What Is Metaphysics?
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What Is Metaphysics?
Since we are seeking this knowledge, we must inquire of what kind are the causes and the principles, the knowledge of which is Wisdom.
Aristotle, Metaphysics 982A5
What can be seen is temporary, but what cannot be seen is eternal.
That all depends upon what the meaning of “is” is.
William Jefferson Clinton
1—Introduction
Metaphysics has a public relations problem. When some people hear the word they are likely to think of a certain area of the bookstore at the mall where you get books on the New Age movement, astral projection, and eastern herbal cooking! Others are likely to think of metaphysics as pure intellectual speculation about a subject where science cannot give us an answer to our questions. However popular, neither of these opinions is accurate. Metaphysics has a long, distinguished history, boasting some of the greatest thinkers of all time: Plato, Aristotle, Augustine, Boethius, Aquinas, Descartes, Leibniz, Locke, and many others. Along with logic and epistemology, metaphysics is the most basic part of philosophy. And metaphysics has been the long-standing friend of theology. The early creeds of Christendom are filled with metaphysical terms—person, essence, substance, subsistence—and they give testimony to the help that metaphysics can give to the development of systematic theology.
The term metaphysics was first used as a title for a group of works by Aristotle (384–322 BC). One set of his writings was about “the things of nature” and came to be called the Physics. Another set of works (which Aristotle himself never named) was called “the books after the Physics” (ta meta ta physica) by some ancient editors that collected and edited his writings in the first century BC. Thus metaphysics originally meant “after the Physics” and, while metaphysical reflection existed before Aristotle, the title was first used in the way just mentioned, and it has continued to refer to a certain branch of philosophy ever since.
It is difficult, if not impossible, to come up with an adequate definition of metaphysics. Usually, it is characterized as the philosophical study of the nature of being or reality and the ultimate categories or kinds of things that are real. This definition is adequate to capture much of what is done in metaphysics. Typical metaphysical questions are these: What is the difference between existing and not-existing? Is reality one or many? Are there abstract objects that exist but are not spatial and temporal? Are there substances and, if so, what are they? Are we free or determined? Is matter real and, if so, what is it? Do humans have minds as well as bodies? Is the property of being red real and, if so, what is it? Where is it?
A metaphysical problem is usually a puzzle about some ultimate kind of issue expressed in a question like one of the following:
Examples of (1) include, how could there be living things, given that everything in the universe is matter? How could values exist, given that everything that exists must exist at some point in space and time? Examples of (2) include, how could there fail to be abstract objects called numbers, given that statements of arithmetic (2 + 4 = 6) are necessarily true? How could there fail to be a soul, given the existence of freedom of the will?
These questions should give the reader a feel for the kinds of problems that metaphysicians address. In the remainder of this chapter, we will look at the main branches of metaphysics and survey some general guidelines often used in metaphysical investigation. The final pages of the chapter will look briefly at a major debate in metaphysics in order to illustrate a type of metaphysical dispute that has been around since at least the time of Plato: the debate between naturalists and ontologists about the existence of abstract entities (e.g., properties, numbers, propositions, sets, relations).
2—Main Branches of Metaphysics
Metaphysics is the philosophical study of being or reality. To help clarify this issue, consider the following sentences:
Each of these sentences uses a different sense of the word is. Part of metaphysical investigation is the task of distinguishing these different senses and saying something helpful about each one of them. Sentence (1) uses an is of being or existence. It asserts that Socrates exists. This sense of “to be” raises the question, what is it to exist or not exist? What is it about something that accounts for its existence? Sentence (2) uses an is of identity. It says that Socrates is identical to, is the very same thing as, the teacher of Plato. This raises another question: What does it mean for some thing x and some thing y to be the same thing? What is it for something to be identical to itself and different from everything else?
Sentence (3) employs an is of essential predication. It says that being human is the very essence of Socrates. This raises the question, what does it mean to say that something (being human) is the essence of something else (Socrates)? Do things really have essences and, if so, what are they? Sentence (4) contains an is of accidental predication. It says that Socrates has a property, being white, that is “present in” him. This raises the question of whether properties exist and, if so, what are they? Is there a distinction between essential and accidental properties? Does humanness relate to Socrates in a way different from the way whiteness relates to Socrates? Finally, sentence (5) uses an is of constitution, sometimes called a part-whole is. It says that Socrates is a whole with skin and bones as parts. Socrates is constituted by these parts. This raises the question of whether parts are different from properties. Can something lose parts and still be the same thing?
