Our acceptance of an ontology is, I think, similar in principle to our acceptance of a scientific theory, say a system of physics;we adopt, at least insofar as we are reasonable, the simplest conceptual scheme into which the disordered fragments of raw experience can be fitted and arranged.
Willard Van Orman QuineJust as the introduction of the irrational numbers ... is a convenient myth [which] simplifies the laws of arithmetic ... so physical objects are postulated entities which round out and simplify our account of the flux of existence... The conceptional scheme of physical objects is [likewise] a convenient myth, simpler than the literal truth and yet containing that literal truth as a scattered part.
Willard Van Orman QuineAn indirect quotation we can usually expect to rate only as better or worse, more or less faithful, and we cannot even hope for astrict standard of more and less; what is involved is evaluation, relative to special purposes, of an essentially dramatic act.
Willard Van Orman QuineThe variables of quantification, 'something,' 'nothing,' 'everything,' range over our whole ontology, whatever it may be; and we are convicted of a particular ontological presupposition if, and only if, the alleged presuppositum has to be reckoned among the entities over which our variables range in order to render one of our affirmations true.
Willard Van Orman QuineThe lore of our fathers is a fabric of sentences. In our hands it develops and changes, through more or less arbitrary and deliberate revisions and additions of our own, more or less directly occasioned by the continuing stimulation of our sense organs. It is a pale gray lore, black with fact and white with convention. But I have found no substantial reasons for concluding that there are any quite black threads in it, or any white ones.
Willard Van Orman Quine