Abstract

Although written long before, in 2012 a work by Prior presenting a system that was able to demonstrate Hintikka’s theorem was published. Maybe one of the most relevant elements of that system is an axiom that clearly relates necessity, and hence modal logic, to obligation, and hence deontic logic. This paper analyzes that axiom based upon Carnap’s method of extension and intension in order to show that it should be accepted. Thus, the paper is intended to give further evidence supporting not only the aforementioned axiom, but also Prior’s system in general and, accordingly, Hintikka’s theorem.