The theory of moral perception presented in Chapter 8 presupposes moral realism. Moral realism is controversial. Moral rationalists have defended it by drawing an analogy between mathematical knowledge and moral knowledge. It is commonly thought that mathematical facts, such as theorems, play essential roles in scientific explanations and that this explanatory power supports realism regarding mathematical objects. Do purported moral facts, such as true moral principles, have comparable explanatory power? This chapter explores several kinds of explanatory roles apparently played by both moral facts and mathematical facts. In comparing these roles, the chapter shows how moral realism is supportable in ways that draw on an analogy between the explanatory roles of moral facts and counterpart roles played by both certain mathematical facts and certain facts in the physical realm. The case made for moral realism is compatible with the view that moral properties are “naturalizable” but does not require this.

Chapter 9 explains Durkheim's understanding of moral facts and the conception of social solidarity at the core of his account of the division of labor's function in organized societies: crucial to what holds societies together and enables them to live are moral facts that inform relations among social members. Durkheim views human society as normatively constituted – governed by rules accepted as authoritative by social members – and claims that social institutions serve moral and not merely "useful" social functions. The chapter articulates the resources Durkheim has for conceiving of social pathology (itself an ethical phenomenon), examines the modern pathology most important to him, anomie, and coins a term for a related social pathology, hypernomie, a condition in which social rules are excessively rigid or constraining. Finally, the chapter reconstructs Durkheim's understanding of what is bad about social pathology – why social members should care whether their society is ill.