S5 solution to the red hat puzzle
Robert C. Robinson · Disputatio · 2007
Abstract I argue that the solution to the Red Hat Problem, a puzzle derived from interactive epistemic logic, requires S5 . Interactive epistemic logic is set out in formal terms, and an attempt to solve the red hat puzzle is made in K τσ , K ρτ , and K ρσ , each of which fails, showing that a stronger system, K τσρ is required.