Taken from Larrys Text -- please wikify and make conform to NPOV:
The second, then, is the argument from morality. Here goes. It is God, God alone, who decides what is right and wrong. God's commands are the only and ultimate standard of morality. So, if one supposes that God does not exist, then one is doomed to a life without moral standards. One will have no reasons to think that lying, stealing, or even murder are wrong. That means that, as a nonbeliever, one contributes to the corruption of oneself, others, and the entire culture. According to the famous catchphrase, "If God is dead, then everything is permitted." In other words, if we no longer believe that God exists, then we will think we are morally permitted to do anything; and that will corrupt us. To avoid such moral corruption, and to have stable standards of morality, we must believe that God exists. Therefore, God exists.
Now there is one important premise that this argument rests on -- namely, that God's commands are the only possible standard of morality. This implies a theory of ethics, which is called theological ethics, or alternatively, the divine command theory. According to theological ethics, something is right just in case God commands it; something is wrong just in case God forbids it; and something is morally permissible just in case God neither commands nor forbids it.
I am going to present one common objection to theological ethics. I'm stealing this objection from Socrates, who first came up with it. Namely this: do we want to say that an action is right because God commands it, or do we want to say, instead, than God commands an action because it is right? Look, if we say that actions are right because God commands them, then we can't explain why God commands what he does. On the other hand, if we say that God commands right actions because they are right, then we?re saying that what makes actions right isn't just the fact that God commands them. Rather, God sees that an action is right, and commands us to do it because it is right. If we accept theological ethics as our only ethical theory, then there's no moral explanation for why God commands what he does. If God had commanded us to murder each other, then that would be right -- by definition.
You might object to that, and say that of course God wouldn't command us to murder each other. That's just ridiculous, you'll say. But why is it ridiculous? If you say, "Because God commanded us to love each other, not murder each other," you?re arguing in a circle. You?re saying that God commanded us not to murder -- why? -- because God commanded us not to murder. Or else, if you?re not arguing in a circle like this, then you?re saying there just is no reason why God commands what he does.
My proposal is that there is something about human nature, about human happiness, and about the universe we live in that makes murder wrong; God recognizes these facts and, having recognized them, commands us not to murder each other. Now if you disagree, and if you accept theological ethics, then look at what you?re saying: you?re saying, "There is nothing about human nature, nothing about human happiness, nothing about the universe that explains, or accounts for, why murder is wrong. Or rather, the only thing that explains why murder is wrong is that God forbids it; and there's no reason for him to forbid it, nothing about us or our world." I am hoping you can see that that is a very implausible view.
So what if we do say that God has reasons for commanding and forbidding what he does? Then we say: God's reasons, the facts about our humanity and our universe that lead him to legislate what he does, are what make actions right and wrong. For example, suppose he forbids us to murder because murder is totally contrary to human happiness. Then we may say: the reason that murder is wrong is that it is totally contrary to human happiness. Do you see? Then God's reasons for saying loving each other is right will be just the same as our reasons for thinking loving each other is right.
The point then is that morality is, strictly speaking, conceptually separable from what God commands. In order to understand what is right and wrong, we need only understand what God's reasons for commanding things would be, if God were to exist. And that does not even require that God exists.
So in light of this, let us examine a claim brought out earlier: "If God is dead, then everything is permitted." Do you see now at least why I say that this claim is mistaken? If God were to have any reasons for what he forbids, those reasons are what make the forbidden things wrong. So it is perfectly possible to understand that we might lead moral lives, and accept very strong moral standards, even if we deny that God exists. We do not have to believe in God in order be rational in accepting moral principles.
In fact, later on this quarter we are going to spend a week and a half on issues in ethics, all strictly from a secular point of view. Ethicists, at least, certainly do not think they are out of work if they deny that God exists.
So I think this argument from morality is fallacious. Please notice, in saying this, I am not implying in any way, shape, or form, that God does not exist! I am also not denying in the least that God's commands are always right. What I am denying, rather, is that it is God's commands all by themselves which make actions right; I think that those commands would have to have some reasons behind them. And those reasons are what make the actions right. So I am simply saying that the argument from morality is not a good argument that God does exist. You can, as a theist, find much better reasons to support your belief in God.