 Armstrong also posits a wide array of “structural” universals: for example, given any universal property \(u_1\) and binary universal relation \(u_2\), Armstrong would hold that if there are any fusions of two non-overlapping objects individually instantiating \(u_1\) and jointly instantiating \(u_2\), there is a universal \(u_3\) that is necessarily instantiated by all and only such fusions. If the perfectly natural properties are those that correspond to universals, this view will lead to a great profusion of perfectly natural properties. This fits poorly with intuitive judgments of relative naturalness like those elicited by our initial examples, and threatens to disrupt several of the theoretical roles for naturalness (Sider  1995,  3). Lewis  (1986a)  argues (not on those grounds) that theorists of universals should not posit structural universals.