My goal in this dissertation is to analyze the question, why is co-location a problem for the metaphysics of material objects? I believe that the existing literature on the topic identifies three possible answers to this question: Either, (i) co-location is a problem because it violates the no-coincidence principle, or because (ii) co-location violates the claim that the best available explanation for the relationship between objects that share the same empirically discriminable properties is the relationship of numerical identity, or finally because (iii) co-location violates the thesis of microphysical determination. I argue that (i), (ii), and (iii) are not sufficient reasons to think that co-location is metaphysically problematic, and that a denial of these assumptions does not warrant a rejection of co-location. I maintain that, instead, if co-location is a problem, it is so in virtue of violating a more basic assumption. Co-location is a problem for the view that the individuation and persistence conditions of any given material object is completely and solely determined by the physical or material properties of such an object. I advance reasons to believe that the latter view is fundamental in the sense that (i), (ii), and (iii), are consequences of it, and that co-location is in conflict with (i), (ii) and (iii), because it questions the basic physicalist view that provides the conditions for (i), (ii), and (iii). The fact that (i), (ii) and (iii) depend on the belief that physical properties exhaust the individuation and persistence of material objects, explains why they are not good reasons against co-location: They cannot establish that co-location is a problem for an account of material objects because they depend on the belief that co-location denies. Therefore, (i), (ii), and (iii) provide no more than three different ways of begging the question against co-location. I argue that, in order to show that co-location is a problem, we must show that physicalism with respect to material objects is the correct, or at least the most plausible, metaphysics of material objects, and this is something that neither (i), (ii), or (iii) can show. This statement of the relationship between co-location and anti-colocation reasons is also a contribution to the discussion of co-location. / Philosophy