Justification Logic (JL)

Lecture number: 101191-HS2018-0
Start: 2018-09-18
End: 2018-12-18
Venue: Hörraum B077, ExWi, Sidlerstrasse 5
Lectures take place on:
  • Tuesday from 09:15 to 12:00


Justification logics are closely related to modal logics and can be viewed as a refinement of the later with machinery for justification manipulation. Justifications are represented directly in the language by terms that can be interpreted as formal proofs in a proof system, evidence for knowledge, winning strategy in a game, etc. This more expressive language proved beneficial in both proof theory and epistemology and helped investigate problems ranging from a provability semantics for intuitionistic logic to the logical omniscience problem. It has connections with intuitionistic logic, lambda calculus, epistemic logic, provability logic, and structural proof theory. Justification logic is a new and fast evolving field that offers unexpected results and insights into old problems. Its position at the junction of mathematics, philosophy, and computer science makes it of interest to a wide audience.

We plan to discuss the following topics:

  • Relationship between modal and justification logic; justification extraction
  • Formal semantics for representing justifications
  • Quantitative approach to the logic omniscience problem
  • Self referential proofs in modal logic
  • Philosophical puzzles and paradoxes about knowledge (e.g. Gettier examples)
  • Common knowledge and multi-agent systems

After this course, students will be able to:

  • describe various model constructions for justification logics including modular models, fully explanatory models, and generated models
  • establish decidability of justification logics
  • describe complexity bounds for justification logic
  • explain the connection between modal logic and justification logic
  • apply justification logic to study philosophical puzzles and paradoxes about knowledge (e.g. Gettier examples)
  • discuss the feasibility approach to the logical omniscience problem
  • explain self-referentiality in the context of modal and justification logic