 Assuming we agree that there is something that needs explaining (i.e., assuming we agree that how several tropes can—contingently—make up one object needs explaining), we can either reject a proposed solution because we prefer what we think is a better solution, or we can reject it because it is in itself bad or unacceptable (irrespective of whether there are any alternative solutions on offer). MacBride appears to suggest we do the latter. More precisely, what MacBride proposes is that the solution fails because it leaves unexplained the special ‘power’ to relate it attributes to the compresence trope. If this is why the suggestion fails, however, then either this is because no explanation that posits something (‘primitively’) apt to perform whatever function we need explained, is acceptable, or it is because in this particular case, an explanation of this kind will not do. If the former, the objection risks leading to an overgeneration of explanatory failures. Everyone will at some point need to posit some things as fundamental. And in order for those fundamental posits to be able to contribute somehow to the theory in question, it seems we must be allowed to say something about them. We must, to use the terminology introduced by Schaffer, outfit our fundamental posits with axioms. But then, as Schaffer also points out (2016: 587): “it is a bad question—albeit one that has tempted excellent philosophers from Bradley through van Fraassen and Lewis—to ask how a posit can do what its axioms say, for that work is simply the business of the posit. End of story”.