Metaphysics is a broad area of philosophy marked out by two types of inquiry. The first aims to be the most general investigation possible into the nature of reality: are there principles applying to everything that is real, to all that is? – if we abstract from the particular nature of existing things that which distinguishes them from each other, what can we know about them merely in virtue of the fact that they exist? The second type of inquiry seeks to uncover what is ultimately real, frequently offering answers in sharp contrast to our everyday experience of the world. Understood in terms of these two questions, metaphysics is very closely related to ontology, which is usually taken to involve both ‘what is existence (being)?’ and ‘what (fundamentally distinct) types of thing exist?’
The two questions are not the same, since someone quite unworried by the possibility that the world might really be otherwise than it appears (and therefore regarding the second investigation as a completely trivial one) might still be engaged by the question of whether there were any general truths applicable to all existing things. But although different, the questions are related: one might well expect a philosopher’s answer to the first to provide at least the underpinnings of their answer to the second. Aristotle proposed the first of these investigations. He called it ‘first philosophy’, sometimes also ‘the science of being’ (more-or-less what ‘ontology’ means); but at some point in antiquity his writings on the topic came to be known as the ‘metaphysics’ – from the Greek for ‘after natural things’, that is, what comes after the study of nature. This is as much as we know of the origin of the word. It would, however, be quite wrong to think of metaphysics as a uniquely ‘Western’ phenomenon. Classical Indian philosophy, and especially Buddhism, is also a very rich source.
Any attempt on either question will find itself using, and investigating, the concepts of being and existence. It will then be natural to ask whether there are any further, more detailed classifications under which everything real falls, and a positive answer to this question brings us to a doctrine of categories. The historical picture here is complex, however. The two main exponents of such a doctrine are Aristotle and Kant. In Aristotle’s case it is unclear whether he saw it as a doctrine about things and their basic properties or about language and its basic predicates; whereas Kant quite explicitly used his categories as features of our way of thinking, and so applied them only to things as they appear to us, not as they really or ultimately are. Following on from Kant, Hegel consciously gave his categories both roles, and arranged his answer to the other metaphysical question (about the true underlying nature of reality) so as to make this possible.
An early, extremely influential view about reality seen in the most general light is that it consists of things and their properties – individual things, often called particulars, and properties, often called universals, that can belong to many such individuals. Very closely allied to this notion of an individual is the concept of substance, that in which properties ‘inhere.’ This line of thought (which incidentally had a biological version in the concepts of individual creatures and their species) gave rise to one of the most famous metaphysical controversies: whether universals are real entities or not. In different ways, Plato and Aristotle had each held the affirmative view; nominalism is the general term for the various versions of the negative position.
The clash between realists and nominalists over universals can serve to illustrate a widespread feature of metaphysical debate. Whatever entities, forces and so on may be proposed, there will be a prima facie option between regarding them as real beings, genuine constituents of the world and, as it were, downgrading them to fictions or projections of our own ways of speaking and thinking. This was, broadly speaking, how nominalists wished to treat universals; comparable debates exist concerning causality, moral value and necessity and possibility – to name a few examples. Some have even proposed that the categories espoused in the Western tradition are reflections of the grammar of Indo- European languages, and have no further ontological status.
Wittgenstein famously wrote that the world is the totality of facts, not of things, so bringing to prominence another concept of the greatest generality. Presumably he had it in mind that exactly the same things, differently related to each other, could form very different worlds; so that it is not things but the states of affairs or facts they enter into which determine how things are. The apparent obviousness of the formula ‘if it is true that p then it is a fact that p’, makes it seem that facts are in one way or another closely related to truth – although it should be said that not every philosophical view of the nature of truth is a metaphysical one, since some see it as just a linguistic device and some as a reflection, not of how the world is, but of human needs and purposes.
Space and time, as well as being somewhat elusive in their own nature, are further obvious candidates for being features of everything that exists. But that is controversial, as the debate about the existence of abstract objects testifies. We commonly speak, at least, as if we thought that numbers exist, but not as if we thought that they have any spatiotemporal properties. Kant regarded his things-in-themselves as neither spatial nor temporal; and some have urged us to think of God in the same way. There are accounts of the mind which allow mental states to have temporal, but deny them spatial properties.
