If in such cases the bare statement of the facts and the outcome cannot tell us what the precedent case fully "stands for," then it is tempting to say that the question of legal similarity is itself determined by the law. That is why discussions of precedent, including Goodhart's, commonly talk not about facts but about material facts. In concluding that the holding of the case-the term more common in the United States than ratio decidendi, although there are slight differences in meaning-is a combination of the material facts and the outcome, Goodhart and others solved the level of generality problem, but at the cost of undermining the core of their view. So to Goodhart it would have been an error to say that the car being a Buick was a material fact, because the car's "Buickness" was no more material than the fact that Mr. MacPherson's last name began with the letter "M." Under this view, a fact is material when a legal rule makes it legally important. It is a legal rule that tells us when two things are similar, and thus it is a legal rule that tells us the level of generality at which the facts should be understood and described by the deciding court. It is therefore a legal rule that would tell us that "automobile" is a legally material category while "Buick" is not. But although this is often so, relying on a legal rule to tell us which cases are materially similar and which are not avoids the very question we are trying to answer. If the standard for materiality comes from outside the precedent case-a statute, for example-then the statute is doing the work and we do not have an example of precedential constraint at all.

Unknown, Frederick Schauer - Thinkin…, loc. 91