Wow. I've been guilty of this for a while, and not realized it. That "is this action morally wrong" question really struck me.

Myself, I believe that there is an objective morality outside humanity, one that is, as Eliezer would deride the idea, "written on a stone tablet somewhere". This may be an unpopular hypothesis, but accepting it is not a prerequisite for my point. When asked about why certain actions were immoral, I, too, have reached for the "because it harms someone" explanation... an explanation which I just now see as the sin of Avoiding Your Belief's Real Weak Points.

What I really believe, upon much reflection, is that there are two overlapping, yet distinct, classes of "wrong" actions: one we might term "sins", and the other we might term "social transgressions". Social Transgressions is that class of acts which are punishable by society, usually those that are harmful. Sins is that class of acts which goes against this Immutable Moral Law. Examples are given below, being (in the spirit of full disclosure) the first examples I thought of, and neither the more pure examples, nor the most defensible, non-controversial examples.

• Spitting on the floor of an office building is a social transgression, but not a sin.
• Homosexuality is a sin, but not a social transgression (insofar as it is accepted by society, which is more and more very day).
• Murder is both a sin and a social transgression.

I do not know if this is a defensible position, but I now recognize it as a clearer form of what I believe than what I had previously claimed to believe.