I'm not thinking of rules in terms of "thou shalt not..." - that's imposing an obligation. A rule is rather a pattern, in this case a pattern of behaviour - like being kind. — Banno

Would a philosophy of psychology touch on things like: what if people are fundamentally different in ways that don't show up on the surface. Jim's actions are guided by his vision of consequences. Jane tries to treat others the way she wants to be treated. Maybe there are a lot of ways people experience motivation.

And since that kind of difference could exist without our knowing it, we might well treat ethics empirically. Just observe what people say is right and wrong and so forth.