Conditionals and belief change

The Ramsey test specifies the meaning of conditionals in terms of changes of belief: Accept 'If A then B' just in case revising your beliefs by A will result in believing B. Unfortunately, as Gärdenfors showed 30 years ago, this idea is at odds with prominent rationality postulates for belief revision. We analyse the problem and propose a solution, introducing one-shot and iterated belief revision along the way.

Le professeur Hans Rott (Regensburg) donnera quatre conférences à l'ENS dans le cadre d'une mobilité Erasmus+ et du programme "New Ideas in Mathematical Philosophy" (IEC-ENS) sur le thème de la révision des croyances. 

Les conférences du 2 et du 9 avril sont introductives et ouvertes à tous. Les conférences du 4 et du 12 avril sont sur des sujets plus avancés mais ne présupposent pas d'avoir assisté aux séances du 2 et du 9 avril. Les étudiants ou collègues intéressés de rencontrer Hans Rott peuvent contacter Rachel Dudley (rachel.elaine.dudley@gmail.com) pour fixer un RV avec lui.

Résumés des conférences :

2 & 9 April - 14:00-16:00, Salle Cavaillès, dans le cadre du cours "Croyance, conditionnels, fiction" (coordonné par Paul Egré et Louis Rouillé)

2 & 9 avril - "Conditionals and belief change" 
The Ramsey test specifies the meaning of conditionals in terms of changes of belief: Accept 'If A then B' just in case revising your beliefs by A will result in believing B. Unfortunately, as Gärdenfors showed 30 years ago, this idea is at odds with prominent rationality postulates for belief revision. We analyse the problem and propose a solution, introducing one-shot and iterated belief revision along the way.

4 avril - Séminaire Linguae, 11:30-13:00 - Salle L357/359, 24 rue Lhomond

Difference-making conditionals and the relevant Ramsey test*. Conditionals in natural language often express that the antecedent makes a difference for the consequent. A relevantised form of the Ramsey Test accounts for that. Most of the traditional axioms for conditional logic become invalid (as they should), but there is still an interesting logic of difference-making conditionals.

12 avril - 10:00-11:00 - 24 rue Lhomond, salle L357/L359, dans le cadre du colloque PALLMYR 

Probabilities, coherent belief and coherent belief change*. The lottery paradox teaches us that subjective probabilities (credences, degrees of belief) are difficult to harmonise with beliefs simpliciter. This talk presents a new suggestion of how to solve the problem by combining the Lockean thesis with a notion of coherence for belief. (Joint work with John Cantwell.)