I think that if we were left to our own devices, we would be able to work out for ourselves when we were doing something wrong. Maybe if it was nothing more than that small voice inside us saying: ‘Hey, I’m not sure I should be doing this’ (and yes, maybe that could be God).
But there are things that we do sometimes, such as premarital sex, when that little voice can be completely silent (if the little voice is God, then why is He so silent on some of these occasions?).
If you are a small child, you may not be aware that taking a toy from another child is wrong. At a young age you need to be told. But as you get older, you can see that taking it deprives someone else. You can see that there are negative consequences. So any mature adult should be able to distinguish from right and wrong. Which doesn’t prevent them from doing wrong, but at least they know what they are doing.
This is an interesting thought, although I think it would be difficult to work out the modality of the bolded statement (ie. “would be able to…”). I think there is some valid intuition that, yes, we admonish children and they are not always expected to behave as they ought, while adults we hold morally responsible for their errors.
However, I think there are opposing intuitions as well. Children sometimes have moral intuitions that adults do not; when they do something wrong, they may feel very guilty, or when a parent steals something from a store, they feel that it is wrong. By contrast, I agree that “any mature adult should be able to distinguish from right and wrong” (in the sense that they are culpable if they do not), but that doesn’t entail that they have something akin to a “little voice”
telling them that they are wrong. In short, adults can go wrong, and when they do so, they are culpable.
But it is psychologically false that in doing so adults are (in general)
conscious of their moral violations; there is enormous evidence of widespread moral self-assurance. Adults are often jaded and stuck in bad habits. Observe any argument on the internet; at least one side is arguing for a morally deficient position and almost everyone feels self-righteous. I know I sometimes observe my parents saying that they are justified where, in my view, they clearly are not–and I don’t think that is an unusual phenomenon.
So if there are no negative outcomes from having premarital sex, then it is, by definition, not wrong.
This depends on what you mean by “negative outcomes.” That category can be construed broadly enough that the above statement is essentially a tautology; for example, there might be intrinsically wrong acts, one of which is premarital sex, in which case all premarital sex necessarily has a negative outcome, making the above statement necessarily true.
I suspect you mean something more specific by “negative outcomes”–maybe an act has negative outcomes only if some person (justifiably*?) involved in the act believe themselves to have been hurt by the act. This is a more tendentious and controversial claim. (Since the idea that this follows from the definition of “wrong” would beg important questions.) One issue is that the lack of negative outcomes would have to be underwritten by some index of premoral goods, which is difficult to specify. Another issue is that it would justify other more controversial behavior; two brothers or a father and daughter using birth control could probably have sex without “negative outcomes” under this construal. (One may regard such behaviors as fine anyway. This is mainly meant to highlight how controversial such a principle would be, since it is usually denied that contemporary sexual mores entail the permissibility of incest.)
*I hesitate to add this qualification. Leaving it out would make it too easy for people to claim that an act is wrong. But adding it in would of course require that what is justifiable be explicated, and then the account of negative outcomes is not autonomous. There is probably a neater way to handle these issues, but I’m tired right now.