Be all this as it may, even if not literally everything, then virtually everything of which we have experience is in time. Temporality is therefore one of the phenomena that should be the subject of any investigation which aspires to maximum generality. Hence, so is change. And when we consider change, and ask the other typically metaphysical question about it (‘what is really going on when something changes?’) we find ourselves faced with two types of answer. One type would have it that a change is an alteration in the properties of some enduring thing. The other would deny any such entity, holding instead that what we really have is merely a sequence of states, a sequence which shows enough internal coherence to make upon us the impression of one continuing thing. The former will tend to promote ‘thing’ and ‘substance’ to the ranks of the most basic metaphysical categories; the latter will incline towards events and processes. It is here that questions about identity over time become acute, particularly in the special case of those continuants (or, perhaps, processes), which are persons.
Two major historical tendencies in metaphysics have been idealism and materialism, the former presenting reality as ultimately mental or spiritual, the latter regarding it as wholly material. In proposing a single ultimate principle both are monistic. They have not had the field entirely to themselves. A minor competitor has been neutral monism, which takes mind and matter to be different manifestations of something in itself neither one nor the other. More importantly, many metaphysical systems have been dualist, taking both to be fundamental, and neither to be a form of the other. Both traditions are ancient. In modern times idealism received its most intensive treatment in the nineteenth century; in the second half of the twentieth century, materialism has been in the ascendant. A doctrine is also found according to which all matter, without actually being mental in nature, has certain mental properties.
There is also metaphysics that arises in reference to particular subject matters, this being therefore metaphysical primarily with regard to the second question (what are things ultimately like? – or, what kinds of thing ultimately exist?) rather than the first. One of the most obvious cases, and historically the most prominent, is theology; we have already mentioned the philosophy of mind, the philosophy of mathematics and the theory of values. Less obviously, metaphysical issues also intrude on the philosophy of language and logic, as happens when it is suggested that any satisfactory theory of meaning will have to posit the existence of intensional entities, or that any meaningful language will have to mirror the structure of the world. The political theorist or social scientist who holds that successful explanation in the social sphere must proceed from properties of societies not reducible to properties of the individuals who make them up (thereby making a society an entity that is in a sense more basic than its members) raises a metaphysical issue. Metaphysics, as demarcated by the second question, can pop up anywhere.
The relationship with metaphysics is, however, particularly close in the case of science and the philosophy of science. Aristotle seems to have understood his ‘first philosophy’ as continuous with what is now called his physics, and indeed it can be said that the more fundamental branches of natural science are a kind of metaphysics as it is characterized here. For they are typically concerned with the discovery of laws and entities that are completely general, in the sense that everything is composed of entities and obeys laws. The differences are primarily epistemological ones, the balance of a priori considerations and empirical detail used by scientists and philosophers in supporting their respective ontological claims. The subject matter of these claims can even sometimes coincide: during the 1980s the reality of possible worlds other than the actual one was maintained by a number of writers for a variety of reasons, some of them recognizably ‘scientific’, some recognizably ‘philosophical.’ And whereas we find everywhere in metaphysics a debate over whether claims should be given a realist or an antirealist interpretation, in the philosophy of science we find a parallel controversy over the status of the entities featuring in scientific theories.
It is true that there has been considerable reluctance to acknowledge any such continuity. A principal source of this reluctance has been logical positivism, with its division of propositions into those which are empirically verifiable and meaningful, and those which are not so verifiable and are either analytic or meaningless, followed up by its equation of science with the former and metaphysics with the latter. When combined with the belief that analytic truths record nothing about the world, but only about linguistic convention, this yields a total rejection of all metaphysics – let alone of any continuity with science. But apart from the fact that this line of thought requires acceptance of the principle about meaninglessness, it also makes a dubious epistemological assumption: that what we call science never uses non-empirical arguments, and that what we regard as metaphysics never draws on empirical premises. Enemies of obscurantism need not commit themselves to any of this; they can recognize the continuity between science and metaphysics without robbing anyone of the vocabulary in which to be rude about the more extravagant, ill-evidenced, even barely meaningful forms which, in the view of some, metaphysics has sometimes taken.
Even the philosopher with a low opinion of the prospects for traditional metaphysics can believe that there is a general framework which we in fact use for thinking about reality, and can undertake to describe and explore it. This project, which can claim an illustrious ancestor in Kant, has in the twentieth century sometimes been called descriptive metaphysics, though what it inquires into are our most general patterns of thought, and the nature of things themselves only indirectly, if at all. Though quite compatible with a low estimate of traditional metaphysics as defined by our two primary questions, it does imply that there is a small but fairly stable core of human thought for it to investigate. Hence it collides with the view of those who deny that there is any such thing.
- Kim, J. and Sosa, E. (eds) (1995) A Companion to Metaphysics, Oxford: Blackwell.