Are scientific theories full of truth-value gaps?
I'm almost done writing a paper that argues that if one accepts the pessimistic induction over the history of science, then one should be a semantic anti-realist about current science -- or should hold unorthodox views in philosophy of language. Here's the argument:
(P1) Certain claims that (a) contain terms with defective reference, or (b) exhibit presupposition failure, are neither true nor false.
(P2) Some fundamental theoretical claims of earlier science exhibit the type of (a) defective reference (e.g. 'phlogiston,' 'absolute velocity,' 'Vulcan') or (b) presupposition failure (e.g. 'Events A and B are simultaneous') described in (P1).
(C1) Therefore, some fundamental theoretical claims of earlier science are neither true nor false.
(P3) Present science probably resembles past science. [That's the step borrowed from the pessimistic induction]
(C2) Therefore, some fundamental theoretical claims of present science are neither true nor false.
The main objections, I think, are:
1. Sentences that contain non-referring terms or exhibit presupposition failure are false, not truth-valueless.
2. Specifically, natural kind terms that fail to pick out a kind/ property (e.g. 'phlogiston') do not generate truth-value gaps (even supposing proper names that fail to pick out an individual do generate truth-value gaps).
I offer replies to these objections, but none of them are absolutely decisive. So, my more tentative conclusion is that a proponent of the pessimistic induction either has to accept my original conclusion OR accept a currently unpopular position in philosophy of language -- e.g. one could justify objection 2 by appealing to a descriptivist account of natural kind terms, but that would fall afoul of the widely endorsed Kripke-Putnam arguments against such descriptivism.
I'll be giving this material as a talk at the University of Utah in a couple of weeks, so any feedback before then would be especially appreciated.