TheExistenceOfPhysicalObjects

What does it mean to say that a physical object exists? Let’s take for granted, for the time being, that we know what a physical object is. The question is what it means to say that that sort of being exists. Or, if you prefer, I want us to fill in the blank in the following: "An object exists, if and only if, it ... ." That would give us a definition of the word "exists" in the sense in which that word applies to physical objects.

Some people have thought that this question cannot be answered. They think that "exists" just cannot be defined. They think that we all very well understand what it means to say that an object exists, but we can’t define it. This is a very influential view, which many very smart people hold. So we’ll will come back to it. But let’s at least start by assuming that we can define "exists" for physical objects. How could we start?

Well, here’s a place to start. What is existence constrasted with? Well, nonexistence; but there are different kinds of nonexistence, right? Think of all the different ways that something we talk about nevertheless fails to exist. For example, in stories: we say Romeo and Juliet do not really exist, because they are merely characters in a play. So there is fictional nonexistence, that’s one kind of nonexistence. Or suppose you’re just daydreaming and you imagine winning the Nobel Prize. Well of course your Nobel Prize does not exist: it’s just imaginary. So a second kind of nonexistence is imaginary nonexistence. (Or you might say, "It has existence only in your imagination.") Or consider that old hypothesis, that the Earth is flat. People who thought the Earth was flat thought there was an edge to the world, and if you sailed too far across the ocean you would sail off the edge of the world. Well, as we all know, the world is not flat but roughly spherical, and the edge of the world doesn’t exist. So that is a third kind of nonexistence: hypothetical nonexistence. In other words, that’s the sort of nonexistence that false posits have, when you posit something in a false hypothesis. And now here’s a totally different kind of nonexistence: namely, the kind the ancient Greek philosopher Socrates now has. Socrates does not exist now. He did exist, but there’s a sense in which he doesn’t exist; namely, he doesn’t exist any longer. So the fourth sort of nonexistence is past nonexistence. And of course then, fifth, there would have to be a corresponding future nonexistence. The person who will be President of the United States 200 years from now does not, now, exist.

Hopefully this gives you a very vivid idea of what it is that we’re talking about when we say that a physical object exists. We say: it’s actually in the world, it’s not fictional; it’s real, not imaginary; it’s an actual phenomenon, it’s not part of a false hypothesis; and it’s located at the present time, not just at a past, or a future time.

Now, there may be many different senses in which objects can fail to exist; but it would appear there is only one basic sense in which physical objects actually do exist, and that is as an object that belongs to the space-time system that is the world with which we are in direct contact. If we can bump into it, it exists. So we might boldly give this following definition:

Physical object O exists if, and only if, O is, at present, spatially located in the universe with which we are in contact.

This is, I think, a plausible definition of "exists," one that expresses the common sense notion of existence. But it’s just an attempt, of a sort that a few, but only a few, philosophers have given. Aune, from our reading, for example, gives a definition much like this one. So suppose now you’re back in the room with the big red apple. According to this definition, to say that that apple exists is just to say that right now, it has some location in space, that is, in the space that your body is also part of. So in other words you are at some distance from the apple right now. That’s approximately what it would mean to say that the apple exists.

Consider how it is that those five different kinds of nonexistent objects fail to exist according to this definition. First, fictional characters. In fact, Romeo is not spatially located anywhere. So he doesn’t exist. Second, imagination. The imaginary Nobel Prize is not located anywhere in relation to the universe I see around me now. So it doesn’t exist. Third, false hypotheses. Well, the edge of the world is not, in fact, located anywhere in the world; the world doesn’t have an edge. So the edge of the world doesn’t exist. Fourth, past and future. Socrates from ancient Greece, and the President in the distant future, are not at present located anywhere in relation to the universe that I am a part of, not at present.

As you might suspect, this sort of definition encounters some serious objections. Next, we’ll consider one of these objections, probably the most widespread.

There are many philosophers today, following Kant and Russell, who claim that existence is not a property. This is a rather strange thing to say. Now, I exist, and the Eiffel Tower exists. These are both true claims, and they both make perfect grammatical sense. It seems like I am saying that existence is a property of me, and of the Eiffel Tower. And yet many -- not all, but many -- philosophers deny that existence is a property.

Well, first of all, you might be wondering why it matters at all whether or not existence is a property. Here’s how it matters. If existence isn’t a property, then the concept of existence cannot be defined, or at least, not the way we have defined it. Our definition of "exists" is incorrect just because our definition does treat existence as a property. It starts out by saying "Physical object O exists if..."

All right. Many people have said that the influential German philosopher Kant had an argument with the following conclusion: existence is not a property. (When you get home, look on p. 42 of the packet for more about Kant’s argument.) I’m going to try to explain how I understand this argument. So here goes. Suppose we listed out all the properties and relations of our apple. It’s red, it has a stem, it’s four inches wide, it’s juicy, it’s on the table, it’s in the room, and so on. Kant says, then, once you’ve listed out all the properties and relations of the apple, you could try saying that the apple exists. But that wouldn’t add any new property to the thing, Kant says. Therefore, existence is not another property over and above all these. So in other words, Kant argues as follows: a complete list of an apple’s properties would not be expanded by adding another property, namely existence; therefore, existence isn’t another property over and above all the other properties.

So -- does that mean that existence is not a property at all? Well, no. If I list out all the properties of the apple, my list would include "being located in the universe with which we are in contact." I’m saying that that particular property just is what makes the apple exist. That property would, of course, be included in a list of all of the apple’s properties; so then look at this claim of Kant’s, that existence isn’t another property over and above all its other properties. Well, that’s right, it’s not another property. But that by itself doesn’t mean that existence isn’t a property at all! So Kant’s argument, as far as I can tell, just doesn’t prove its alleged conclusion.

Well, let’s look at how John Hospers interprets Kant’s argument, on p. 42 of the packet (this is reading you’ll have to do next week). Maybe Hospers can make Kant look better. To quote Hospers:

If we say that a horse has a mane, a tail, four legs, and hoofs, we are attributing properties to the horse; but if we go on to say that the horse exists, we are not adding another property: we are saying that the thing we conceived as having these properties also exists. We are not adding to our concept of the thing: we are asserting a relation between the concept and the world.

Hospers says here that when we say that a horse exists, we aren’t attributing a property to the horse; we are "asserting a relation between the concept," the concept of the horse, "and the world." That’s what he says; but if you think about what that’s saying, you can see that it’s not quite right. To say the horse exists isn’t to assert something about the relation between the concept of the horse and the world; it is to assert something about the relation between, well, the horse and the world! Namely, that the horse is in the world! And we can have a concept of a particular horse that exists, and that concept would have that horse located in our world; and we can also have a concept of a particular horse that doesn’t exist, and that concept would have that horse not being located in our the world. So as far as I can tell, Hospers’ argument isn’t valid. It just doesn’t prove that existence isn’t a property. All that it proves -- and it does prove this -- is that existence isn’t a different property from the other properties of a thing. Yeah, so what?

But the dialectic definitely doesn’t end there. Much more can be said on both sides. To really get to the heart of why so many philosophers these days think that existence can’t be defined, we would have to explore a lot more logic. We just don’t have the time or the background to come to grips with that. But if you’re interested in the issue you should read p. 42 of the packet very carefully, and I can talk to you more about it after class.

That’s all I intend to say about the question of what it means to say that a physical object exists. If you thought there was nothing to be said about that question, I hope you have been pleasantly surprised. In fact, there is a lot more that we could say about that question.