What Is Metaphysics?
The great Greek philosopher Plato wrote (in the dialogue Theaetetus ) that philosophy "begins in wonder," a phrase repeated by his student Aristotle in his Metaphysics . This is especially true of that branch of philosophy that we, echoing the title of Aristotle's book, call "metaphysics." In metaphysics we puzzle and wonder about what exists and what existing things are like, in their most fundamental features and interrelationships.
1.1 The Subject of Metaphysics
The first part of metaphysics is known as "ontology," the study of what there is. In ontology we attempt to give, in broad outlines, an inventory of reality. Are there particular things, such as cabbages, kings, quarks, and galaxies? How many such things are there? One? Many? Infinitely many?
Are there properties, ways things are? For example, is there, in addition to all the individual horses, the property of being a horse (equinity)? If so, how many such properties are there? Is there a property for every common noun and every adjective? A property of being red, of being ugly, of sleeping? Do some of these properties exist as separate universals ? That is, is one and the same property somehow shared by everything that has that property? If so, do each of these universals inhere within many particular things, or do they in some other way explain the similarities and common characteristics of those many particular things? And are there relations , like that of being more massive than or being the same color as, that hold between or among two or more things?
Are there things that could be called "facts" or "states of affairs," such as the fact that water molecules contain hydrogen or the state of affairs of all native mammals in Australia's being marsupials? Are there negative facts, such as the fact that there is no plant life on the sun? If there are facts, are they the things that, by simply existing, are responsible for making certain beliefs and statements true? Is truth itself a property, and if so, of what things? Do facts contain both particular things and universal properties? Are there merely possible facts, and if so, what are they like? What is the fundamental difference between merely possible facts and the actual ones?
Other parts of metaphysics constitute the study of the fundamental structure of reality as a whole. How do things fit together to make a world? Plato describes this task of philosophy "carving nature at the joints," comparing the metaphysics to a skillful and knowledgeable act of dissection. Here are four relations that seem to be among the fundamental relations of this worldly structure: the relation between things and their properties, between wholes and their parts, between causes and effects, and between things related to each other in space and in time. We will examine all of these foundational relations in some detail.
1.2 The Methods of Metaphysics
Since metaphysicians study reality in its most fundamental and general aspects, in doing it we must marshal as much evidence about the world as we possibly can. All of our knowledge of the world, whether innate or acquired through ordinary life or through specialized sciences, contributes data to the metaphysical theorist. So, too, do hunches and intuitions of the truth, when more secure knowledge is unavailable. The method of the metaphysician is a mixture of the testimony of pure reason, that which is prior to and independent of experience (the a priori ), and the testimony of experience itself (the a posteriori ), in all its breadth and variety. Metaphysics is in this way like most other sciences. (We use the word "science" here in a broad sense, as a label of any systematic field of knowledge.)
What exactly the methods of metaphysics should be is one of the most hotly disputed top