The first response says: so much the worse for tropes and immanent universals. This response uses a mereo-locational principle, No Interpenetration, as a premise in an argument against certain metaphysical views, namely those that posit tropes or immanent universals. Is there some reason why mereo-locational principles should not be used in this way? The principles of pure mereology are often so used. For example, Lewis (1999: 108–110) rejects states of affairs and structural universals on the g