 Tropes are typically taken to be simple, i.e., without any subconstituent (see Section 2.2 of the entry on  tropes).  Their playing the role of states of affairs with universals as constituents depends on this: universals combine two functions, only one of which is fulfilled by tropes. On the one hand, universals are characterizers, inasmuch as they characterize concrete objects. On the other hand, they are also unifiers, to the extent that different concrete objects may be characterized by the very same universal, which is thus somehow shared by all of them; when this is the case, there is, according to the universalist, an objective similarity among the different objects (see  §1.2).  In contrast, tropes are only characterizers, for, at least as typically understood, they cannot be shared by distinct concrete objects. Given its dependency on one specific object, say, the apple \(a\), a trope can do the work of a state of affairs with \(a\) as constituent. But for tropes to play this role, the tropist will have to pay a price and introduce additional theoretical machinery to account for objective similarities among concrete objects. To this end, she will typically resort to the idea that there are objective resemblances among tropes, which can then be grouped together in resemblance classes. These resemblance classes play the role of unifiers for the tropist. Hence, from the tropist’s point of view “property” is ambiguous, since it may stand for the characterizers (tropes) or for the unifiers (resemblance classes) (cf. entry on  mental causation, §6.5).  Similarly, “exemplification” and related words may be regarded as ambiguous insofar as they can be used either to indicate that an object exemplifies a certain trope or to indicate that the object relates to a certain resemblance class by virtue of exemplifying a trope in that  class.[6]