  The simplest challenge notes that Leibniz equivalence is a standard presumption in the modern mathematical physics literature and suggests that even entertaining its denial (as manifold substantivalists must) is some kind of mathematical blunder unworthy of serious attention. While acceptance of Leibniz equivalence is widespread in the physics literature, it is not a logical truth that can only be denied on pain of contradiction. That it embodies non-trivial assumptions whose import must be accepted with sober reflection is indicated by the early acceptance of the hole argument by David Hilbert. (See  Section 8.2  above.) If denial of Leibniz equivalence is a blunder so egregious that no competent mathematician would make it, then our standards for competence have become unattainably high, for they must exclude David Hilbert in 1915 at the height of his powers.