A History of Ontology

The questions in this section are old, and their history is not decoration. Most of the positions still defended were first stated by someone whose reasons are worth knowing, and several apparent innovations are recoveries. This page runs the thread from Parmenides to the present, keeping to arguments still in play rather than attempting a survey.

Ancient

Parmenides begins the subject with an argument rather than a doctrine. What is not cannot be thought or spoken of, since to think is to think something; therefore only what is can be thought; therefore change, which requires something to come from what is not, is impossible, and reality is one, unchanging, and undivided. The argument is bad, and identifying exactly where it goes wrong took two millennia — it conflates the "is" of predication, of identity, and of existence, distinctions not available to him. Its legacy is the problem of negative existentials and Plato's "beard."

Plato answers the one-over-many with the Forms: what many things share is a single entity, existing apart from them, in which they participate. The Parmenides contains his own best objection, the third man. The Forms are the origin of transcendent realism about universals and, by a different route, of mathematical platonism.

Aristotle supplies most of the vocabulary still in use. The Categories gives the first category scheme and makes primary substance basic; the Metaphysics adds hylomorphism and the thesis that being is said in many ways, with substance as the focal case — the ancestor of ontological pluralism. His realism about universals is immanent rather than transcendent: the form is in the thing.

Medieval

The medieval contribution is standardly reduced to the problem of universals, which undersells it, but that problem does frame the period. It reaches the Latin West through Boethius, translating Porphyry's three unanswered questions: do genera and species subsist or reside in the understanding; if they subsist, are they corporeal or incorporeal; and are they separate from sensibles or in them?

• Abelard develops an early non-realism: what is common is not a thing but a status, a way things are, since only individuals exist.
• Ockham gives nominalism its most rigorous form, with concepts as natural signs, and states the parsimony principle that bears his name.

Two other developments matter to this section:

• Avicenna's essence/existence distinction. What a thing is is separable in thought from that it is; essence is neutral as regards existence and universality. This is the ancestor of the essence tradition and, at a distance, of Meinong's independence of Sosein from Sein.
• Aquinas on esse. In creatures, essence and existence are really distinct and existence is received; in God alone they coincide. This makes existence something a thing has rather than a further property, and it is the background against which Kant's "existence is not a real predicate" is a rejection rather than a discovery.
• Duns Scotus contributes both haecceity — the individuating principle contracting a common nature to this individual, still the standard term in the individuation debate — and the univocity of being, against the analogists, on the ground that no inference from creatures to God is possible otherwise.

Early modern

Descartes reduces the categories to two created substances, distinguished by principal attributes, and generates the mind–body problem from the scheme itself. Spinoza takes the independence criterion for substance literally and concludes there is exactly one. Leibniz takes the unity criterion literally and concludes there are infinitely many simple ones, and formulates the Identity of Indiscernibles.

Locke distinguishes real from nominal essence — the underlying constitution versus the classificatory definition, which anticipates the natural kinds debate — and confesses that the substratum is "something, we know not what." Hume draws the conclusion: with no impression of substance, there is no idea of it, and a thing is a bundle of qualities.

Kant ends the tradition in its old form. Categories are not divisions of being but conditions of possible experience; ontology as a science of things in themselves is impossible, and its legitimate remnant is the analytic of the understanding. He also supplies the argument the modern treatment of existence begins from: existence is not a real predicate, and a hundred real thalers contain no more coin than a hundred possible ones.

The two twentieth centuries

After Kant the subject splits, and the two lines answer his negative claim in opposite ways. Running them as parallel tracks makes the structure visible:

The analytic line. Frege makes existence a second-order property expressed by the quantifier; Russell's theory of descriptions eliminates apparent reference to what does not exist; the Tractatus proposes an ontology of facts; Carnap concludes that external existence questions are pseudo-questions.

The phenomenological line. Brentano revives intentionality — every mental act is directed at an object — which makes the status of non-existent objects urgent. Meinong answers with objects beyond being. Husserl distinguishes formal from regional ontology. Heidegger charges the whole tradition with the forgetfulness of Being.

Where the tracks stop talking: Carnap's 1932 attack on Heidegger, which takes das Nichts selbst nichtet as the paradigm of a meaningless pseudo-statement. Note the shared premise — both traditions inherit Kant's denial that existence is a real predicate — and the opposite conclusions drawn from it. The contemporary reconvergence is ontological pluralism.

The Quinean revival and after

Quine's "On What There Is" (1948) restores ontology to respectability within the analytic tradition by making it tractable: a criterion of commitment, a method of paraphrase, and a naturalism that ties the whole to science. Strawson's Individuals (1959) adds descriptive metaphysics — describing the structure of our conceptual scheme rather than revising it — which licenses a great deal of subsequent work.

The boom follows: Goodman on nominalism and the calculus of individuals; Armstrong on universals, states of affairs, and laws; Lewis on modal realism, naturalness, and mereology; Kripke on necessity, rigid designation, and essence; van Inwagen on composition; Fine on essence and grounding.

Now. Three currents. Grounding and fundamentality have replaced supervenience as the tools for stating dependence claims. Meta-ontology has become a subject in its own right, with deflationary and realist programmes in direct competition. And naturalised metaphysics presses the charge that the armchair tradition ignores the sciences — a charge the section's own treatment of physics takes seriously without conceding.

The recurring shape

One pattern is worth naming, because it recurs in almost every period. Ontological disputes are seldom settled by refutation. They are settled — where they are — by one side showing that the other's primitive is unacceptable, or by a distinction that dissolves the question. Parmenides was answered by distinguishing senses of "is"; the third man by distinguishing self-predication from participation; Quine's attack on modality by distinguishing de re from de dicto; the modal analysis of essence by distinguishing necessity from real definition.

That is a kind of progress, and it is the kind the method page argues is available.