  The distinction between possible being and being necessary through itself, which William draws from Avicenna, plays a prominent role in William's thought. William's notion of a possible is not that of something that exists in some possible world, but is rather the notion of something whose essence neither requires nor rules out its having being. William treats such possibles as in some sense prior to being. In the case of those that have being and thus actually exist, he holds that the possible “and its being (esse), which does not belong to it essentially, are really two. The one comes to the other and does not fall within its definition or quiddity. Being (ens) [i.e., a being] in this way is, therefore, composite and also resolvable into its possibility, or quiddity, and its being (esse)” (Switalski 1976, 44; Wade and Teske, 87). Some commentators see in such remarks the idea that a real or mind-independent distinction obtains between being and essence in possible beings.