A Theory of Plausibility

• Applicant: Professor Dr. Hans Rott
• Subject Area: Theoretical Philosophy
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 444804884

The traditional problem of information scarcity calls for methods of defeasible reasoning (default reasoning, "non-monotonic" reasoning). The more recent problem of information overload, which has become particularly pressing in our "post-truth era", calls for methods for the rational revision of beliefs and opinions. I want to show that a theory of plausibility offers the resources that are needed to cope with both the problem of information scarcity and the problem of information overload. I aim at putting "plausibility" on the map of fundamental philosophical terms.The intended monograph aims at developing a comprehensive philosophical theory of plausibility that unifies a model for beliefs and a model for expectations within a single mode of representation. It covers, among other things,(i) the representation of beliefs and belief states;(ii) the philosophy underlying defeasible reasoning and belief revision, interpreting plausibility as doxastic preference;(iii) rational `doxastic choices' in the face of imperfect discrimination (indistinguishability, negligibility), incomparability (incommensurability, multi-dimensionality) and context effects;(iv) reflections on the relation between qualitative representations of cognitive states and quantitative representations as well as their dynamics.The approach of the project is decidedly qualitative; it covers categorical belief and categorical expectation as well as comparative strengths of belief and expectation. However, quantitative representations (probabilities, rankings) will also be discussed that help us understand the status of important principles of the qualitative side.

• DFG Programme: Research Grants