These five sentences and the questions they surface form the most basic area of metaphysical investigation. Philosophers have reflected on them for some time, and their reflections have led to some widely accepted subbranches of metaphysics. The main two divisions of metaphysics are general ontology (sometimes simply called ontology) and special metaphysics. Let us look at these in order.
2.1 General Ontology
General ontology is the most basic aspect of metaphysics, and there are three main tasks that make up this branch of metaphysical study. First, general ontology focuses on the nature of existence itself. What is it to be or exist? Is existence a property that something has? Does nothingness itself exist in some sense? Is there a sense of being such that fictional objects like the winged horse Pegasus have being even though they do not exist? The nature of existence will be part of the focus of chapter nine.
Second, in general ontology we study general principles of being, general features that are true of all things whatsoever. Medieval philosophers used the term transcendentals to stand for all those features that characterize all the different kinds of entities that exist. The notions of existence, unity, truth, and goodness have been taken by some to be examples of a transcendental. Everything that is, say a carbon atom, a person, a number, or the property of being green, is such that it exists, is a unity (i.e., is one entity in some sense), and is true and good. In chapter nine, we will investigate one such feature of reality—the nature of identity. Everything whatever is identical to itself and different from everything else. The study of the nature of identity can be classified as part of general ontology in that identity is a transcendental feature of all entities that exist.
Third, general ontology includes what is called categorial analysis. It is possible to classify or group things that exist in various ways ranging from very specific to very broad types of classification. For example, consider a light brown dog, Spot, standing to the left of a desk. The dog itself can be classified in broader and broader ways according to the following scheme: an individual dog, a mammal, an animal, a living thing, a substance. The color of the dog can be classified in this way: light brown, brown, a visible property, a property. The relationship between Spot and the desk can be grouped as follows: to the left of, a spatial relation, a relation.
In the example just mentioned, the ultimate categories used are those of substance, property, and relation. A set of categories is a collection of the ultimate, broadest classifications of all existent entities whatsoever such that (1) each entity will fit into a specific category and (2) the categories taken as a group will allow us to classify all entities. A set of categories is a set of mutually exclusive and exhaustive classifications of all entities. A set of categories is mutually exclusive in that a given category will have a distinguishing feature that sets entities in that category off and makes them distinct from the entities in the other categories. A set of categories is exhaustive in that all entities (except the transcendentals) will fit into one of the categories.
Note that the example of Spot includes higher and higher groupings that are more and more inclusive. For example, as one goes from light brown to brown to visible property to property, one goes from a less inclusive classification to a broader, more inclusive or more general classification. Sometimes the relationship between a higher, broader and a lower, more specific classification is called a genus-species relationship. Here are some examples of genus-species relationships: being a visible property or being brown; being a shape or being a square; being a sound or being the note C; being a spatial relation or being on-top-of.
In each case, the genus is broader than the species. In fact, a traditional way of viewing the genus-species distinction (going back to Aristotle) takes the species as a way that the genus can exist. There can be an example of a genus without a particular species (e.g., some entity can be a visible property without being brown, say, by being the property green), but there cannot be a case of a particular species without the genus above it being present as well (e.g., if Spot has the property of being brown, Spot also has the property of being a visible property).
One of the tasks of general ontology is to formulate a categorial classification of reality and study the features of each ultimate category that make it unique. In general ontology, we also study the various genera and species that form the hierarchy of classification within each ultimate category. A set of categories of being can be very useful in clarifying and helping to solve various philosophical problems.
For example, many philosophers have noted that a distinguishing mark of the mind is intentionality. Roughly, intentionality is the ofness or aboutness of the mind. For every mental state (e.g., a state of hoping, thinking, believing, fearing, wishing), that state is always a state of or about something beyond it (and this is true even if the object of the mental state does not exist, say, when someone has a fear of Zeus). An interesting and very important question we can ask about intentionality is this: Is intentionality a property or a relation? This question focuses attention on how we should understand and classify intentionality itself. In chapter ten, we will look at two important categories of being: substance and property.
In the history of philosophy, there have been various opinions about the nature of categories, that is, about what a set of categories amounts to. However, two main schools of thought about categories are represented by Aristotle and Immanuel Kant. According to Aristotle, there are ten basic categories of reality: substance, quantity, quality, relation, place, time, posture, state, action, and passivity. These ten categories for Aristotle can, in turn, be understood as taking the category of substance as fundamental or basic and the other nine categories as different ways that a substance can be modified or qualified. For example, the substance Spot can be twenty-five pounds, brown, and so forth.
