One common argument for the existence of God is the moral argument, which says that the best explanation for humanity's shared sense of right and wrong is a god who sets an objective standard. I've discussed with the Morality Argument before, but I'd like to bring up one particular question that comes up for people who subscribe to this argument: The Euthyphro dilemma:

ἆρα τὸ ὅσιον ὅτι ὅσιόν ἐστιν φιλεῖται ὑπὸ τῶν θεῶν, ἢ ὅτι φιλεῖται ὅσιόν ἐστιν

Which translates to "Is the pious loved by the gods because it is pious, or is it pious because it is loved by the gods?" When dealing with Christianity, the dilemma can be phrased like this: "Is what is moral commanded by God because it is moral, or is it moral because it is commanded by God?"

If God commands things because they're moral, then that means there is some standard of morality above and outside of God and he's only passing it on to us.

If something is moral only because he commands it, then morality is arbitrary. If God wanted to declare that genocide is allowed, then it would no longer be evil. If God is the very definition of good, then saying "God is good" is meaningless. You might as well say that that the book 1984 is Orwellian.

The standard Christian response to the dilemma is to say that goodness flows from God and is one with his very nature. I don't think that really avoids the problems of the dilemma, but I'm not bringing this up in order to settle the issue. I only want to point out that there is a dilemma. It doesn't disprove the existence of God, but it does show that the Moral Argument is not without its problems. I think that there are better explanations for our shared morality than god that are simpler, fit better with the facts and raise fewer questions.

Note: I encountered the Euthyphro Dilemma while reading a review of Reasonable Faith by William Lane Craig. The review was written by Chris Hallquist and I recommend it. And yes, this is all a thinly veiled excuse to add Greek to a post.