Crudely, ontology, at least in the context of metaphysics, is the study of what things exist. Obviously, this stands in need of some clarification. For instance, physicists set out to find out what things exist (are there black holes; Higgs-Boson particles; superstrings?) As too do biologists (what insects are there; what antibodies; what plants?) As too do archaeologists (does the lost city of El Dorado exist?); property speculators (is there any radon gas under such-and-such a house?); oil speculators (how much oil is there under the Arctic?); stamp collectors (what stamps are there?); and UFO watchers (are there any aliens?) ‘Are these people’, you might ask, ‘doing what you call ontology? Isn’t ontology something that everyone does?’ Of course, the answer is no – ontology is not something that everyone does, and the physicist, biologist, stamp collector and UFO watcher are not engaging in ontology even though they all have a vested interest in finding out what things exist. This is because the ontologist is not interested in the existence of any old things. You will not find ontologists rummaging around your wardrobe, scribbling down on a scrap of paper what things they find in there as they build their ‘list of all things that exist’. Whilst humorous, and whilst it would give me an excuse to rummage around other people’s private belongings without having to live out my childhood dream of being a private investigator, this is not what ontologists do at all. Indeed, there is virtually no fieldwork whatsoever, for ontologists are – unlike the physicist, biologist, UFO watcher etc. – interested in far more general questions about what exists. All of the examples cited above (subatomic particles, insects, antibodies, buildings, build-ups of gas, stamps and aliens) are examples of material objects. The ontologist generally accepts the existence of such material objects (but will, as we shall see in chapters 8 and 9, vary over the details). But this doesn’t even come close to exhausting the things that ontologists are interested in. Far from it! For they are not just interested in material objects, but interested in whether there are more things besides. By this, we don’t mean whether there are immaterial objects, like angels, God and the Devil (although some ontologists may be interested in that as well if they have an interest in the philosophy of religion), but whether there are things like numbers, properties, events, works of music, etc.
Let’s illustrate this with an example. A historian may tell us that, on 1 July 1916, 19,420 British soldiers died during the first day of the Battle of the Somme. Imagine the historian gave an ontologist detailed reports concerning what happened, and what went on, explaining what people were there, how much ammunition each side had, what terrain featured in the battle, and so on. The ontologist will probably agree that all of these things existed – they’re material objects and, with little exception, ontologists believe in material objects. But, they may ask, in addition to the material objects (the guns, the mud piles, the people involved, etc.), were there also things like events? In other words, if you listed everything that existed, would you write down not just all of the guns, the mud piles, the people and so on but also scribble at the bottom ‘The Battle of the Somme’? Or ‘the event of Private John Smith missing his target with his rifle’? Or any of the numerous events that took place during the Battle of the Somme? Or would you not stick those things on the list? Would you say such things didn’t exist, and that, in listing all of the material objects (the people, the guns, the geographic features, etc.), you’d have exhaustively listed everything that there was?
There are also more things than events to worry about. The Somme is a place. Do you have to put ‘The Somme’ on the list – that is, do places exist? Or consider this: many people were shot and were in pain. They had the property of being in pain. So do we have to add to the list of things that exist ‘the property of being in pain’? Or what about the fact that 19,420 people were killed? Does that mean that we need to add in numbers? Knowing full well that the number of people who were killed was 19,420, after listing all the material objects, properties and events that existed, do we stick down ‘the number 19,420’ on the list of all things that exist? Do we stick down every number (for surely if one number exists, all of them do)? We can even ask about the trenches. After all, isn’t a trench a hole in the ground – it’s a lack of earth that makes a trench and surely that lack, that absence, isn’t a thing in itself? Or do the tunes that the soldiers whistled during the day (however few and far between they may have been) get put on the list? And why stop the questions there! It’s possible that Private John Smith died during the battle even though he survived. So do possibilities exist? Do we have to add to our list of objects (and events, and absences, and numbers, and tunes, etc.) the possibilities that could have played out instead?
