Does the colour green exist, or only green things? Ontology still argues
Socrates was one of a kind; the colour green turns up everywhere. Is green a real thing in its own right, an idea in our heads, or nothing at all? Ontology, the philosophy of being, asks what ultimately exists, and its answers now quietly shape how computers organise information.
The word joins Greek roots for being and study, but the Greeks never used it: philosophers coined it in the 17th century, though speculation about existence goes back to ancient India, China and Greece. Where biology or astronomy stick to one slice of reality, ontology looks at features shared by absolutely everything. Its relation to metaphysics is contested. One traditional view makes it general metaphysics, set apart from special topics such as God, mind and value; others treat it as a preliminary stocktake of what exists, and some use the two words interchangeably.
A central task is sorting reality into basic kinds. Particulars are unrepeatable individuals, like a single philosopher; universals are repeatable, like a colour. Concrete things such as a tree sit in space and time, while abstract ones such as the number 5 do not. Proposed top-level kinds range over substances, events, relations, properties and states of affairs. Aristotle held that things in different categories exist in different ways; John Duns Scotus insisted everything exists in the same way. Plato entertained degrees of being, though most philosophers today say something simply exists or does not.
Fierce disagreements follow. Platonic realists grant universals objective reality, conceptualists place them only in minds, and nominalists deny them outright. Materialists say only matter is fundamental; dualists count mind as an independent principle. Similar fights surround numbers, unobservable scientific entities and moral facts. George Berkeley went furthest, arguing that to exist is to be perceived. The Eleatic principle offers another test: only things with causal power are truly real. Some thinkers doubt these questions have objective answers at all, blaming differences in how languages carve things up.
Methods range from analysing concepts and experience to thought experiments and borrowing results from science. Applied ontology takes the theory into specific fields. Social ontology probes the basic concepts of the social sciences, and computer scientists build ontologies, structured schemes of concepts and relationships, so that systems like a college database can store and link information consistently. Talk of the ontology of genes uses the word in exactly this inventory sense.
Source: Ontology
