So now letís talk a bit about the field of metaphysics in general, before we consider some particular metaphysical problems. And letís begin with the origin of the word "metaphysics." Now, the ancient Greek philosopher Aristotle wrote a number of books which together he called the Physics. The way that the books of Aristotle were organized in an early edition, there was another set of books that were placed right after the physics. These books seemed to concern a really basic, fundamental area of philosophical inquiry, which up to that time did not have any particular name. So early Aristotle scholars called those books "ta meta ta physika," which means "the books that come after the physics." So thatís where we get the word "metaphysics." Metaphysics is supposed to be the subject of those books by Aristotle which were called, collectively, the Metaphysics. So etymologically, what "metaphysics" means is "the subject that the Metaphysics of Aristotle is about."
But this just begs the following question: What were those books by Aristotle about? The books were divided into three parts, called (1) ontology, (2) theology, and (3) universal science. So ontology, theology, and universal science are regarded as the three traditional branches of metaphysics. We arenít going to go into this division of metaphysics in much depth because I donít think it is very helpful. But just to explain, very briefly, what these three terms at least mean. (1) "Ontology" is the study of existence; it has been traditionally defined as "the science of being qua being." If you donít know what that means, youíre not alone; more about it in just a bit. (2) "Theology" means, here, the study of God or the gods (remember, weíre talking about ancient Greeks here) and of questions about the divine. (3) "Universal science" is supposed to be the study of so-called first principles, which underlie all other inquiries; an example of such a principle is the Law of Non-Contradiction: "A thing cannot both be and not be at the same time, and in the same respect." Our apple cannot both exist and not exist. So that was the Aristotelian conception of metaphysics.
Metaphysics has changed a lot since then, over the many centuries of its existence. Problems that were not originally considered metaphysical were added to metaphysics. Other problems that were for centuries considered metaphysical problems are now pretty much relegated to their own separate subheadings in philosophy. For example, there are a lot of problems that used to be considered part of metaphysics, but are now more commonly considered parts of the philosophy of religion, philosophy of mind, philosophy of perception, and philosophy of science. So needless to say, it would take us a long time even to state all the problems that have, at one time or another, been considered part of metaphysics.
But you might be asking this: Can we give some rough-and-ready account of what made all of these different problems "metaphysical" problems? I think so. We could give the following very rough, inexact definition of "metaphysics": Metaphysics is the study of any of the most fundamental philosophical beliefs, on which many other philosophical beliefs rest.
And you could ask this too. Suppose we consider only the core metaphysical problems. The core problems would be the ones which have always been considered metaphysical and which have never been considered not metaphysical. Is there something that distinguishes those problems?
I would think that most of such problems are part of Aristotleís first branch of metaphysics, or ontology, and ontology, remember, is supposed to be the study of existence, or as Aristotle says, "the science of being qua being." So Iím saying the core metaphysical problems are, at least mostly, problems about "being qua being." But this must be frustrating to hear because you donít know what "being qua being" means! Iíll give a go at explaining what it means, and that way you can learn what "ontology" means.
First I need to explain what the word "being" means here. I would suggest the following as a rough gloss:
A being is anything that can be said to "be" in various senses of the word "be."
Now, you remember from last time that many words are ambiguous -- which means they have various different senses. "Be" is a word, like many other words, that has different senses. So there are different senses of the word "be," and accordingly, there are different kinds of beings. Because, as I said, a being is anything that can be said to "be" in various senses of the word "be."
The different kinds of being are called categories of being. Letís go through a few of these categories of beings. That should give you an idea of what weíre talking about when we use the words "being" and "category" of being. Just bear in mind that different philosophers make different lists of the fundamental categories of being; and one of the basic questions of ontology is: "Just what are the fundamental categories of being?" Anyway, in no particular order, here are at least some categories of being.
First category. Physical objects. Physical objects are beings; certainly they are said to be in the simple sense that they exist all around us. So a house is a being, a personís body is a being, a tree is a being, a cloud is a being, and so on. They are beings because, and in the sense that, they are physical objects. You might also call them bodies, or concrete things, or maybe "substances" -- but the word "substance" has some special philosophical meanings as we'll see. For a neutral term Iíll usually use either "object" or "body."
