Abstract

This study of the medieval semantic notion of suppositio naturalis provides an examination of late-medieval accounts of the truth conditions of statements of essence or nature, i.e. the sentences appropriate to demonstrative science. The supposition theories of Walter Burley, William of Ockham, John Buridan, and Vincent Ferrer are compared in view of their different metaphysical and epistemological perspectives. ;A categorical term in a proposition has supposition when it stands for some thing or things. For medieval scientists/philosophers/logicians, propositions of demonstrative science are categorical in form, are necessarily and eternally true, yet are meant to speak of the created, contingent world. The question which the four above-mentioned authors must address is: how do substantival terms in essential predications stand for things so that the propositions of demonstrative science are necessarily and eternally true? ;The first of the six chapters introduces this problem of linking human words, the created world, and scientific knowledge. Chapter II clarifies definitions and distinctions regarding the properties of categorical terms. Analysis of key medieval texts and critical assessment of Twentieth century interpretations of medieval supposition theory serve to clarify the terminology used in the subsequent chapters. ;Chapter III addresses the ontological, epistemological, and logico-semantical disagreements between Ockham and Burley . Both authors fail to develop a satisfactory semantics for propositions of demonstrative science. ;Chapter IV further explores nominalism through the work of Buridan; while Ferrer's work, examined in Chapter V, provides a realist counterpart. Both authors realize the difficulties of linking the universal terms of necessary propositions to a world made up of contingent individuals. Buridan develops suppositio naturalis as omnitemporal supposition to explain the truth of scientific statements through time. Ferrer develops a theory of suppositio naturalis as atemporal supposition whereby terms stand for the common nature of individuals. ;Chapter VI discusses the philosophical tolerance of suppositio naturalis and links these medieval views to current studies on the logic of essential predication