 The dispositionalist holds that the essence of a property \(P\) is wholly constituted by the nomic or causal roles \(P\) plays—for short, theoretical roles. Here the nomic role of \(P\) is given in terms of the Ramsey sentence that we can get from a true and complete final theory, a sentence that represents the totality of the factual content of the theory. The causal role of \(P\), on the other hand, is given in terms of its potential causes and effects.  Dispositionalism thus implies the following transworld identity condition for properties: properties \(P\) and \(Q\) are identical iff they play the same theoretical roles. (This identity condition smacks of circularity since theoretical roles can be plausibly considered as high-order dispositional properties. This issue is discussed in detail in   Appendix.) Note that the theoretical roles played by a property \(P\) determine how its instances are disposed to act or react under various circumstances. On dispositionalism, therefore, \(P\) invariably endows its instances with the same dispositions, in which sense dispositionalism implies that properties have dispositional essences—and only dispositional essences.