Divine command theory

Divine command theory suggests that any statement about ethics is actually a statement about the attitudes and desires of God. That is, it claims that God's commands and morality are identical. To suggest that morality can exist without God is therefore a contradiction.

Begging the question
Divine command theory cannot prove that God is the source of morality because that is precisely what it assumes. That is, divine command theory assumes that whatever God commands must be moral (in fact, in most cases it defines morality that way). However, it's not clear that I am morally required to do something just because God commands it. I might want to obey God in order to escape punishment, but this is a matter of my own selfish interest and not an objective moral obligation. Similarly, it's not clear why I should assume that there's no other possible source of morality.

Unless divine command theory can first demonstrate that it is the most appropriate view of ethics, one cannot assume that it is correct to prove anything else.

Non-standard usage of the words "good" or "moral"
Most people have an intuitive sense of what it means for an action to be good or to have a moral obligation, and this set of moral attitudes typically pre-dates or is independent of any religious beliefs. To define a new meaning for "morality" as meaning what God wants, then to act as if this is the same as the everyday conception of morality, is to commit an equivocation fallacy. Morality is either a system for determining which actions are right or wrong, or a desire to obey the will of God. It can't mean both things at the same time, unless one first demonstrates that both meanings are equivalent.

Divine command theory is not an objective system of morals

 * See also:Euthyphro dilemma

Divine command theory implies that whatever God commands must be the morally correct course of action. Therefore, if/when God endorses genocide, infanticide, animal sacrifice, slavery, or rape, those things are good, whereas if/when he forbids eating certain foods or working on certain days or having certain kinds of kinky sex, those things immediately become bad. This makes divine command theory a subjective theory of morals, one which is arbitrary and can change at God's whim.

One way of countering this argument is to say "God wouldn't do that", but this doesn't help at all. For one, in many religious traditions he does do such things. For another, if God is the source of morality, he can do whatever he wants and it would still be just as "good" as anything else.

Thomas Aquinas believed that God's commands come from his own (unchanging?) essence and thus were not arbitrary pronouncements. This is irrelevant to the problem. Either there is a single objective, necessary code of morals that governs everything, in which case God's commands merely reflect (or fail to reflect) this standard, or else there is no such code, and so the commandments of God cannot reflect an objective morality. Either way, it gets you nowhere to say that actions are good for no other reason than because God approves of them.

Divine command theory is impractical

 * See also:Which god?

Whether divine command theory is true or not (and there seems to be no reason to think that it is), it is often not an effective method of settling moral dilemmas. For one, it's not clear which religious tradition is correct. For another, religious texts tend to contain many conflicting, arbitrary, or excessively specific rules. These rules rarely allow a clear method of generalizing these ideas to every possible situation, so a believer is forced to do much the same thing that an atheist does, which is to work out moral principles and ideas for herself. Often, the fact that the believer is bound to respect certain statements as absolute truth makes this process even harder, because those statements may not make good sense, or may make sense in most situations but be absurd in others. Divine command theory thus fails to provide moral guidance for much the same reason that religions often fail to provide moral guidance.