Saturday, March 17, 2007

Extensional science

A theme in Quine's writing is that proper languages for the austere purposes of science should be extensional. At one point, if memory serves, he says that if propositional attitude predicates must be intensional, so much the worse for them. They aren't needed in a proper science anyway. Similarly for dispositions. They are good shorthand, but they are modal notions, which are intensional, and so disposable in a proper extensional language of science. Where did this idea originate? I don't remember any arguments in Quine to the effect that scientific predicates are extensional. Is this an idea that can be traced back to the Vienna Circle or someone before then? Davidson picks it up and uses it to argue for some analysis of causation [edit: in "Causal Relations."]. Someone (name escapes me and I can't find the articl [edit: Crane and Mellor's "There is No Question of Physicalism."]) responds to Davidson by arguing that causation is actually an intensional notion [edit: and other intensional contexts appear in physics, e.g. probability]. So, why would one think that scientific notions are essentially extensional anyway? If dispositional properties and counterfactuals or other modal notions are involved in scientific theories, then one wouldn't think that scientific theories are extensional. No idea really.


GC said...


I wish I knew the answer to this too. I wonder if it has anything to do with mathematical predicates being extensional, after all Quine did start out by working on Russell's Principia Mathematica.

GF-A said...

From what I can tell (and I've spent some time rooting around in the Quine archive at Harvard), it is simply one of Quine's absolutely core commitments that any non-extensional characterization/ explication of a term is "unclear." He actually claims, in his "Confessions of a Confirmed Extensionalist" (in the 2001? volume "Future Pasts") that he was an extensionalist by the time he was a freshman at Oberlin. One thing to say is that the idea was in vogue with his philosophical hero Carnap in the late 20s early 30s -- think Logical Syntax of Language, which Quine read as it came off of Ina Carnap's typewriter -- but it falls out of favor with Carnap in later years.

Shawn said...

It seems like whether science (in the appropriate sense; theories? logic?) is not something that can be stipulated. If it turns out that some parts of science use intensional notions, then one can not at the same time demand extensionality and that science be the measure of all things. They aren't compatible.