 Discussions of supervenience often appeal to property sets that are closed under such operations. But this is not a trivial assumption, for two reasons. First, it is controversial whether complementation, conjunction, and disjunction are legitimate property-forming operations. Whether they are largely depends upon what properties are taken to be. If properties are just the semantic values of predicates, then there are negative, conjunctive, and disjunctive properties, because negative, conjunctive, and disjunctive predicates can have semantic values. But if properties are universals there may not be any such properties (Armstrong 1978, 1989). And if properties are ways a thing might be, then property sets cannot be closed under Boolean operations. That would entail that for any property F, being F and ~F is also a property. However, that is not a way anything might be. Second, even if it is assumed that the property-forming operations are legitimate, the fact is that we are quite often interested in property sets that are not closed under them. Consider negation. Even assuming that there are negative properties, the fact is that we do not standardly count cats as having geological properties because they are neither ignaceous, sedimentary, nor metamorphic. And it seems strange to say that Descartes was committed to mental substances having physical properties simply because he thought they are not spatially extended. Since not every property set is closed under every property-forming operation, supervenience is not in general sufficient for entailment. (For further discussion of supervenience and various property-forming operations, see Van Cleve 1990; Oddie and Tichy 1990; Bacon 1990, 1995; Glanzberg 2001; Bader 2012.)