Realism, disagreement, and explanation

Morality and Mathematics by Justin Clarke-Doane (2020; hereafter “JCD”) is a richly argued and deeply original contribution to meta-ethics. My focus will be primarily on the arguments in Chapters 2 and 3, purporting to show that moral beliefs and mathematical beliefs are actually on a par when it comes to both a priori and a posteriori justification (what I will call the “Symmetry Thesis”).1 I start by saying something briefly about JCD's understanding of “realism” in Chapter 1, since it bears on some of the arguments in the chapters that follow.2