Is there a Fitch style system that works with some of the modal logics? My prof taught us to use trees to prove modal logic arguments. Trees seem to provide a more efficient way to test arguments than Fitch does. However, I find that trees generally, and alethic (modal) trees especially, don't read as elegantly as the methods that resemble Fitch. Can Fitch, or a system that resembles it, accommodate any of the modal logics (i.e. Alethic, temporal, deontic, etc.)? If so, is there a resource that explains how to use the system to prove modal logic arguments? Thank you, -Hal

There are Fitch systems for about twenty different modal logics described very briskly here





More than enough to be going on with, I guess!

More expansively, Garson's good and accessible book _Modal Logic for Philosophers_ (CUP) introduces Fitch style systems for modal logics.