What is most crucial for Aristotle’s view of the categories, however, is not the precise nature or number of his classifications. Rather, the thing of central importance in Aristotle’s approach to the categories is that he took them to give us real divisions in the actual world itself as it exists “out there,” that is, as it is in itself independent of human thought or language. For him, the categories are the broadest, real divisions of being.
For Kant, the categories (he lists twelve of them in The Critique of Pure Reason) are not divisions of the world as it is in itself (he called this the noumenal world), but rather they express the divisions of the world as it appears to us as knowing subjects (he called this the phenomenal world). Thus Kant’s categories express the different ways that knowing subjects organize and classify the world of their sensory experience. A Kantian category is a broadest division of the phenomenal world, the sensory world as it is experienced by us. Thus, according to Kant, a study of the categories does not tell us about real divisions in the world as it is in itself. Rather, it gives us insight about how we as sensing and knowing subjects must divide the world of sensory experience to make it knowable to us.
We cannot enter into the debate here as to which view of the categories is correct. Part of this debate involves issues in epistemology, especially skepticism, the nature of perception, and the adequacy of postmodernism and various forms of deconstructionism. Some of these issues were taken up in part two of this text. Suffice it to say here that we think that the best philosophical arguments, as well as the most reasonable way to understand Christian theology, imply that Kant was wrong about the categories. Whether or not we are right in this understanding, we will, nevertheless, approach our study of some categories in the next few chapters in a way that sides with the spirit of Aristotle’s views: we will take the discussed categories to be real categories of the external world as it is in itself.
In addition to the debate about how to understand what the categories themselves are, there has been a division of opinion about the exact identity and number of the ultimate categories of being. Aristotle thought there were ten ultimate categories, with the category of substance being most basic. Others—for example, process philosophers—hold to a different set of categories, with the category “event” being most basic. Still other philosophers have listed various other categories as necessary to make sense of reality. As already mentioned, we will look at only two categories: substance and property. But one should remember that some philosophers reject these categories while others accept but add additional categories to them.
2.2 Special Metaphysics
Besides general ontology, a second area of study in metaphysics is called special metaphysics. In special metaphysics, two different types of concerns are in view. First, there is the study of specific topics of special interest: Is there a soul or mind? Are humans free or determined? Is there such a thing as personal identity, that is, do persons remain the same through change or are persons best viewed as a series of events called person-stages? Is there such a thing as causation?
Second, there is the second-order metaphysical clarification and investigation of other fields of study, for example, sociology, biology, physics, and psychology. Here, the metaphysician asks questions like, Are there electrons and, if so, what are they? Do social groups exist as wholes that are “more than” the sum of their parts? And so on. It should be clear that there is an order between general ontology and special metaphysics. The problems of special metaphysics should be tackled after work has been done in general ontology. In light of the positions one adopts in general ontology, one will have more conceptual tools to employ in working on the topics in special metaphysics. For example, if someone says that a carbon atom is a substance, the insights of general ontology will help to clarify how this should or should not be understood. In chapters eleven through fourteen, we will investigate certain issues in special metaphysics after we have looked at problems in general ontology in chapters nine and ten.
3—Methods of Approach in Metaphysics
When we do metaphysical investigation, how should we proceed? What methodology should we employ? Unfortunately, there is no general agreement among philosophers about how to answer these questions, and in fact, one’s view about methodology in metaphysics will be dependent, at least in part, on one’s positions about general solutions to philosophical questions.
For example, some philosophers are philosophical naturalists who hold that reality is exhausted by the spatiotemporal world of physical objects embraced by our best scientific theories. In their view, science is the main approach to investigating the world, not philosophy. Many who embrace this sort of naturalism see the role of metaphysics to be that of clarifying our use of language, especially our use of scientific language. The methodology of the metaphysician is to take scientific theories, analyze and clarify the use of metaphysical terms within those theories, and formulate a worldview built on those theories. Metaphysics is not the study of reality—science is—but rather of our talk, especially scientific talk of reality. On this view, linguistic analysis is the main tool of the philosopher engaged in metaphysics. He or she will analyze and clarify the scientist’s use of the terms substance and property in sentences like “carbon is a substance with such and such properties.”
