It is often claimed by Christians that God is the ultimate arbiter of morality and either defines or personifies ethical behavior. It is said that what God commands is moral by definition.

I can understand believing this in concept, but what I don't understand is how one could responsibly arrive at such a position. To explain let us start with a mostly blank slate of a person who has some ethics instilled by their upbringing and society, but hasn't thought much about them and doesn't believe in a god yet. Let's call him Sam.

Now Sam wants to be a "good person", whatever that means. In order to figure out how he should act he must necessarily use his noggin and think about ethics. Either his ethical reasoning is perfect or it isn't; if it is perfect the only question is how well he can adhere to the standard he figured out for himself.

If Sam's ethical reasoning is perfect then anyone who comes peddling a god is in for a hard time. If their god's commands don't perfectly align with Sam's views then it isn't a good god, and if they do then it is superfluous. What moral guidance could it offer but aid in Sam adhering to his ethics, which would be open to testing (and we all know where that goes)?

On the other hand if Sam's reasoning is flawed he can use an ethical guide such as what theists offer. But how does he choose? If a God's ethics perfectly match his own then the God is just as flawed as Sam. But if they differ from his own view, how does he distinguish a god being different and right from a god being different and wrong?

If instead of ethics we were assessing navigation skills then we could simply run some tests. Even if Sam couldn't always tell a correct turn from a wrong turn, he can identify if the destination is properly reached and determine if the god can get there more reliably than he can.

But ethics is of course different. Sam has no method of assessing ethics which he knows is more reliable than his own reasoning, because any proposed method or standard must be assessed by his own reasoning!

Now Sam of course isn't everyone; people pick up their morals by upbringing and often the justification for such morals is cited to be outside authorities such as a god. But I argue that everyone should be Sam if they want a better justification for their morals than "Someone I trusted told me when I was really young and I believed them because I wasn't able to think for myself, and now that I'm in it works fine." The first leap there was unjustified and unethical, which taints the later conclusions as the foundation is bankrupt.

How then do Christians propose that Sam could responsibly come to believe that God's standards of ethics are superior to his own, and give up his moral reasoning?