ONT Re: Quine -- Two Dogmas Of Empiricism
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TDOE. Note 14
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| 3. Interchangeability (cont.)
|
| Interchangeability 'salva veritate' is meaningless until relativized to
| a language whose extent is specified in relevant respects. Suppose now
| we consider a language containing just the following materials. There
| is an indefinitely large stock of one-place predicates, (for example,
| "F" where "Fx" means that x is a man) and many-place predicates (for
| example, "G" where "Gxy" means that x loves y), mostly having to
| do with extralogical subject matter. The rest of the language
| is logical. The atomic sentences consist each of a predicate
| followed by one or more variables "x", "y", etc.; and the
| complex sentences are built up of the atomic ones by truth
| functions ("not", "and", "or", etc.) and quantification.
| In effect such a language enjoys the benefits also of
| descriptions and indeed singular terms generally,
| these being contextually definable in known ways.
| Even abstract singular terms naming classes,
| classes of classes, etc., are contextually
| definable in case the assumed stock of
| predicates includes the two-place
| predicate of class membership.
| Such a language can be adequate
| to classical mathematics and
| indeed to scientific discourse
| generally, except in so far as
| the latter involves debatable
| devices such as contrary-to-fact
| conditionals or modal adverbs like
| "necessarily". Now a language of this
| type is extensional, in this sense: any
| two predicates which agree extensionally
| (that is, are true of the same objects)
| are interchangeable 'salva veritate'.
|
| Quine, "Two Dogmas", p. 30.
|
| W.V. Quine,
|"Two Dogmas of Empiricism", 'Philosophical Review', January 1951.
| Reprinted as pages 20-46 in 'From a Logical Point of View',
| 2nd edition, Harvard University Press, Cambridge, MA, 1980.
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