The historical emergence of supposition theory was the topic of De Rijk’s groundbreaking study Logica modernorum, published in three volumes (De Rijk 1962/ 1967) and including the edition of a wide range of twelfth-and thirteenth-century crucial (anonymous) texts. De Rijk identified two main traditions contributing to the development of supposition theory: the tradition of commentaries on Aristotle’s Sophistical Refutations and, more generally, of theories of fallacies; and the tradition commenting on the fourth-century grammarian Priscian. This account is still thought to be essentially correct, but since the publication of De Rijk’s study, some scholars (e. g., Ebbesen 1981 Have questioned certain aspects of De Rijk’s account. Also, it appears that other elements (such as the theological tradition stemming from Gilbert of Poitiers’ writings; see Kneepkens 1987 And Valente forthcoming) must also be taken into account to explain these developments. Furthermore, it is now believed that a more cautious timeframe for the seminal texts would be the very last decades of the twelfth century and the first decades of the thirteenth century, differing thus from De Rijk’s earlier dating of these texts. Nonetheless, the significance of these two traditions - the grammarian tradition and the tradition on the fallacies - is beyond any doubt, so let us examine how exactly the suppositional framework may have emerged from them.
At this early stage (second half of the twelfth century), suppositio is often related to the syntactic act of putting a term as the grammatical subject of a proposition (see Kneepkens 1987). But it has been argued (Ebbesen 1981) that even at this early stage, the suppositio terminology is used not only to refer to a syntactic act but also to the semantic relation between a term and what it stands for, which was later to become the standard notion of suppositio. In fact, these two apparently different acceptations of the suppositio terminology (present, for example, in the twelfth-century grammarian Peter Helias, whose Summa super Priscianum is a key text for these developments) - the syntactic one and the semantic one - are not really dissimilar if one considers that the prototypical subject of a proposition is a substantive noun and that, according to the grammatical tradition following Priscian, a noun signifies a substance together with a quality. Hence, by placing a noun as the subject of a proposition, one also naturally invokes the substance that the noun signifies. The noun ‘‘man,’’ for example, signifies the individual primary substances that are men insofar as they instantiate the universal nature humanity, and thus it may stand for men in a proposition. Moreover, following Aristotelian hylomorphism, universal natures and qualities are usually viewed as corresponding to forms, which are combined with matter to give rise to individuals. Thus, in the twelfth century, to be a suppositum is regularly used in the sense of being the bearer of a name or, equivalently, of a form/quality: and indeed, the notion of ‘‘bearer of form’’ is (according to Ebbesen 1981:38) crucial in the early development of supposition theory.
Unsurprisingly, in this period supposition is often viewed as a property pertaining exclusively to the subject term, the corresponding property for predicates being copulation; but soon thereafter (e. g., in the first English texts of the thirteenth century - Logica ‘‘Cum sit nostra,’’ Logica ‘‘Ut dicit’’’ and Introductiones Parisienses), supposition is seen as a property of predicates as well.
But even at this early stage, it is also widely acknowledged that terms can be used to stand for things other than
Homo est dignissima
Creaturarum
Sortes est homo
Ergo Sortes est dignissima
Creaturarum
What they signify depending on the specific context of use. Particularly in the formulation of grammatical theories, one must often use a term to talk about the very term itself (for example, to say that ‘‘man’’ is a noun and that ‘‘to run’’ is a verb), and thus not to talk about the thing(s) they usually stand for. Now, in order to indicate this autonymic use of a term, twelfth-century authors belonging to the grammatical tradition (such as in William of Conches, Adelard of Bath and Peter Helias (De Rijk 1962:108109)) often spoke of terms being ‘‘materially imposed’’ (materiale impositum) in such cases. The notion of materiale impositum is the forerunner of the later notion of material supposition (see Rosier-Catach 2003), to appear for the first time in William of Sherwood, which again indicates the crucial role of the grammarian tradition for the development of supposition theory.
As for the fallacies tradition, it is immediately apparent why the fact that the very same term can be used in different acceptations is of crucial importance for the diagnosis of fallacious arguments; Ebbesen (1981:39) argues that in the twelfth century this might have been seen as the main purpose of supposition theory. Generally speaking, fallacies are arguments that appear to be sound in that they seem to display one of the forms usually associated with sound arguments (for example, a valid syllogistic mood), but which are in fact unsound in that they feature true premises leading to (what appears to be) a false conclusion. The challenge is to identify where the problem lies, i. e., what (semantic) phenomenon is behind the false appearance of validity. A standard example of a fallacy is:
(Man is the worthiest of creatures)
(Socrates is a man)
(So Socrates is the worthiest of creatures)
This is an obvious fallacy because the premises are true but the conclusion is false, and yet it does seem to present a valid (syllogistic) form. Intuitively, we immediately perceive that the problem lies in the different uses of the middle term ‘‘man’’ in the first and second premises: in the first one, ‘‘man’’ seems to stand for the nature common to all men, i. e., humanity, while in the second one it seems to stand for a particular man, i. e., an individual instantiating the common nature.
Traditionally, a fallacy such as this one is diagnosed as a fallacy of equivocation, as ‘‘man’’ is used in equivocal ways in the first premise and in the second premise. Now, it is precisely this variation of uses of one and the same term in different propositional contexts that supposition theory seeks to codify. In the case of the example above, supposition theory will allow the theorist to say that the term ‘‘man’’ supposits for different things in the first and second premises (a common nature vs. an individual man), and thus that it has different kinds of supposition. Typically, the occurrence of ‘‘man’’ in the first premise is said to have simple supposition (insofar as the proposition is true), whereas the occurrence of the same term in the second premise is said to have personal supposition (insofar as the proposition is true). Indeed, in the fourteenth century, with Ockham (Summa logicae I chap. 65) and Burley (De puritate Longer Treatise §44), the distinction between personal, simple, and material supposition is still associated to the fallacy of equivocation. Now, for an inference to be valid, the recurring terms must supposit for the same things in all premises, and thus must have the same kind of supposition; in these early developments, one encounters formulations of rules of the form ‘‘no inference is possible from supposition A to supposition B’’ (Ebbesen 1981:39).
World History
