 Consider a second way of developing a challenge to the ethical realist, inspired by the Sidgwickian motivation for accepting ethical supervenience, introduced in  Section 2.  According to this motivation, we should accept an ethical supervenience thesis because doing so rules out the implausible hypothesis of brute ethical contingency. Intuitive Metaphysical clearly satisfies this motivation: it permits no brutely contingent ethical variation. However, suppose that it was not possible to explain why the ethical properties supervene on the base properties. Then the very thesis that we used to explain why there was no brute ethical contingency would turn out to be something arguably even more peculiar. It would be a metaphysically necessary connection that nonetheless has what Sidgwick might call an “arbitrary element in which we have to acquiesce;” in a slogan: a brute necessity.