The Supreme Court rarely hears tax cases, and tax cases rarely threaten to affect the public at large. Moore v. United States, to be argued tomorrow, is that rare exception. The case raises an issue at once beguilingly simple and oddly difficult: What does income mean?

This is a question with ramifications for virtually every area of American taxation; depending on how the Court answers it, Moore could produce a chaotic ruling that casts constitutional doubt on huge swaths of the tax system. But it’s also a question that the Court doesn’t need to answer, and one that it shouldn’t.

The issue teed up in Moore may be so intellectually stimulating that nobody seems to have noticed that the case has been fundamentally misframed.