Explainer · Plain-language

What is ontology?

Ontology is the theory of being: the branch of philosophy concerned with what exists and the nature of reality. In research it sets your assumptions about the world you are studying.

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Ontology in research

In methodology, ontology answers the question: what is the nature of the reality I am investigating? A realist (or objectivist) ontology holds that a single reality exists independently of the people who study it, waiting to be measured. A relativist (or constructionist) ontology holds that reality is multiple and shaped by human perception, language and social context. This is not idle metaphysics: if you believe there is one measurable reality, you design to capture it; if you believe meaning is constructed, you design to interpret it.

Ontology before epistemology

Ontology and epistemology work as a pair, and ontology is usually taken first. Once you have decided what kind of reality exists (ontology), you can ask how that reality can be known (epistemology). A realist ontology naturally invites an objective, measurement-led epistemology; a relativist ontology invites an interpretive one. The combined ontological and epistemological assumptions form the foundation of a research paradigm, which then guides methodology and choice of method.

Why it matters

Stating your ontological position keeps a study internally coherent and defensible. Reviewers expect the assumed nature of reality, the way you claim to know it, and your chosen methods to line up. An explicit ontology also clarifies what your findings can claim: a relativist study reports situated meanings rather than universal laws, whereas a realist study aims at generalisable, replicable measurement. Naming the position prevents a mismatch that examiners quickly spot.

Key facts

At a glance

Definition: the philosophical theory of being — what exists and what is real
Field: core branch of philosophy, alongside epistemology
Core question: what is the nature of reality being studied?
Main positions: realist/objectivist vs relativist/constructionist
Paired with: epistemology (how we know) within a paradigm
In research: fixes the assumptions your design and claims rest on

Common misconceptions

What people often get wrong

Often heard: Ontology and epistemology are interchangeable terms.

Actually: Ontology asks what exists and what reality is like; epistemology asks how we can know it. They are distinct but linked, and ontology is usually decided first.

Often heard: Ontology only matters in philosophy, not in practical research design.

Actually: Your ontological assumption — one objective reality or multiple constructed ones — directly determines whether you measure or interpret, and what your findings can legitimately claim.

Often heard: A serious researcher must adopt a realist ontology to be scientific.

Actually: Realist and relativist ontologies are both defensible. Qualitative traditions often adopt relativist assumptions and remain rigorous; the requirement is coherence, not one fixed stance.

Going deeper