# Metaphysics Ontology

> Master metaphysics and ontology - the study of being, existence, and fundamental reality. Use for: existence, being, substance, identity, causation, modality, time, universals. Triggers: 'ontological', 'metaphysical', 'what exists', 'substance', 'essence', 'existence', 'being', 'identity', 'persistence', 'causation', 'modality', 'possible worlds', 'universals', 'particulars', 'properties', 'abstract objects', 'time', 'change', 'composition'.

- Skill: `majiayu000/metaphysics-ontology` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/metaphysics-ontology`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/metaphysics-ontology/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/metaphysics-ontology

---


# Metaphysics & Ontology Skill

Master the fundamental questions of metaphysics: What exists? What is being? What is the ultimate nature of reality?

## Core Questions

### Fundamental Issues

| Question | Field | Examples |
|----------|-------|----------|
| What exists? | Ontology | Numbers? Properties? Possible worlds? |
| What is being? | Fundamental ontology | Being vs. beings |
| What are things made of? | Substance metaphysics | Matter, form, properties |
| What makes something the same over time? | Persistence | Personal identity, ship of Theseus |
| What is causation? | Causal metaphysics | Regularity, counterfactual, powers |
| What is possible/necessary? | Modality | Possible worlds, essence |

---

## Ontology: What Exists?

### Ontological Categories

```
ONTOLOGICAL LANDSCAPE
═════════════════════

CONCRETE PARTICULARS
├── Physical objects (tables, planets)
├── Mental events (thoughts, pains)
└── Persons

ABSTRACT OBJECTS (?)
├── Numbers, sets
├── Propositions
├── Properties/universals
└── Possible worlds

EVENTS AND PROCESSES
├── The Battle of Waterloo
├── The melting of ice
└── My walking to work

FACTS AND STATES OF AFFAIRS
├── That snow is white
├── The redness of the apple
└── The table's being square
```

### Platonism vs. Nominalism

**Platonism**: Abstract objects exist
- Numbers exist independently of minds
- Properties are real universals
- Mathematical truth is discovery, not invention

**Nominalism**: Only particulars exist
- No abstract objects
- "Redness" is just a word for similar things
- Mathematical objects are useful fictions

---

## Substance and Properties

### Substance Theories

**Aristotelian Substance**:
- Primary substances: individual things (this horse)
- Secondary substances: kinds (horse, animal)
- Substances persist through change; accidents don't

**Bundle Theory**:
- No underlying substance
- Objects = bundles of properties
- Problem: What ties the bundle together?

**Substratum Theory**:
- Bare particulars underlie properties
- Problem: What is bare substratum? Unknowable?

### Properties

**Universals vs. Tropes**:
| Universals | Tropes |
|------------|--------|
| One property, many instances | Each instance a particular |
| "Redness" is one thing | This red ≠ that red |
| Shared by objects | Resembling particulars |
| Explains resemblance | Avoids mysterious sharing |

---

## Identity and Persistence

### Personal Identity

**Theories**:
```
PERSONAL IDENTITY THEORIES
══════════════════════════

PSYCHOLOGICAL CONTINUITY
├── Memory, personality, beliefs
├── Locke: consciousness makes identity
├── Parfit: What matters isn't identity
└── Problems: Fission, amnesia

BIOLOGICAL CONTINUITY
├── Same organism = same person
├── Animalism (Olson)
└── Problems: Transplant cases

SOUL/SUBSTANCE VIEW
├── Immaterial soul persists
├── Problems: Interaction, detection
└── Forensic vs. metaphysical identity
```

### Ship of Theseus

```
SHIP OF THESEUS
═══════════════

Original ship's planks gradually replaced.
Is it still the same ship?

VARIANT: Old planks reassembled into second ship.
Which is the original?

POSITIONS:
├── Neither (no real identity)
├── Repaired ship (spatial continuity)
├── Reassembled ship (material continuity)
└── Both partially (graded identity)
```

---

## Causation

### Theories

**Regularity Theory** (Hume):
- Causation = constant conjunction
- No necessary connection
- "Cement of the universe" is just habit

**Counterfactual Theory** (Lewis):
- C causes E iff: If C hadn't occurred, E wouldn't have
- Analyzed via possible worlds

**Powers/Dispositions**:
- Causes have intrinsic causal powers
- Salt's solubility is real property
- Not reducible to regularities

**Process/Mechanism**:
- Causation = physical process
- Transfer of energy, momentum
- Tracing causal history

---

## Modality

### Possible Worlds

**Modal Claims**:
- Necessarily P: P is true in all possible worlds
- Possibly P: P is true in some possible world
- Contingently P: P is true but could be false

**What Are Possible Worlds?**:
```
POSSIBLE WORLDS REALISM
═══════════════════════

MODAL REALISM (Lewis)
├── Possible worlds are concrete realities
├── As real as actual world
├── "Actual" is indexical (like "here")
└── Controversial but powerful

ERSATZISM
├── Possible worlds are abstract objects
├── Sets of propositions, or
├── Maximal states of affairs
└── More conservative

FICTIONALISM
├── Possible worlds are useful fictions
├── No commitment to existence
└── Instrumentalist reading
```

### Essence and Necessity

**Essential Properties**: Properties a thing must have to be that thing
**Accidental Properties**: Properties a thing happens to have

**Kripkean Essentialism**:
- Origin is essential (you couldn't have different parents)
- Natural kinds have essences (water = H₂O necessarily)
- Names are rigid designators

---

## Time

### Theories of Time

**A-Theory (Tensed)**:
- Past, present, future are real
- Present is metaphysically special
- Time flows

**B-Theory (Tenseless)**:
- Only earlier-than, simultaneous, later-than relations
- No privileged present
- "Block universe" — all times equally real

### Persistence Through Time

**Endurantism**: Objects are wholly present at each moment
**Perdurantism**: Objects have temporal parts (stages)

```
PERSISTENCE VIEWS
═════════════════

ENDURANTISM               PERDURANTISM
├── Object wholly         ├── Object has temporal parts
│   present at each time  │   (like spatial parts)
├── Properties change     ├── Different stages have
│   (intrinsic change)    │   different properties
└── Intuitive but         └── Handles change better but
    faces puzzles             counterintuitive
```

---

## Composition

### The Special Composition Question

When do parts compose a whole?

**Universalism**: Any objects compose something
**Nihilism**: No composite objects exist
**Restricted**: Some conditions required (contact, life, etc.)

### Mereology

- Part-whole relations
- Proper vs. improper parts
- Transitivity of parthood
- Supplementation principles

---

## Key Vocabulary

| Term | Meaning |
|------|---------|
| Ontology | Study of what exists |
| Metaphysics | Study of fundamental nature of reality |
| Substance | What exists in itself |
| Property | What is attributed to substance |
| Universal | One thing shared by many |
| Particular | Individual, unrepeatable |
| Trope | Particular instance of property |
| Modal | Concerning possibility/necessity |
| A priori | Independent of experience |
| A posteriori | Dependent on experience |
| Essence | What makes thing what it is |
| Accident | What thing contingently has |
| Supervenience | No A-difference without B-difference |
| Haecceity | Thisness; individual essence |

---

## Integration with Repository

### Related Themes
- `thoughts/existence/`: Being, reality, metaphysics

### Thought Experiments
- Ship of Theseus
- Teletransporter
- Twin Earth (for natural kinds)