Parfit's On What Matters offers a rousing defence of non-naturalist normative realism against pressing metaphysical and epistemological objections. He addresses skeptical arguments based on (i) the causal origins of our normative beliefs, and (ii) the appearance of pervasive moral disagreement. In both cases, he concedes the first step to the skeptic, but draws a subsequent distinction with which he hopes to stem the skeptic's advance. I argue, however, that these distinctions cannot bear the weight that Parfit places on them. A successful moral epistemology must take a harder line with the skeptic, insisting that moral knowledge can be had by those with the right kind of psychology -- no matter the evolutionary origin of the psychology, nor whether we can demonstrate its reliability over the alternatives.
Along the way, I also (1) argue against Street's "normative lottery" analogy; (2) argue that her constructivist view is self-defeating; (3) introduce an "internalist" version of reliabilism; and (4) offer an analysis of when it makes a difference whether some possible disagreement is actual.
I still have a couple of months to put on the finishing touches, so any suggestions would be most welcome!