Unfortunately, this approach is wrong-headed. It is a part of metaphysics to analyze and clarify our use of language, including scientific language. However, there is no good reason to limit metaphysical investigation in this way, especially when we realize that science presupposes philosophical and metaphysical doctrines (see chaps. 17–20). Thus metaphysics is conceptually prior to science, not vice versa. Science may offer help to metaphysics in various ways, but science cannot dictate to the metaphysician what he or she ought to believe about reality or about the methods to be used in metaphysics. Moreover, language (including scientific language) itself exists. Therefore, metaphysics cannot be reduced to language because language itself is part of metaphysical study.
In spite of the fact that there are no generally accepted methods of approach in metaphysics, it is still possible to state some general guidelines that should be followed in metaphysics unless there is good reason to set them aside. Here are some of them:
1. Metaphysical study should begin with and take into account the things we already know or have reason to believe are true before we begin doing metaphysics. Metaphysics is rooted in wonder and puzzlement about what we know or have reason to believe, and it is an attempt to analyze, clarify, and account for those items of knowledge and rational belief. There are at least four sources of these beliefs. First, metaphysics focuses on what we know from the critical use of common sense. By this we mean that our common sense beliefs, when we are “critical” of them in the sense of being aware of them, reflecting carefully about them, seeing if they make sense and stand up to scrutiny, provide material for metaphysical study. For example, it would seem to be an item of critical common sense that an apple is both red and sweet. The redness of the apple is real, is different from the sweetness of the apple, and is the color of the apple’s surface. Metaphysics tries to account for this item of common sense. Critical common sense can, of course, be wrong, but it should be trusted unless there is good reason to abandon it. The burden of proof works on behalf of critical common sense, not against it for at least three reasons. For one thing, we simply do, in fact, know many of the things critical common sense offers us. Moreover, much of the point of metaphysics is rooted in wonder and puzzlement over the things we have reason to believe in critical common sense. Finally, Christian theism implies that, generally, we can trust our various faculties to give us true, rational beliefs, and these beliefs are part of the core of common sense. To the degree that some idea of common sense can be shown to be a result of cultural indoctrination, to that degree it is suspect (though, of course, it could still be true). But many of the beliefs of common sense that generate metaphysical speculation (like the apple example above) are not like this.
Second, we should use our knowledge from Christianity to help us do metaphysics in at least three ways. First, certain truths in theology require metaphysical study to help clarify them. The doctrine of the Trinity illustrates this. Second, truths from Christianity can be used as background knowledge to guide us in rejecting certain metaphysical positions and in seeking further, independent reasons for that rejection. If we take physicalism to be the view that a human being is simply a material object, nothing more and nothing less, then the Old and New Testament teaching about the soul, understood in the most natural way exegetically and in keeping with the history of the church, will lead us to reject physicalism as false and unreasonable, and we will do metaphysics to find further, independent reasons for our understanding of the Christian view. This can, of course, be abused. So we need to be careful that we have understood Christian teaching on the issue carefully and with a sense of integrity regarding genuine options within orthodox theology. But theology is still an important source of propositions for doing metaphysics. Third, Christian theology can remove certain intellectual barriers that force some thinkers to adopt positions in metaphysics in a one-sided way. In these cases, the Christian philosopher can be more open than his or her secular counterpart to seeing both sides of a dispute. For example, philosophers who hold to physicalism as a metaphysical worldview cannot embrace the existence of abstract objects (nonphysical entities that do not exist in space or time) such as numbers because they are not material. The Christian philosopher can be open to embracing the existence of numbers as abstract objects or to rejecting them since he or she is not forced to do metaphysics in light of physicalism. On the other hand, Christian teaching can introduce metaphysical problems of its own. For example, if abstract objects like numbers exist, then since they are neither in time nor space, they did not come into being at a moment of time. This means that they were not created in the same way that trees and rivers were created, so the Christian philosopher who embraces abstract entities must harmonize their existence with the doctrine of God as creator of everything.
In addition to critical common sense and Christian teaching, our knowledge of our own self is a third important source of information for metaphysics. A careful description of our awareness of our own selves, for instance, that we seem to be continuing, enduring beings who are distinct from the rest of the world (one’s desk is not part of oneself), that we are conscious, make decisions, have beliefs and sensory experiences, could (at least) possibly survive the death of our bodies and so forth, can give us insights into metaphysics. Any broad metaphysical system must take into account what we have reason to believe about our own selves.
