Metaphysics

1. General metaphysics

Any attempt on either question will find itself using, and investigating, the concepts of being and existence (see Being; 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 (see 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 (see Kant, I.). 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 (see Hegel, G.W.F.).

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 (see Particulars; Universals). Very closely allied to this notion of an individual is the concept of substance, that in which properties ‘inhere’ (see Substance). 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 (see Species; Natural kinds). 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 (see Nominalism).

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 (see Objectivity; Projectivism). This was, broadly speaking, how nominalists wished to treat universals; comparable debates exist concerning causality (see Causation), moral value (see Emotivism; Moral realism; Moral scepticism; Value, ontological status of) and necessity and possibility (see Necessary truth and convention) – to name a few examples. Some have even proposed that the categories (see above) espoused in the Western tradition are reflections of the grammar of Indo-European languages, and have no further ontological status (see Sapir-Whorf hypothesis).

Wittgenstein famously wrote that the world is the totality of facts, not of things, so bringing to prominence another concept of the greatest generality (see Facts). 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 (see Truth, coherence theory of; Truth, correspondence theory of) – 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 (see Truth, deflationary theories of) and some as a reflection, not of how the world is, but of human needs and purposes (see Truth, pragmatic theory of; Relativism).

Space and time, as well as being somewhat elusive in their own nature, are further obvious candidates for being features of everything that exists (see Space; Time). But that is controversial, as the debate about the existence of abstract objects testifies (see Abstract objects). We commonly speak, at least, as if we thought that numbers exist, but not as if we thought that they have any spatio-temporal properties (see Realism in the philosophy of mathematics). Kant regarded his things-in-themselves as neither spatial nor temporal; and some have urged us to think of God in the same way (see God, concepts of). There are accounts of the mind which allow mental states to have temporal, but deny them spatial properties (see Dualism).

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 (see 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 (see Continuants). 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 (see Momentariness, Buddhist doctrine of). 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 (see Events; 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 (see Identity; Persons; Personal identity).

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 (see Buddhism, Yogācāra school of; Idealism; Materialism; Materialism in the philosophy of mind; Monism, Indian; Phenomenalism). In proposing a single ultimate principle both are monistic (see Monism). 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 (see Neutral monism). More importantly, many metaphysical systems have been dualist, taking both to be fundamental, and neither to be a form of the other (see Sāṅkhya). Both traditions are ancient. In modern times idealism received its most intensive treatment in the nineteenth century (see Absolute, the; German idealism); 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 (see Panpsychism).