criterion of ontological commitment

The criterion of ontological commitment, a concept in philosophy, is primarily associated with the work of philosopher W.V.O. Quine. It addresses the question of what entities a theory commits its holder to, essentially defining what "exists" within the framework of that theory.12

Quine's influential slogan is: "To be is to be a value of a bound variable". This means that a theory is ontologically committed to those entities that must be capable of replacing variables in its logical expressions for the theory's statements to be true. In simpler terms, if a theory requires certain things to exist for its claims to hold, then that theory is committed to the existence of those things. This criterion helps philosophers analyze and compare the "ontologies" or sets of existing entities proposed by different theories, often leading to debates about rich versus sparse ontologies.12