Theirs is not the only modal ontology on offer. The main alternative to the KP theory has been the ‘modal realism’ championed by David Lewis (1986). Lewis's modal ontology appeals to objects called possible worlds, but these “worlds” are concrete objects. What we call the actual world is one of these concrete objects, the spatiotemporally connected universe we inhabit. What we call “non-actual” worlds are other concrete universes that are spatiotemporally isolated from ours (and from each other). There is, Lewis contends, a vast array of non-actual worlds, an array that contains at least those worlds that are generated by an ingenious principle of recombination, a principle that can be stated without the use of modal language (1986: 87). For Lewis, moreover, “actual” is an indexical term: when I speak of the actual world, I refer to the world of which I am an inhabitant—and so for any speaker who is “in” (who is a part of) any world.