Sarah McGrath deals with different topics on the basis of the «working hypothesis» that she states in the opening chapter, according to which moral knowledge can be acquired and lost in any of the ways in which we acquire and lose ordinary empirical knowledge. The hypothesisconsists of two parts: any source of empirical knowledge is also a potential source of moral knowledge; our efforts to acquire and preserve moral knowledge are subject to frustration in all of the same ways that our efforts to acquire and preserve ordinary empirical knowledge are. Chapters2, 3, and 4 are devoted to defending the first part of the working hypothesis, whereas the second part is defended in Chapter 5; the concluding chapter contains a summary of the theses argued for by McGrath.