Quine, Willard Van Orman - Confessions of a Confirmed Extensionalist

01/12/2007

Future Pasts, Floyd & Shieh eds., Oxford Univ Press

Author introduces himself as an extensionalist. He defines what coextensive means for various parts of speech:

-2 Closed Sentences: coextensive if both true or both false
-2 Predicates/General Terms/Open Sentences: coextensive if true of just the same objects or sequences of objects
-2 Singular Terms: coextensive if they designate the same object

An expression is extensional if replacing one of its parts with a coextensive part preserves truth.

Two main problems for extensionalism:
1) intentional claims about beliefs with more than one mode of presentation.
2) Using a term for fictitious objects like 'pegasus', then using 'flies if existent' and 'flies and exists', using existence as a property. The two predicates are coextensive, but one is true and the other false. Author fixes this problem by translating 'flies if existent' to 'exists, then flies', which is false too.

Author talks of the problem of Principia Mathematica was to use "Propositional Functions", which led back to properties and intentions rather than individuated extensional items. The other issue was 'material implication', which got seriously confused in Principia Mathematica by using 'p implies q' to suggest 'p entails q'. This leads to confusion because it can seem as though 'p entails q' is a necessary truth between p and q, which author refuses.

The first problem of extensionalism is intentions-- 'Tully' and 'Cicero'. If we mention, not use, the sentence 'Cicero denounced Catiline' in the sentence 'Tom believes "...". Then since the sentence 'Cicero...' is mentioned, you cannot substitute into it.

This is 'semantic ascent', which can be very useful. "The quoted sentence is the ascriber's expression of what he would be prompted to assert if he were in the state of mind in which he takes the subject to be." This has no internal component, just external 'assent', etc.

Later, in the meeting, a big complaint of semantic assent was the lack of translation (into other languages, for instance)-- you need meanings for this.