ABSTRACT
The ontological question, according to Quine, asks “What is there?” Biologists, chemists, physicists, zoologists, and many others supply us with some provisional answers: There are trees, molecules, bosons, horses, and so on. Reasoning about our commonsense beliefs can supply us with further answers. Ontologists look more deeply into such provisional answers and ask which of them are true and which only appear to be true. One might wonder why we should want to do ontology. It is
annoying to respond to a question like “Where are my keys?” by saying, “Well, how do you even know you have keys? Do keys really exist?” Commonsense belief in the reality of keys is useful. It helps get us around in the world. It is “empirically adequate”; it is not the sort of belief that will be seriously called into question by observation or experiment. But if empirically adequate beliefs about what exists are all that we need to get around in the world, why should we try to look any deeper? The answer is that sometimes ontological questions do bear on
matters of great concern. Though it is hard to see how questions about the reality of keys make a difference to anything we care about, it is not at all hard to see the importance of questions like “Is there a God?” or “Do I have a soul that can survive the death of my body?” or “Am I free?” or “Do my commonsense intuitions
about what exists in the world and about what the world is like lead me badly astray?” Our answers to these questions will be intimately connected with various ontological questions. Sometimes ontological questions are the questions we care about. Sometimes they bear only indirectly on the questions we care about. Either way, they are still important. Suppose you think that there are immaterial souls and that they
are invisible and not physically located in spacetime. Someone might tell you that it is unreasonable to believe in things like that. Can you sensibly reply that it is reasonable to believe in numbers and say that numbers are like that? That depends on whether it is reasonable to believe that there really are numbers. Similarly, as we shall see in a later chapter, it is remarkably easy to show that commonsense beliefs about material objects lead us into contradictions. Learning this, one might just shrug it off and concede that our commonsense conceptual framework is an incoherent mess. Many of us, however, would prefer to see whether we can avoid such contradictions by thinking harder and more carefully about what really exists. It is disturbing to think that our commonsense intuitions are wildly unreliable. So many philosophers have been interested in examining those intuitions to see just how much commonsense ontology can be saved. Sometimes the result of this process is that we reach conclusions like “There are no nonliving composite objects,” which then have implications for questions about whether our keys or our dining-room furniture really exist. So, even if those latter questions are not, all by themselves, of philosophical interest, they come to be of interest because of their connection to other questions which are of deeper and more lasting philosophical import. As a general rule, people seem to avoid believing in things that
seem weird, especially things that cannot in principle be detected by sensory experience or instruments, and things belief in which leads to paradox. I suspect that this general preference goes some distance toward explaining why, in contemporary ontology, questions about the existence of abstract objects, nonexistent objects, creatures of fiction, God, souls, and composite material objects of various kinds have tended to dominate the literature. Abstract objects are things like the number two, the set of all horses, beauty, and so on. They are the sorts of things that cannot even in principle
be detected by sensory experience or instruments. (We see beautiful things, not beauty itself; we see horses, but not sets thereof, and so on.) If they exist at all, they are immaterial, (probably) have no location in spacetime, and lack causal powers. They are weird. Many philosophers do not wish to believe in them. Belief in God and souls has seemed problematic for similar reasons, though God and souls are usually classed as concrete objects by virtue of their alleged causal powers. Creatures of fiction and nonexistent objects are not only weird but paradoxical. For example, we seem often to talk about such things. Peter Parker (a.k.a. Spiderman) works at the Daily Bugle and engineered his own web-shooters. But neither Parker nor the Daily Bugle nor Spiderman’s web-shooters exist. How could both of the previous two sentences be true? Ponce de León spent a good deal of his life searching for the Fountain of Youth, which seems to imply that he spent a good deal of time searching for a thing that does not exist. But it sounds contradictory to say that there is a thing that does not exist. Composite material objects also present us with paradoxes-enough, in fact, that some philosophers have decided that the best overall response is simply to deny the existence of composite objects altogether. In the present chapter, we shall focus primarily on questions
about the existence of (certain kinds of) abstract and nonexistent objects.
