Francois Lepage

The aim of this paper is to present a strongly complete first order functional predicate calculus generalized to models containing not only ordinary classical total functions but also arbitrary partial functions. The completeness proof follows Henkin’s approach, but instead of using maximally consistent sets, we define saturated deductively closed consistent sets . This provides not only a completeness theorem but a representation theorem: any SDCCS defines a canonical model which determine a unique partial value for every predicate symbol and any function symbol. Any SDCCS can thus be interpreted as an epistemic state

This paper has four parts. In the first part, I present Leniewski's protothetics and the complete system provided for that logic by Henkin. The second part presents a generalized notion of partial functions in propositional type theory. In the third part, these partial functions are used to define partial interpretations for protothetics. Finally, I present in the fourth part a complete system for partial protothetics. Completeness is proved by Henkin's method [4] using saturated sets instead of maximally saturated sets. This technique provides a canonical representation of a partial semantic space and it is suggested that this space can be interpreted as an epistemic state of a non-omniscient agent.

This paper presents a generalization of a proposal of van Benthem’s who has shown how to provide a canonical name for any object in propositional type theory. Van Benthem’s idea is to characterize any function in the hierarchy by the Boolean values the function takes for any sequence of arguments. The recursive definition of canonical names uses only the abstraction, functional application, the identity operator and the fact that we have a name for the true and the false. We show that this result can be extended to the finite theory of types by the introduction of an algebra on individuals

Parmi l'ensemble de toutes les propositions à propos desquelles un agent rationnel entretient des croyances et des désirs, certaines correspondent à des actes que l'agent juge faisables. Le but de mon intervention est de caractériser ce sous-ensemble de propositions en termes de leur probabilité et de leur désirabilité.Among the set of all propositions on which a rational agent entertains beliefs and desires, some express acts considered as possible options for the agent. The aim of this paper is to characterize this subset of propositions in terms of their probability and their desirability