What is an Ersatz Part?

_ Source: _Page Count 28 This paper develops four proposals for explicating the notion of an ersatz part. It then evaluates each proposal with respect to a number of jobs for which ersatz parts are posited. We argue that each of the four notions of ersatz parthood do better with respect to some jobs, and worse with respect to others. Thus, we think, it’s horses for courses: which notion of ersatz part one chooses will be sensitive to which metaphysical project one is pursuing.