A Mediaeval Perspective on the Meaningfulness of Fictitious Terms: A Study of John Buridan

A MEDIAEVAL PERSPECTIVE ON THE MEANINGFULNESS OF FICTITIOUS TERMS: A STUDY OF JOHN BURIDAN Introduction The following appears to be an uncontroversial theorem of first order predicate logic which can accommodate identity: For all ?, ? = x. The above theorem is sometimes called "the Law ofIdentity" and is at the bottom of anything that might be called "common sense." Why, then, a person might question this law would, at first blush, appear as either some kind of joke or sarcastic manipulation of the expression and intent of the law. However, I will show how the fourteenth-century logician, John Buridan, would not only question this law, but in fact find it to be an overgeneralization until and unless certain qualifications are placed on it. I will argue my case in four stages by first sketching enough of mediaeval supposition theory as to show both what Buridan himself maintained and how that theory of supposition affects interpreting sentences and the terms within them. Secondly, I will go into Buridan's view on fictitious terms. Thirdly, I shall present an apparent paradox generated by a consequence of the Law of Identity, which I maintain will, on Buridan's view, become false. Lastly, I will try to show how to resolve the apparent paradox and, in a manner, reconcile Buridan's view with the Law of Identity. 74NICHOLAS HABIB I. Mediaeval Supposition Theory Mediaeval nominalists are probably best known for their rejection of the view that there are no referents for universal terms such as 'red,' 'horse,' or 'rational' except for individual beings or events. However, this view did not preclude a nominalist such as John Buridan from maintaining that there is a natural, mental language to which a properly formulated conventional language of discourse would correspond . Indeed, it was held that "mental terms" (signs, intentions, or concepts) were prerequisite to the need and employment of conventional terms.1 However, Buridan and his contemporaries, such as Ockham and Albert of Saxony, proceeded with the logical analysis of language in terms of the syntactic/semantic relations of terms in given propositions (sentences).2 The theoretical technology used for such an analysis was supposition theory. A difficult, but provocative, starting place is the following definition of "supposition" given by Buridan: Supposition, as here understood, is the interpretation of a term in a proposition for some thing or things such that, if it or they be indicated by the pronoun 'this' or 'these' or an equivalent, that term is truly affirmed by way of the copula of that proposition.3 In effect, the following characterizes, so far, what supposition was for Buridan: (1)supposition is an interpretative function assigned to a term in a proposition (sentence), (2)a term in a proposition was presupposed to have a significative (referential) function such that a demonstrative pronoun could be used to "pick out" the object to which one is referring, and (3)supposition is a term to term (typically, subject to predicate) and term to pronoun (or pointing behavior) function. 1 Ernest Moody, Truth and Consequence in Mediaeval Logic (Amsterdam: North-Holland, 1953) 18. 2 Moody 19. See also Jon Pinborg, The Logic of John Buridan, Acts of the 3rd European Symposium on Mediaeval Logic and Semantics (Copenhagen: 1976) 77-8. 3 Moody 21. Buridan on the Meaningfulness of Fictitious Terms75 The above three points about supposition form the basis of supposition theory which for Buridan was critical to the establishment of truth conditions for sentences. Buridan maintained that signification alone was inadequate to account for propositional truth because "it fails to mark out adequately what thing or things are being spoken about or referred to by a proposition."^ That is, one must understand how words in a proposition are being used. Buridan distinguished between personal and material supposition. That distinction may be summarized as follows: Personal supposition occurs when terms are used to supposit (stand) for nonlinguistic objects which they signify. An example of a term being used in personal supposition would be (A)Plato is white. In the case of (A), its truth would turn on a mapping of the term 'Plato' onto a demonstrative pronoun which could pick out Plato, the man, and to detect whether or...