Ontological Realism
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[Part of: Poetica Philosophica.]
Willard Quinon Would opine on Truth wrought by convention. "Rudolf, buddy, Something's funny 'bout your Method of intension." Meanwhile Carnap Waving foolscap Postulated liberally. "Dearest Van-o, New things I'll grow with my Framework relativity."
Once upon a time, empiricists ruled the land. Their motto: all knowledge rests on observation. But there was a problem. We know that 2+2=4, we know lots of mathematics, but that knowledge is "a priori," not based on observation. Empiricists replied: these are definitional truths. They are true by convention, and outside the scope of their motto. Willard Van Orman Quine (1908-2000) shattered this dream, in "Two Dogmas of Empiricism" (1951) and elsewhere; nothing, he argued, is true by convention. Rudolf Carnap (1891-1970), his friend, adversary, and pen pal, identified the meaning of a sentence with the set of possible situations (intensions) in which it is true; Quine thought this nonsense. Carnap also embraced truth-by-definition, and moderated (or radicalized) it by putting the definitions inside frameworks; 2+2=4 is true-by-definition relative to one framework, and false relative to another. One should adopt the framework that best suits one's needs; none is objectively correct.