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Maximal Deontic Logic

Friday, November 10, 2023, 11:00 am – 12:30 pm

This talk is planned as an in-person event. Registration is only required for non-CEU members. 


The worlds accessible from a given world in Kripke models for deontic logic are often informally glossed as ideal or perfect worlds (at least, relative to the base world). Taking that language seriously, a straightforward but nonstandard semantic implementation using models containing maximally good worlds yields a deontic logic, MD, considerably stronger than that which most logicians would advocate for. In this talk, I examine this logic, its philosophical significance, and its technical properties, as well as those of the logics in its vicinity. The principal technical result is a proof that MD is pretabular (it has no finite characteristic matrix but all of its proper normal extensions do). Along the way, I also characterize all normal extensions of the quirky deontic logic D4H, prove that they are all decidable, and show that D4H has exactly two pretabular normal extensions.


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