Following oral arguments in Students for Fair Admission v. Harvard on Monday, it seems likely that the Supreme Court will strike down the use of “race-conscious” admissions policies at colleges on the basis that they violate the Constitution’s guarantee of equal treatment under the law.

The reason is twofold. First, Harvard and the University of North Carolina could not come up with a standard by which they might determine whether their campuses had reached the optimal level of diversity. Indeed, they couldn’t even explain to the justices what this optimal level of diversity might look like.