It is these kinds of questions that ontologists are interested in. They examine these broader, more general questions about what things there are. Each of the later chapters will deal with a specific category of things, in order: holes; properties; numbers; possibilities (and possible worlds); places (or regions, as we’ll call them); objects from other times; objects in general; and works of music. For this chapter, though, we’ll keep with elucidating how these kinds of questions even make sense. They are, after all, pretty esoteric sounding, and it’s not obvious that finding out whether there are numbers or not (etc.) is a worthwhile, or even intelligible, task. So let’s turn to examining some reasons for thinking that these questions are intelligible and intellectually worthwhile.
Abstract versus concrete
Start by introducing some basic terminology. Ontologists generally split things into two categories: the abstract things and the concrete things. When we say ‘concrete’, we don’t mean things made of cement – more than mere buildings get to be concrete in the ontologist’s use of the word. The concrete things are those things like particles, people, buildings, planets, goats, stamps, etc. ‘Concrete’, then, generally includes everything that is inside space and time, and usually extends to things like events and places. Indeed, if there are such things, people generally think that ghosts, God, and the Devil (i.e., immaterial things) are concrete. The concrete things (what we can call ‘concreta’) are the focus of the second half of this book.
Abstract things are things like the numbers, properties, possibilities, facts or propositions. Unlike the concreta, you won’t find abstracta anywhere. The number 4 isn’t down the back of your sofa, the proposition that 2 + 2 = 4 isn’t in Washington, the property being in pain can’t be found and picked up, taken home and sold on eBay (note that we italicize the names of properties). However, they might nonetheless exist (if you think it weird that things that aren’t anywhere nevertheless get to exist, I discuss this more below). So the abstracta are, crudely, those things which are not in space and time. They are sometimes said to be in platonic heaven, and if you read around the subject I’m sure you’ll come across that phrase. Plato believed that our world was just a sub-standard version of Heaven, whilst Heaven contained all of the ‘Forms’. The Forms were what things share when they have something in common. For instance, we are all human and so there is a Form corresponding to what it is to be human, and so all humans participate in these Forms (this is closely allied to the debate about properties that we shall discuss in chapter 3). Plato believed that they were abstract entities, and it has become common to say that they are ‘in’ platonic heaven (where ‘in’ is meant to be read figuratively, for they are abstract and so not really ‘in’ or ‘out’ of anything). So using the term isn’t to endorse the existence of a heavenly realm, but is just a shorthand way of saying that something is abstract, and not in space and time.
This is a very rough idea of what these terms mean, and when reading the literature you have to take what I’ve just said with a full tablespoon of salt rather than just a pinch. For instance, there is no agreement over what should appear on the list of abstract things and what on the list of the concrete. Some philosophers think that properties are in space and time (see chapter 3) and that possibilities are concrete things after all (see chapter 5). Moreover, my characterization of the divide being one of whether or not such things are in space and time or not is also pretty rough. Not everyone agrees with that (for instance, as already noted, some people place immaterial things in the concrete category even though they aren’t in space, and others use the word ‘abstract’ to apply to entities that are in time but that are not in space), and often the terms are defined differently as suits the purpose of the individual philosopher. But this rough idea will suffice for our purposes here.
‘Abstract’ and ‘concrete’ are good examples of where philosophers vary over defining terms. Throughout this book, boxes like these will make clear where there are problems in the literature with how terminology is defined. Not every philosopher uses the same term in the same way, and these boxes make clear when this happens. It is crucial, especially when doing your own independent reading around the subject, that you are clear on exactly what the individual author of a piece of work intends by using certain pieces of terminology, lest serious confusion set in.
Don’t get too hung up on asking what the ‘correct’ definition is. Words like ‘abstract’ and ‘concrete’ are terms of art, and one can freely make up a term of art and define it to mean whatever one wants – there’s no ‘right’ or ‘wrong’ about it! The differences don’t arise because someone is right and someone is wrong, but because metaphysicians haven’t all sat down and agreed what, precisely, the terms mean. Whether this is a good or bad thing – it’s probably not a great thing – it’s just a fact of life that, when you study ontology, you have to be keenly aware that different people might mean subtly different things by their terms, and that these subtle differences can often make for not-so-subtle consequences in any given argument.
