Metaphysics

What it asks

Metaphysics asks what there is. Not what things are made of, which is physics, but what KINDS of thing there are and what it takes to be one. Tables and electrons are uncontroversial. Numbers, laws of nature, minds, holes, possibilities, the future, the average taxpayer and the number seven are not.

The second question is harder and comes with the first. Even where two people agree that something exists, they may disagree completely about what its existing consists in. A shadow exists, but not in the way the wall does. A debt exists, but you cannot find one. Working out what those differences amount to is the whole business of the branch.

The recurring problems

Universals and particulars. Two apples are both red. Is there one thing, redness, that both have, or are there only the two apples and a habit we have of grouping them? This is the oldest live dispute in the subject and it has not moved much since the twelfth century.

Identity through change. A thing persists while its parts, properties and location all change. What, if anything, stays the same? The question is easy to state, and every answer to it has consequences someone finds unacceptable.

Possibility. Some things could have been otherwise and some could not. Water could have been undiscovered; water could not have failed to be H2O. That distinction is enormously useful and no one agrees what makes it true.

Whether the question is answerable. Metaphysics is the one branch with a serious tradition of denying that it has a subject at all. That objection is treated as one of its problems rather than as an attack from outside.

How it developed

Aristotle called it first philosophy and defined it as the study of being as such, rather than of any particular kind of being. The medieval schools made it the framework everything else was stated in, and worked the problem of universals to a level of precision that was not matched again for six hundred years.

The seventeenth century built systems. Descartes, Spinoza and Leibniz each produced a complete account of what exists, deduced from a small number of starting points, and each account contradicted the others.

Kant's response in 1781 was the turning point and it was hostile. The mind, he argued, cannot get outside its own conditions of experience to check them against reality, so the traditional questions are not merely unanswered but unanswerable. Metaphysics after Kant has largely been an argument about how much of that verdict to accept.

The logical positivists accepted all of it and went further, holding that metaphysical claims are not false but meaningless, since nothing would count as testing them. For twenty years the branch was close to abandoned in English-speaking philosophy. Quine's On What There Is in 1948 reopened it by asking a narrow, answerable version of the question - what a theory commits you to - and Kripke's Naming and Necessity in 1980 brought back essence and necessity, which the positivists had thought disposed of for good.

The positions within it

The rival answers here belong to the Schools section. Realism and nominalism divide over universals. Substance theory and bundle theory divide over what a thing is apart from its properties. Presentism and eternalism divide over whether the past and future exist. Materialism, idealism and dualism divide over what the world is ultimately made of.

Each of those is an answer given inside this branch, not an alternative to it.

Where it stands now

Analytic metaphysics is active and technical, and it is also under sustained internal attack. The complaint is that its disputes are verbal - that realists and nominalists are not disagreeing about the world but using the word exists differently - and that has produced a whole sub-field, meta-metaphysics, asking whether the questions are substantive.

The other current pressure is from physics. Space, time, causation and identity are all treated by physical theory, and philosophers who take that seriously argue that armchair metaphysics has been describing a world that turned out not to be ours.