On Interpretation, Leśniewski's Ontology, and the Study of Medieval Logic

NOTES AND DISCUSSIONS 217 ON INTERPRETATION, LESNIEWSKI'S ONTOLOGY, AND THE STUDY OF MEDIEVAL LOGIC The most characteristic thing about D. P. Henry's interesting studies of medieval logic is his persistent use of and appeal to the logical system called Legniewski's Ontology . Whether this characteristic of his books and essays is useful or repellent to the reader is a matter of controversy, and the use of this particular interpretative tool has, in fact, been challenged on the ground that if Legniewski's Ontology is taken as an interpreted system in the sense in which medieval logics must be seen to be interpreted, it must be regarded as committed to a two-name doctrine of predication and, hence, is good Oekhamism but a dubious device for the expression of anti-Ockhamist logics.1 Henry has responded that this objection is mistaken.2 There is no reason to believe that Ontology is thus limited. Nevertheless, Ontology is an interpreted system in the strong sense intended in the criticism. Indeed, he says about my characterization of the difference between logic and an uninterpreted calculus, "In fact the view of logic propounded is exactly the one adopted by Legniewski.''3 The aim of this note is to attempt some clarification of this controversy about the use of Le~niewski's Ontology as an analytical and historiographic tool. Henry's understanding of what the medieval logicians were trying to do is totally unexceptionable, but I shall suggest it is far from easy to get, either from him or from Le~niewski's other interpreters, a coherent and consistent understanding of the philosophical point of view of Ontology, upon which one might base a judgement about its historiographic usefulness . The key to the problem is to be found in understanding what it means or can mean to talk about the interpretation of logic; it is here that an attempt at clarifying these issues must begin. There are various ways in which one can speak of the interpretation of logic. The sense of interpretation that concerns this note is one in which from a consideration of the interpretation of a logical system one can ask questions about its ontological commitments . Interpretation here is obviously a matter of semantics; roughly speaking, if we ask questions about how a logical system may be committed to some doctrine about what there is, we shall first look for our answers in a consideration of the devices of the system for referring. We may or may not also consider other putatively related matters concerning descriptive and representational possibilities of the interpreted system; on this seem to hang disputes between philosophers like W. V. Quine and G. Bergmaun, who otherwise agree about the possibility of investigating ontological commitments of interpreted systems. One can easily distinguish various ways of talking about formal systems according to the extent to which questions of ontological commitment arise. (1) One can talk about a formal system strictly syntactically, as though its elements were meaningless marks or counters in a game, and refuse to consider any questions 1 John Trentman, "Le~niewski's Ontology and some Medieval Logicians," Nolre Dame Journal oJ Formal Logic, VII (1966), 361-364. 2 His response first appeared in "Le~niewski's Ontology and some Medieval Logicians," NDJFL, X (1969), 324-326; the substance of his arguments is repeated in his Medieval Logic and Metaphysics (London, 1972).In this note I shall concentrate on Henry's use of Le~niewski and his defenceof that use in this book (hereafter cited as MLM). MLM,p. 54. 218 HISTORY OF PHILOSOPHY about interpretation and ontology. This point of view goes well with the familiar tag of the vintage Carnap: "In logic, there are no morals.'4 (II) One can say about a formal system that it can be interpreted in various ways to yield various sets of ontological commitments. The system itself, according to this view, is neutral with respect to ontological questions. Philosophers may use it as they like, possibly to express opposed ontological commitments. (II1) One can say about a formal system that its structure on interpretation reflects the true (and only the true) ontology. It may indeed be designed with a...