What makes something a part of my body, for moral purposes? Is the body defined naturalistically: by biological relations, or psychological relations, or some combination of the two? This paper approaches this question by considering a borderline case: the status of prostheses. I argue that extant accounts of the body fail to capture prostheses as genuine body parts. Nor, however, do they provide plausible grounds for excluding prostheses, without excluding some paradigm organic parts in the process. I conclude by suggesting (...) that embodiment is moralized all the way down: to be a body part is to be the sort of thing that ought to be protected, in a certain way, by social practices. (shrink)