Sideline, does God oppose murder because it is wrong, or is it wrong because God has decreed it to be so?
Sorry, I completely missed this post before.
The way that this is phrased makes it kind of tricky to answer.
For one, I don’t believe that there is a god, so I have to do a little mental rearranging to figure out how to answer this. It isn’t exactly the same, but it would be a little like my asking if you believe that killing a unicorn is wrong, and if so why? The second problem is that murder is, as I’ve said before, immoral or wrongful killing.
In that case, it would seem to suggest that murder is wrong because it is wrong. Because a god who said something that was wrong, was right, is not a moral god.
(By the way, I’m trying to distinguish between generic gods and the Catholic God. If I mess up and use the lowercase, when I should use the uppercase, I apologize.)
However, as I’ve also discussed, there is a disagreement about when killing is wrongful. If we were to say that God gets to decide what is murder, and what isn’t, then killing doesn’t become murder unless God says it is. But in that case, morality is merely the whim of God. Saying “God is good”, is equivalent to saying “God is what God wants to be”.
So, to answer the question, you could argue that killing is murder when God says it is, but for murder to be truly wrong, it has to be wrong for some other reason. Otherwise, it is merely the opinion of a creator who decides these things arbitrarily.