Free of Detachment: Logic, Rationality, and Gluts
Nousˆ 00:00 (2013) 1–14 Free of Detachment: Logic, Rationality, and Gluts JC BEALL University of Connecticut 1. Introduction Glut theorists maintain that some sentences are true and false—true with true negations. The best examples of such gluts are antinomies (e.g., the liar paradox). My aim here is not to argue for glut theory; that has been done elsewhere [3, 5, 6, 21,22,35,36,46]. My aim is to address a longstanding and very common objection to glut theories. The objection, roughly, is: (1) Glut theory involves the invalidity of material modus ponens (or, on its con- temporary tag, material detachment): {A, A ⊃ B} ∴ B is invalid. (2) Material detachment is central to our theoretical work. (3) Without some way to understand how we pursue common theoretical work without the validity of detachment, glut theory remains not only a highly radical idea; it is simply implausible—full stop. The dominant reply by glut theorists over the last four decades [4–6, 17, 31, 36, 38, 51] is to concede (1), for reasons briefly reviewed in §5 below, but, towards answering (2) and (3), proceed on a quest for (non-material) detachable conditionals, generally following the lead of Anderson and Belnap’s work and that of others in the ‘relevance’ tradition [1, 2, 17, 23, 31, 32, 38, 39, 42, 47, 50].1 But as Dunn, Meyer and Routley noted early on [33], Curry’s paradox riddles the quest for detachable conditionals with severe problems; and overcoming the problems makes for very complicated, philosophically awkward semantics [9], and indeed often engenders the need to find yet other detachable conditionals to serve other pressing needs (e.g., restricted quantification) [10,12,19].
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