I argue that the medieval form of dialectical disputation known as obligationes can be viewed as a logical game of consistency maintenance. The game has two participants, Opponent and Respondent. Opponent puts forward a proposition P; Respondent must concede, deny or doubt, on the basis of inferential relations between P and previously accepted or denied propositions, or, in case there is none, on the basis of the common set of beliefs. Respondent loses the game if he concedes a contradictory set (...) of propositions. Opponent loses the game if Respondent is able to maintain consistency during the stipulated period of time. The obligational rules are here formalised by means of familiar notational devices, and the application of some game-theoretical concepts, such as (winning) strategy, moves, motivation, allows for an analysis of some crucial properties of the game. In particular, the primacy of inferential (syntactic) relations over semantic aspects and the dynamic character of obligations are outlined. (shrink)

This paper defends the thesis that the mediaeval genre of logical treatises De obligatiombus contained a theoretical account of counterfacutal reasoning, perhaps the first such account in the history of philosophy. This interpretation helps to explain some of the theoretical disputes in the obligationes literature in the first half of the fourteenth century. Section 1 is introductory. Section 2 presents Walter Burley's theory, while section 3 argues for the counterfactual interpretation of obligationes and section 4 discusses difficulties with Burley's theory. (...) Section 5 presents the textual basis for Richard Kilvington's theory, and section 6 outlines that theory. Section 7 discusses Roger Swyneshed's theory. Section 8 contains a summary and conclusion. (shrink)

J'examine plusieurs sources selon lesquelles Swyneshed (malgré les prétentions d'Angel D'Ors dans ses articles récents) donne une nova responsio en partie sous forme de la règle « On peut nier une proposition conjonctive après avoir concédé ses deux parties. » Je montre que cette nova responsio est liée à un rejet de la règle « Chaque proposition qui suit de l'ensemble de propositions déjà concédées doit être concédée », et j'attribue ce rejet à une théorie selon laquelle une inférence se (...) base sur le rapport logique entre seulement deux propositions. I examine a number of sources according to which Swyneshed (despite the claims made by Angel D'Ors in his recent articles) does give a nova responsio partly in the form of the rule « One can deny a conjunction whose conjuncts have already been granted. » I show that this nova responsio is linked to a rejection of the rule « Every proposition following from a set of propositions which have already been granted must be granted », and I attribute this rejection to a theory whereby an inference is based on the logical relations between just two propositions. (shrink)

This book presents a thorough reconstruction of the late-scholastic logical treatises De Obligationibus by the methods of modern logic and set theory. It defends the view that the treatises are intended to put forward a theory of disputation.