Our simplified version was that "A ought to do X" means that "Under circumstances C, if A does not do X, A would be breaking a rule in an applicable moral system."

It seems to me that any useful analysis of "X is good" should allow us to account for the fact that people argue about what is good. We do have serious moral disagreements. And these disagreements can be especially harsh when people disagree fundamentally. Now, let's say that two people (or two cultures) make moral judgments using two different sets of rules or principles. On Wong's definition, both judgments may be true. It looks as though there is no disagreement. But isn't that a mistake?