Nonsense versus sense
Questions about concrete things will be far more familiar than questions about abstract things. If I asked you whether or not there was a hippopotamus in the next room, or whether there was a region of space a trillion light years away from earth, such questions are not radically different from questions you would’ve thought about before. Certainly there’s no reason to, say, think that such questions were either gibberish and meaningless, or trivial and not difficult to answer. The question about whether there’s a rather large water-dwelling mammal in the room next to me makes perfect sense; you can easily understand what that question means. Nor is it trivial to answer. You have to do something to find out whether it’s true or not, such as open the door and look, or just sit quietly and see if you can hear the sound of a confused two-ton hippo trashing an office. Similarly for the question about the region of space. Physicists do wonder whether or not there are regions of space that far away, and have spent time trying to determine the answer (which still remains unanswered). So, again, it is neither meaningless nor trivial. Likewise for all questions about concreta.
When it comes to abstracta, though, it is less clear that we can say the same thing. Some people think that corresponding questions about the existence of abstract things are somehow defective and so can’t be the subject of an intellectually informed debate. Let’s have in mind some specific examples:
- Does the number 7 exist?
- Does the property red exist?
- Does the possibility that I could be the president of Bolivia exist?
You might think that these questions are just gibberish. It’s not an uncommon response – just wander up to the next non-philosopher you meet and try and get them to tell you whether or not the number 7 exists and you might be met with a few odd glances or a lot of ‘What do you mean?’s. Such people might think the very question is meaningless. After all, not every string of words is meaningful. Whilst ‘Is there a panda pole-dancing over there?’ is an odd question, it’s meaningful. You know what it means for a panda to pole-dance (even though it’s unlikely to be the case that there is such a thing going on). Whereas the string of words ‘Panda over dancing there pole?’ is just meaningless gibberish. We might think of the above questions in the same light, such that they don’t even meet a standard whereby they mean anything in the first place. Questions like, e.g., ‘Do numbers exist?’ end up being as garbled as asking ‘Do numbers municipal?’
Alternatively, you might think that these questions make sense, but believe they are trivial to answer. For instance, we might think that it’s just obvious that there aren’t any such things. ‘Material objects exist!’ you might say, ‘But numbers? You can’t kick the number 7. You’ll never find it hanging in a gallery. We’ll never detect it through even the most powerful telescope. So how could it exist?’ All one needs is a closely held belief that one should only believe in things you can see (or otherwise empirically detect) and numbers get ruled out straightaway.
Finally, some people swing the opposite way. They believe that the questions are trivial but that it’s obvious that every such thing exists. For such people it’s just obvious that the number 7 exists. If it didn’t exist, what would three and four add up to? Similarly for the other categories. Properties obviously exist as, because we are both human, there is something that you and I both have in common. And if there’s something we have in common, then of course that property exists. After all, what does ‘There is a … ’ mean other than ‘There exists a … ’? If there is a property that we have in common, then there exists a property that we have in common. This triviality response is not an uncommon response either – just ask a mathematician whether there are any numbers and (unless she’s particularly philosophically minded) I’m sure she’ll happily ream off lots of them for you.
These are all gut reactions some people have when faced with ontological questions (although not simultaneously for, of course, they contradict one another). You might have these gut reactions, or you might not, but they’re certainly legitimate – that is, there’s something to each of them. The rest of this chapter goes through these gut reactions. Each reaction threatens ontology or, at the least, practising ontology as a live discipline. So we must dispense with them if we’re to think that ontology is a legitimate, serious subject. In summary, the problematic positions are:
Position One: Ontological questions about abstracta are meaningful, but very easy to answer such that entities like numbers etc. trivially exist.
Position Two: Ontological questions about abstracta are meanin...