A final source of beliefs for metaphysical reflection is reliable information from other fields of study. If a business professor claims that corporations have moral responsibility, does this mean that corporations exist? If the self can “split” in brain operations or in cases of multiple personality, can we still make sense of the soul as a unified entity? If living organisms evolved, can we still believe that they have natures? In cases like these, other disciplines provide material for metaphysical study. Keep in mind, however, that questions like these are primarily metaphysical questions, not primarily questions of neurophysiology and so forth. Attempts to answer them will require careful treatment from philosophers trained in metaphysics who try to give genuine attention to the real facts present in other fields of study. Metaphysics is concerned with the facts. But more importantly, it is the distinctive concern of metaphysics that we correctly interpret those facts in a philosophical way.
2. State the metaphysical problem you are trying to solve and what gives rise to the problem. For example, two roses seem to have the very same smell. The problem becomes this: How can each rose have the same smell? Does that mean that the specific smell is in both roses at the same time? How can something be in more than one thing at once? On the other hand, if each rose has its own smell, how are we to account for the fact that the smell seems to be the same in both roses? If we say that the smell of one rose exactly resembles the smell of the other, doesn’t this just mean that the roses resemble each other in that they have the same smell (since they do not resemble each other, say, in color or shape)?
After the problem is stated, list the different metaphysical alternatives to the problem, along with the assumptions made by each alternative, draw the implications of each alternative, and see which is most reasonable. In the example about the roses, two alternatives would be that the roses have the same smell or that each has its own smell exactly resembling the smell of the other. The assumption of the first alternative is that properties like a specific rosy smell can be in more than one thing at once and the second alternative denies this. In any metaphysical study, it is important to state the implications that follow from either accepting or denying that something is real. In Plato’s dialogue Parmenides 136a, Plato reminds us through the lips of Parmenides, “If you want to be thoroughly exercised, you must not merely make the supposition that such and such a thing is and then consider the consequences; you must also take the supposition that the same thing is not.” If we deny that properties, truth, God, freedom, the soul, or other entities are real, what follows from this denial? What follows from embracing their reality?
3. Use thought experiments as sources for counterexamples to metaphysical arguments. In metaphysics, we are primarily interested in what something must be, not in what it merely happens to be by accident. For example, the number two must be even, but it happens to be Uncle Larry’s favorite number. Again, all individual human beings necessarily have the property of being human, but they also all happen to have the property of being born on earth. In each case (being even and being human), the former information is more central to metaphysics than the latter. Metaphysical study seeks to uncover what numbers, causation, minds, values, properties, and so forth must be. What is their very nature and essence?
This aspect about metaphysics leads to an insight about the role of thought experiments as sources of counterexamples for assessing metaphysical claims. To understand this insight, we need to introduce the notion of something called a possible world. When some philosophers talk about the existence of various possible worlds, they mean to describe alternative parallel universes that are all equally real. This is not what we mean by a possible world. Our use of the notion of a possible world can be clarified as follows. The actual world, the real world of all and only entities that exist, can be described by a conjunction of all and only true propositions. For example, the proposition There are goats in Virginia is a proposition truly describing the actual world, but There are unicorns in Nebraska does not. The actual world is the world God really created (it also includes God himself). An impossible world is a world that cannot exist; the conjunction of propositions describing it includes a logically impossible proposition. Such a world is one that God could not make. No conceivable set of circumstances could exist to make such a world a reality. For example, a world with square circles in Missouri is an impossible world. A possible world is a world whose description does not include a logically impossible proposition. A possible world is a world that God could create; it is a world that could have existed even though it may not. For example, a world with unicorns in California is not the actual world (we hope!), but it is a possible world.
Now, in metaphysics, a philosopher will often argue that some entity P is really nothing but Q. For example, heat is really nothing but the motion of molecules, the mind is really nothing but the brain, the color red is really nothing but the word red being used of an object or, perhaps, red is just a certain wavelength of light. At other times, a philosopher will argue that C is the very essence of D, that is, that D could not exist without C existing and being the very nature of what D is. For example, some have claimed that the very essence of the number two is to be the smallest even number greater than one, the nature of squareness is to be a shape, the essence of being a person is to be a material object, and the essence of existing is to be located at a place in space and time.
