Ontological commitment

A person may believe in the existence of God, or numbers or ghosts. Such beliefs may be asserted, perhaps in a theory. Assertions of the existence of specific entities or kinds of entities are the intuitive source of the notion of ontological commitment, for it is natural to think of a person who makes such an assertion as being ‘committed’ to an ‘ontology’ that includes such entities. So ontological commitment appears to be a relation that holds between persons or existence assertions (including theories), on the one hand, and specific entities or kinds of entities (or ontologies), on the other.

Ontological commitment is thus a very rich notion – one in which logical, metaphysical, linguistic and epistemic elements are intermingled. The main philosophical problem concerning commitment is whether there is a precise criterion for detecting commitments in accordance with intuition. It once seemed extremely important to find a criterion, for it promised to serve as a vital tool in the comparative assessment of theories. Many different criteria have been proposed and a variety of problems have beset these efforts. W.V. Quine has been the central figure in the discussion and we will consider two of his formulations below.

Many important philosophical topics are closely connected with ontological commitment. These include: the nature of theories and their interpretation; interpretations of quantification; the nature of kinds; the question of the existence of merely possible entities; extensionality and intensionality; the general question of the nature of modality; and the significance of Occam’s razor.