of standard objections. This material is essential reading for anyone interested in whether morality does or could depend on religion. Moreover, Adams thoughtfully argues for the need for several forms of moral faith, including faith that morality "is not a massive socially induced delusion." Along the way, he also offers a striking defense of liberty of conscience and church-state separation, with an emphasis on the value of critical thinking in both ethics and religion. Although Sullivan finds much to agree with here, he offers two particular criticisms of Adams's version of divine command theory. Nevertheless, Sullivan concludes that intelligent nonbelievers and believers can only benefit from carefully and critically working their way through this important book.
In Religion and Morality, Christian philosopher William J. Wainwright provides a thorough, thoughtful, and generally rigorous and fair-minded discussion of the relationship between religion and morality. He considers moral arguments for God's existence, divine command theories of morality, and possible tensions between "human morality and religious requirements," among other things. In this review Stephen Sullivan focuses his remarks on several of Wainwright's debatable claims concerning the divine command theory of ethics and the Euthyphro question, offering a few additional criticisms about Wainwright's methodology.