Reply to Burgess and to Read (Q1086226)

This paper is part of an ongoing, vigorous debate over the validity of extensional disjunctive syllogism (EDS), i.e., A or B, not A/\(\therefore B\). Here Mortensen successfully defends his position put forth in Notre Dame J. Formal Logic 24, 35-40 (1983; Zbl 0476.03005)] against a charge of circularity leveled both by \textit{J. P. Burgess} [Notre Dame J. Formal Logic 24, 41-53 (1983; Zbl 0476.03006)] and by \textit{S. Read} [ibid. 24, 473-481 (1983; Zbl 0569.03005)]. Burgess and Read claimed that Mortensen had appealed to the validity of EDS in arguing for his position (in particular, 4 below) that 1) EDS is not valid, though 2) EDS is reliable when ''things are normal''; 3) intuitive examples of EDS carry the extra assumption of normalcy; and 4) consistency and primeness are jointly sufficient for a theory to be normal. Mortensen points out that he does not appeal to the validity of EDS, but only to its being reliable in a particular theory. He then goes on to address sundry other points raised by Burgess and Read. The general debate over EDS is also engaged by \textit{A. R. Anderson} and \textit{N. D. Belnap} [Entailment (1975; Zbl 0323.02030)], \textit{N. D. Belnap} and \textit{J. M. Dunn} [Contemporary Philosophy: A new survey (Nijhoff, The Hague) (1981)], \textit{R. K. Meyer} [Why I am not a relevantist (Research Papers in Logic, Logic Group, RSSS, Australian National University, Canberra) (1979)], \textit{J. P. Burgess} [Notre Dame J. Formal Logic 25, 217-223 (1984; Zbl 0569.03006)], \textit{J. P. Burgess} [ibid. 22, 97-104 (1981; Zbl 0438.03008)], \textit{R. Routley} [Relevantism and the problem as to when material detachment and the disjunctive syllogism can be correctly used (Research Papers in Logic, Logic Group, RSSS, Australian National University, Canberra) (1983)] and \textit{R. Routley} et al. [Relevant logics and their rivals. I (1982; Zbl 0579.03011)].