Second category. Minds. Minds -- those the parts of us that think and perceive -- are beings. Each of us, we say, has a mind, a mind that exists or has being. So each of our minds is a being. Now I donít mean to imply that minds are necessarily a different category of beings from physical objects. But many people have thought so and you probably think so yourselves. More about that in a few weeks.
Third category. Classes. We can talk about human beings, and planets, and engines as classes of things. In the class of human beings is all of the human beings; or, to use terminology from last time, the extension of the term "human being." In the class of planets would be Mercury, Venus, the Earth, etc. -- all the planets that there might be in the universe. Iím saying that classes, in addition to each of their members, are often taken to be beings. Surely we can say that in some sense, the class of engines is, or has being.
Fourth category. Properties. The redness of our red apple on the table is a property. You could also call it an attribute of the apple. Everyone in this room, I think, has the property of having hair. So very roughly put, a property is just a quality that describes an object. Of course that wonít do as a definition of the word "property" because, like "attribute," "quality" is a near-synonym of "property." And remember, itís not particularly helpful to give philosophical definitions using near synonyms. But these synonyms can at least help us to get a fix on the concept weíre talking about. Iím just going to blur over any distinctions that have been drawn between the terms "property," "attribute," and "quality"; for purposes of introducing this material the distinctions donít matter. Anyway, whenever you talk about the size, color, weight, composition, and so forth, of an object, youíre talking about the objectís properties. My claim then is that properties are beings; the redness of the apple is something that is.
Fifth category. Relations. The apple is in a relation to the table it sits on. So we can say that there is a relation between the apple and the table -- namely, the relation of "sitting-on." So we can say that that relation has being. Or how about this: the World Trade Center is taller than University Hall. "Being taller than" is a relation between the two buildings. And we can say that that relation has being as well. It exists.
Relations are like properties in that both of them are supposed to be abstract. Now let me explain what that means. Something is abstract if it does not exist in any particular place, but instances, or members, of it can exist in many different places. For example, lots of different things have the property of redness: lots of things are red. And we find the relation "sitting on" all over the place: lots of things sit on other things. So the property, redness, and the relation, sitting-on, do not exist in any one particular place. So if we want to say that properties and relations are, or have being, clearly we want to say they have a different sort of being from the sort of being that physical objects, like rocks and trees, have. So thatís where this word "abstract" comes in. We apply the word "abstract" to properties and relations to mark the fact that if they exist, they donít exist in space or time, but that instances of them can exist in many different places. Redness itself is not supposed to exist anywhere, but our apple is red, and lots of roses are red; and thatís why we say that redness itself, as opposed to instances of redness, is abstract.
On the other hand the apple, and an individual rose, are said to be concrete. This means basically that they arenít abstract: they are particular individuals, located at a place and a time. So if you want a definition, to say that something is concrete is to say that it is a particular individual that is located at a particular place and time.
Iíve just explained the difference between abstract and concrete. Many philosophers say that properties and relations have an abstract existence, and that physical objects have a concrete existence. So now consider, arenít those two different ways in which a thing can be said to "be," or to have being, or to exist? I think you can see that "being" is an ambiguous word. We have found two examples of different senses of the words "being" or "existence."
Letís get back to the question of what "ontology" means. I said it was, in the words of Aristotle, "the science of being qua being." Well, the word "qua" means "with regard to the aspect of." So ontology is the science of being with regard to the aspect of being -- so itís the study of beings insofar as they exist. Ontology is concerned with the different senses of "being," or in yet other words, with the different fundamental categories of beings and the ways in which the things in the things in those categories can be said to exist. So from this we can derive some examples of ontological questions. First: what does it mean to say a physical object exists? Second: what sorts of beings are physical objects anyway? Third: what sorts of beings are an objectís properties or relations? And fourth: when does an object go out of existence, as opposed to merely changing?
In fact, those are exactly the four questions we are going to try to answer in the rest of our consideration of metaphysics. If youíre baffled about what these questions are asking, donít worry -- after we focus on each question individually you will be less confused.