 If some kind of combinatorialism is true, it could be a powerful tool for figuring out whether properties are perfectly natural, since many collections of properties that might otherwise seem good candidates to be perfectly natural seem to be involved in the kinds of necessary connections which, according to combinatorialism, never obtain among perfectly natural properties. The worry for those who want to use arguments like this to eliminate certain candidate collections of perfectly natural properties is that all the otherwise acceptable candidate collections might turn out to involved in such apparent necessary connections. If so we will face a choice between giving up combinatorialism and rejecting the relevant prima facie modal judgments. To illustrate the difficulties, we can return to the example of mass. Insofar as one takes physics as a guide to the perfectly natural, there is pressure to think that some perfectly natural properties have to do with mass. There are a great many possible candidates, including: