Just as we cannot read off what is real from what is basic, so we cannot read off what is unreal from what is nonbasic. Indeed, it is possible to imagine metaphysical scenarios in which the nonbasic, or grounded, is plausibly taken to be real. Suppose, to take one kind of case, that Aristotle is right about the nature of water and that it is both indefinitely divisible and water through-and-through. Then it is plausible that any proposition about the location of a given body of water is grounded in some propositions about the location of smaller bodies of water (and in nothing else). The proposition that this body of water is here, in front of me, for example, will be grounded in the proposition that the one half is here, to the left, and the other half there, to the right. But which of all these various propositions describing the location of water is real? We cannot say some are real and some not, since there is no basis upon which such a distinction might be made. Thus we must say either that they are all real or that none are. But given that the location of water is a factual matter, we should take all of them to be real, notwithstanding the fact that each is grounded in propositions of the very same sort. Another kind of case involves "horizontal" rather than "vertical" considerations. Imagine an ontology that takes certain simple events and the causal relationships between them to be real. Suppose now that one simple event causes a compound of simple events. Then this presumably consists in its causing one component of the compound and in its causing the other component. Now suppose that a compound of simple events causes a simple basic event, even though no component of the compound causes the event. Then it is not clear what the ground might be. But if this causal relationship is taken to be basic and hence real, then compound events should also be taken to be real, and so causation of the compound—which is a real relationship between real relata—should also be taken to be real, notwithstanding its being grounded in other causal relationships.
