Normative Externality

Let's say you want to say whether art is good. Well, there are different criteria of what good is in art. If something is very hedonic, it's good. But maybe at the same time it could be very anti-theistic, so it's bad.

There are cases when making art hedonic (or theistic) could make it anti-theistic (or anti-hedonic).

When a factory produces a product, that's (generally) a good thing in itself. But it could produce a dangerous byproduct in the process of doing that, and dump it in the river. We could call that an "externality".

A normative externality is when achieving a good state according to one value leads to a bad state according to another. Often, by "winning" in your own opinion, you might cause "losing" in someone else's opinion.