Franciscan Studies

LOGICAL STRUCTURES OF OCKHAM'S THEORY OF SUPPOSITION There are two pervasive themes in this article. In the first place this article is a defense of Ockham against a baseless charge of error, which, if left unanswered, might tend to diminish Ockham's reputation as a technically competent logician. Study of the sources of the charge reveal that two recent commentaries each attribute ingenious and interesting logical structures to Ockham's thought on supposition. Comparison of these two structures with each other and with Ockham's writings yields three results: first, that the two structures , though separately consistent, are inconsistent with each other; second, that neither of them square with Ockham's own statements and, third, that Ockham's thought does have a logical structure which, in several respects, is even more ingenious. Thus, the second theme of this article involves an attempt to articulate the logical structure of Ockham's theory of supposition and to compare this structure with two others that have been proposed. The two themes are interrelated as follow. Mistaking the logical structure of Ockham's system of definitions led to false characterizations of two of Ockham's three kinds of supposition. The false characterizations imply conflicts with Ockham's classification of terms according to supposition. These conflicts were assumed to be internal inconsistencies in Ockham's writings and it was on the basis of these supposed "inconsistencies" that the charge was made.1 The details of what we take to be Ockham's structure are developed in Section ? and 2. Section 3 is devoted to elaborating evidence 1 In this work we have tried to be guided by Boehner's wise advice [Boehner, 1949, 137]: "...there is a greater danger of being led by preconceived ideas or the consistency of an imaginary system and in consequence arriving at a subjective interpretation. We still believe that history should first ascertain facts, and it should attempt to reconstruct a 'system,' if there is any, only after a thorough acquaintance with the sources." Moreover, because this paper concerns an aspect of Ockham's work which was not dealt with by Boehner (see footnote 4 below), there is an important sense in which the present work is a continuation of Boehner's work. Franciscan Studies 162JOHN CORCORAN and JOHN SWINIARSKI to be used in Ockham's defense. Section 4 is at once an exposition of one of the other two structures and, at the same time, a defense of Ockham against the charge made from that point of view. Section 5 does the same as Section 4 but treating of the other structure. Section 6 is a summary of conclusions. An "Introduction" sets the scene. Introduction A cursory reading of the relevant passages in Ockham's Summa Logicae, I, 70, is sufficient to confirm that Ockham holds to three connections: determinate supposition involves a disjunction of propositions , distributive supposition involves a conjunction of propositions, and merely confused supposition involves a proposition having a disjunctive predicate. Swiniarski [1970, 200] explicitly points out these connections. Loux [1974, 26-28] provides an exposition in which he infers that these connections must be mutual entailments. Priest and Read [1977, no] endorse a part of the Loux exposition and, on its basis, they construct a symbolic formalization of Ockham's theory of personal supposition. Priest and Read [109, in] notice that the Loux exposition is inconsistent with Ockham's explicitly and repeatedly expressed view that the predicate of the particular negative proposition has distributive supposition. They go into some detail to show that the Loux exposition implies both ( 1) that the predicate does not have distributive supposition and (2) that it does have merely confused supposition . Priest and Read infer from the inconsistency that Ockham was mistaken about the predicate of the particular negative and they criticize Loux for not having noticed Ockham's "mistake." In this article we show that the inconsistency does not exist in Ockham's writings, but that the trouble is with the Loux exposition . We show that the Loux exposition overlooks important aspects of Ockham's theory. In particular, we show that Ockham held to mutual entailment only in the case of determinate supposition and that, in place of...