- Analytical philosophy
- Philosophy not elsewhere classified
- Mathematical logic and foundations
- Philosophy of law
A practical reason is a consideration in favor of why something is obligatory. Since reasons are central both in everyday normative reasoning and in normative theorizing, having precise models of how reasons are structured and how to reason with them is crucial to advance our understanding of substantive normative questions. The general aim of this project is to investigate the structure of practical reasons, which has so far been missing. This aim will be realized by giving a unified formal account of the aggregation and subtraction of reason content, and of partial reasons. This account will serve as the semantic backdrop to construct natural logical systems to reason with reasons, based on justification logic with a novel truthmaker semantics. Most of the existing literature uses reasons in a merely instrumental way, focusing just on the deliberative process rather than on reasons themselves, and treats them as atomic. This flatness, coupled with largely intensional approaches, causes relevance problems and in many cases makes it impossible even to explore certain issues (double counting, subtraction, partial reasons). Having logical systems based on finer-grained structures for reasoning with reasons, however, makes it possible to investigate not only the structural assumptions we make when we reason practically, but also the more unintuitive consequences of our normative stances. In general, this project will contribute to the progress of formal ethics and of logic.