In each of the examples cited, we can test the proposal it illustrates by using a thought experiment to suggest a counterexample that runs contrary to the proposal in question. These thought experiments can be seen as attempts to state a possible world where one can have P but not Q or Q but not P. For example, if there is a possible world where there are minds without brains (say in a disembodied form of existence) or brains without minds (a zombie world), then the proposal that minds are nothing but brains is false. Furthermore, if C is offered as the very nature of D, then in every world where D exists, C must exist also. If we can state a possible world where D exists without C, then C cannot be taken to be the essence of D. If C is “Uncle Larry’s favorite number” and D is the number two, then there could be a world where D (the number two) exists but C does not (in worlds where Uncle Larry is dead or hates the number two). This possible world is a counterexample to the proposal in question.
4. In metaphysics, as with other forms in knowledge generally, we are not constrained to operate within the bounds of sense experience. Advocates of strong forms of empiricism claim that all knowledge is limited to what can be directly or indirectly tested by sensory experiences from the five senses. Advocates of strong forms of empiricism have never been fond of metaphysics and for good reason. There is almost no issue of interest in metaphysics whose solution can be stated or substantiated solely within the confines of strong empiricism. The conclusion to draw from this is not that metaphysics is an illusion or mere speculation, but rather that strong empiricism is an inadequate epistemology for accounting for what we can know in general, especially for metaphysical knowledge.
Not only is it unduly confining to limit what we can know in metaphysics or elsewhere to the bounds of sensory experience, it is also a hindrance to the development of faith. In The Screwtape Letters, C. S. Lewis has the demon Screwtape remind his “junior tempter” Wormwood about how to keep his human “patient” from becoming a Christian. Screwtape warns Wormwood not to argue with the patient because reasoning moves the discussion onto territory where the Enemy (God) can operate too. Says Screwtape,
By the very act of arguing, you awaken the patient’s reason; and once it is awake, who can foresee the result? Even if a particular train of thought can be twisted so as to end in our favour, you will find that you have been strengthening in your patient the fatal habit of attending to universal issues and withdrawing his attention from the stream of immediate sense experiences. Your business is to fix his attention on the stream. Teach him to call it “real life” and don’t let him ask what he means by “real.”
Lewis’s remarks here provide an occasion to point out that metaphysical study—which includes “the fatal habit of attending to universal issues”—can be a real aid to Christian growth for a number of reasons, not the least of which is that it helps the intellect form habits that free it from grasping only issues and truths within the boundary of sensation.
In this chapter, we have looked at the main branches of metaphysics and surveyed some guidelines useful for metaphysical study. We can gain a further sense of what metaphysics is by briefly looking at a major metaphysical controversy that has been around since the time of Plato (428–348 BC).
4—The Dispute Between Naturalists and Ontologists
In one of Plato’s last dialogues, he describes a metaphysical debate that was raging during his own day. In Sophist 246a-c we read:
Stranger: What we shall see is something like a battle of gods and giants going on between them over their quarrel about reality.
Theaetetus: How so?
Stranger: One party is trying to drag everything down to earth out of heaven and the unseen, literally grasping rocks and trees in their hands, for they lay hold upon every stock and stone and strenuously affirm that real existence belongs only to that which can be handled and offers resistance to the touch. They define reality as the same thing as body, and as soon as one of the opposite party asserts that anything without a body is real, they are utterly contemptuous and will not listen to another word.
Theaetetus: The people you describe are certainly a formidable crew. I have met quite a number of them before now.
Stranger: Yes, and accordingly their adversaries are very wary in defending their position somewhere in the heights of the unseen, maintaining with all their force that true reality consists in certain intelligible and bodiless forms. In the clash of argument they shatter and pulverize those bodies which their opponents wield, and what those others allege to be true reality they call, not real being but a sort of moving process of becoming. On this issue an interminable battle is always going on between two camps.
In this text, Plato makes reference to a metaphysical dispute that, to put it in contemporary terms, centers on the existence of abstract entities. We cannot investigate the details of this debate here—some aspects of the dialogue will be covered in chapter ten. For now, it will help to clarify the nature of metaphysical issues and positions if we state what this debate is about and what the major options have been regarding it. Let us define the universe as the total spatiotemporal system of matter and (impersonal) energy, that is, as the sum total of material objects, in some way accessible to the senses and to scientific investigation. The universe consists of individual things, events, and processes that exist within space and time, for example, atoms, rocks, rivers, osmosis, and flashes of lightning. For any entity in the universe, it is appropriate to ask where and when it is.
