Ontology

Ontology asks what exists and whether existence divides into kinds. The beginner tier fixes the vocabulary of existence, objects, properties, identity, and ontological commitment without assuming any prior technical training. The intermediate tier works through Quine's criterion and its truthmaker rival, the abstract and concrete divide, natural kinds, mathematics, non-existent objects, composition, and the Carnap dispute that set the modern agenda. The advanced tier is metaontology and the formal end of the field: easy ontology, quantifier variance, absolute generality, plural and higher-order quantification, grounding, and joint-carving.

Beginner

No prior exposure assumed. Every term is defined where it first appears.

What 'Exists' Means
The difference between existing, being real, and merely being talked about
8 min
Candidate Existents
Ordinary things, happenings, qualities, and numbers, and why the last two are contested
10 min
Needs firstWhat 'Exists' Means
Universals and Instances
One thing said of many, and the first question anyone asks about properties
9 min
Needs firstCandidate Existents
Identity and Individuation
Counting things requires knowing when you have one or two, and that turns out to depend on what kind they are
10 min
Needs firstUniversals and Instances
Is Existence a Property?
Kant's complaint that adding 'and it exists' says nothing about a thing, and Frege's way of making that precise
10 min
Needs firstIdentity and Individuation
Ontological Commitment, Informally
What a theory says there is, and how rewriting a sentence can change the answer
9 min
Needs firstIs Existence a Property?

Intermediate

Undergraduate level. Formal machinery, standard results, and the objections that stuck.

Quine's Criterion and 'On What There Is'Planned
To be is to be the value of a bound variable, and what that test does and does not settle
16 min
The Truthmaker Rival to Quine's CriterionPlanned
Reading commitment off what has to exist for a sentence to be true, rather than off what it quantifies over
17 min
Categories of BeingPlanned
Whether being divides into kinds, or applies in one single sense to everything there is
14 min
Drawing the Abstract/Concrete LinePlanned
Four ways of drawing the line, by causal power, location, mind dependence, and abstraction
15 min
Natural KindsPlanned
Whether the divisions we sort things into are found or made, and what a kind would have to be to be found
17 min
Mathematical Platonism and NominalismPlanned
The indispensability argument for numbers, and the nominalist strategies for doing without them
18 min
Fictional and Non-Existent ObjectsPlanned
Meinong on objects that bear properties without existing, and Russell's objections to them
17 min
Mereological CompositionPlanned
When some things compose a further thing, and the nihilist and universalist answers
18 min
Ontological Categories in Aristotle and HusserlPlanned
Substance and accident in the Categories, and Husserl's dependence relations between regions
19 min
Carnap's Internal and External QuestionsPlanned
Questions asked inside a framework against questions asked about it, and Quine's reply
24 min

Advanced

Graduate level. Metatheory, technical variants, and disputes that are still open.

Metaontology and the Substantivity DisputePlanned
Whether ontological disputes are genuine disagreements or artifacts of how the parties speak
22 min
Easy OntologyPlanned
Deriving numbers and properties from trivial inferences, and the claim that the hard questions were never hard
22 min
Neo-Fregean AbstractionPlanned
Deriving arithmetic from Hume's principle, and the Caesar and bad company objections
26 min
Ontological Pluralism and Quantifier VariancePlanned
Whether there are several ways of being, and whether rival ontologists mean one thing by 'there is'
24 min
Absolute GeneralityPlanned
Whether anyone can quantify over absolutely everything, and what indefinite extensibility would cost if not
26 min
Ideology and OntologyPlanned
Counting primitive notions as well as entities, and why the two economies pull against each other
20 min
Plural Quantification and Ontological InnocencePlanned
Talking about some things without talking about a further thing they form, and what nominalism can buy with it
24 min
Higher-Order MetaphysicsPlanned
Asking the questions in a typed higher-order language instead of a first-order one, and watching several of them change shape
28 min
Grounding-Based OntologyPlanned
Ranking what there is by what holds in virtue of what, rather than listing it all flat
26 min
Ontological Realism and Joint-CarvingPlanned
Sider's claim that quantification itself carves at the joints, and what makes a description natural
28 min
Boundaries, Holes, and AbsencesPlanned
The ontology of things that seem to be defined by what is not there, and what they do to a clean mereology
22 min
Formal Ontology and Applied OntologiesPlanned
Upper ontologies built for shared scientific data, and the continuant and occurrent split they turn on
22 min