Willard Van Orman Quine was one of the most influential of recent American philosophers. In many ways, he carried on the approach of Bertrand Russell, with its stress on formal logic and ontology.Ontology and Bad Grammar
These summaries and problems deal with Quine's 1948 article, "On What There Is," first published in the Review of Metaphysics. The article is included in Quine's book, From a Logical Point of View (Harper & Row, New York: 1953). These exercise materials are copyrighted (c) 1998 by Harry J. Gensler but may be distributed freely.
Quine sees ontology as trying to answer the question "What is there?" Ontology discusses what kinds of entity exist -- for example, whether there are minds, numbers, or universals (like redness)."To be is to be the value of a variable"
Some are led by poor reasoning into faulty ontologies. For example, McX may reason as follows: "Pegasus [a flying horse of ancient mythology] must in some sense exist -- because if we say 'Pegasus doesn't exist' we have to be talking about something."
McX wrongly takes "Pegasus doesn't exist" to be ascribing a property (of nonexistence) to an object (Pegasus). This misinterprets the sentence "Pegasus doesn't exist." This sentence can be put more clearly as "It is false that there is something that is Pegasus" -- which clearly doesn't assume that Pegasus in some sense exists.
Quine's slogan, "To be is to be the value of a variable," means that we only commit ourselves to an ontology by claims that say things like "There is something (bound variable) that is ..."
For example, "There is something that is a prime number greater than a million" commits us to believing that such numbers are entities. And "There is some property (or characteristic) that red houses and red cars have in common" commits us to believing that properties (or characteristics) are entities.
Quine's slogan doesn't tell us which ontology is true or which we should accept. It only tells us how we commit ourselves to a given ontology.