In addition to the universe, many philosophers have, like Plato, believed in another realm of entities that are called abstract objects. Abstract objects are immaterial (i.e., nonphysical) entities that do not exist inside space and time; instead, they are timeless and spaceless. It makes no sense to ask where or when they exist.
There have been many examples of abstract entities: properties, relations, sets, numbers, and propositions. On this view, properties are entities that can be exemplified by many things at the same time (e.g., redness, goodness, triangularity, humanness) and relations are entities that can relate two or more things and can be in more than one group of things at the same time (e.g., brighter than, father of, larger than). Properties and relations are called universals because, as was mentioned, they can be in more than one thing at once or can relate more than one group at once. Several apples can have the same color of red and several groups of people can enter into the “father of” relation.
A set is a group or collection of things called the members of the set. The set of all numbers from one to ten is an example of a set. Numbers are the things that enter into certain mathematical relationships, for example, addition, subtraction. Propositions are the contents expressed in declarative sentences and contained in people’s minds when they are thinking. Propositions are also the things that are either true or false and that can be related to each other by means of the laws of logic (e.g., “if, then,” “if and only if”).
Let us call the world the sum total of everything whatever that exists including nonspatiotemporal abstract entities as well as the spatiotemporal universe of physical entities. The metaphysical debate alluded to by Plato can now be put as follows: Do abstract entities exist? Or put another way: Does the world exist or is there only a universe? Ontologists are those philosophers who, like Plato, believe in the world and abstract entities. The term naturalism has many different meanings, but a standard use of the term defines it as the view that the universe alone exists. Since most current forms of naturalism are physicalist in flavor, naturalism has come to mean that reality is exhausted by the spatiotemporal world of physical objects accessible in some way to the senses and embraced by our best scientific theories. The naturalist has three tasks before he or she can defend naturalism as a broad metaphysical view:
The debate between ontologists and naturalists is a clear example of a metaphysical dispute. We mention it here only as an illustration of metaphysics and not as an occasion to journey into the nuances of the dispute. However, proposition (1) will be discussed in chapters eleven through fourteen and to a lesser degree in chapters fifteen and sixteen. Propositions (2) and (3) (especially 2) will be a major center of focus in chapter ten. However, before we can look at these issues, a more fundamental set of metaphysical notions should be clarified (see chap. 9): the nature of existence, identity, and reductionism. To these issues we now turn.
Chapter Summary
The term metaphysics was first used as a title for a group of works by Aristotle. Roughly, it is the philosophical study of the nature of being or reality and the ultimate categories or kinds of things that are real. The two main divisions of metaphysics are general ontology (sometimes called ontology) and special metaphysics. There are three main tasks in general ontology: (1) to understand the nature of existence itself and the difference between existing and not existing; (2) to study general principles of being (transcendentals) true of all things whatsoever; (3) to give a set of exhaustive, mutually exclusive categories that are the ultimate, broadest classification of all entities whatever. Aristotle took categories to be real divisions of the external world; Kant took them to be divisions of how we as knowing subjects organize the phenomenal world. Special metaphysics focuses on (1) specific topics of special interest (e.g., are we free or determined?) and (2) the metaphysical clarification of other fields of study.
There is no agreed on method for doing metaphysics. However, the following principles are helpful guidelines for metaphysical investigation: (1) Metaphysics must take into account what we already know or have reason to believe prior to doing metaphysics. (2) The metaphysician should state a problem clearly, along with alternative solutions and the facts and assumptions used in each one, draw the implications of each solution, and see which is most reasonable. (3) In metaphysics we can use possible worlds to state thought experiments that serve as counterexamples to metaphysical claims. (4) In metaphysics, we need not operate within the bounds of crude empiricism.
The debate between naturalists and ontologists over the existence of the world and abstract entities is a good example of a metaphysical dispute.
Checklist of Basic Terms and Concepts
abstract entities
accidental predication
actual world
being
categorial analysis
categories
constitution
essence
essential predication
extreme nominalism
general ontology
genus-species relationship
identity
impossible world
impure realism
intentionality
naturalism
naturalists
nominalism
noumenal world
numbers
ontologists
ontology
part-whole
phenomenal world
possible world
process philosophers
properties
propositions
relations
sets
special metaphysics
thought experiments
transcendentals
universals
universe
world