Divine Command Theory
Fundamental principle: What makes an act right is the fact that God commands it.
Note that you can believe in the existence of God, and believe we should do what God commands us to do, but still reject Divine Command as a justification for fundamental moral principles. Believing that we ought to do what God commands does not commit you to believing that this command is what makes right actions right.
- How do we know what God commands or forbids? How do we distinguish true prophets from insane people? If someone claims to hear God command mass murder, we use our prior set of moral standards to determine that it's not a true revelation (God would never command anyone to do something so awful). But in that case we use our moral values to judge the truth of revelation, not vice versa as Divine Command requires. This implies that there are independent moral standards.
Is it right because God commands it, or does God command it because it's right?
If it's right because God commands it, then right is arbitrary and could change at any time. In that case, there's nothing inherently wrong with murder; God just happens to forbid it. But we tend to think that there must be a reason why murder is wrong.
But if God commands it because it's right, or forbids it because it's wrong, then there must be a prior standard of right and wrong that applies to God, in which case we can disregard Divine Command as a justification.
There are laws of nature, which animals and inanimate objects are forced to obey, and we should regard them as supreme and the basis for our laws. Everything has a proper function in nature's order, and the proper (right) way for people to live is according to that order. Example: male dominance is good because we find it everywhere in nature.
Sometimes "natural law" is a form of divine command theory. The universe is created by a supreme being, and we should obey its will. But because its will is not transparent (we can't just read commands out of the Bible), we have to study nature and its laws to determine how we should live.
- It confuses two meanings of "law", only one of which is moral. One kind of law is intended to govern the behavior of beings who can choose between right and wrong (these are the laws we give ourselves). The other kind of law is simply an observed regularity in the physical world: the law of gravity, or the rate of acceleration of falling objects. Just because we use the same word for both doesn't mean that there's any moral significance in the latter kind of law ("laws of nature").
There are all kinds of common animal behaviors that we don't consider appropriate for humans, like marking territory with urine.
There are inconsistent patterns of behavior among animals, but the theory gives us no way to tell whom to emulate: should we be like sheep, or like wolves? Does nature tell us to live in a strict hierarchy, like bees, or in an egalitarian collective, like prairie dogs? Should we cooperate, like ants, or compete, like tigers?