Deontic obligations in justification logic

This thesis consists of two main chapters which connect two areas of deontic logic and justification logic. Deontic logic is logic of normative concepts, where the deontic reading of modal operator for □A is as "A is obligatory". On the other hand, justification logics replace an explicit term with modal operator such that instead of □A, justification logics features formulas of the form t : A, read as "A is justified by reason t", or "A is obligatory for the reason t", in deontic context.
In the second chapter, we focus on the category of non-normal modal logics and provide an explicit version of two logics in this category, the weakest non-normal modal logic E and logic EM, which is an extension of logic E by adding rule of monotonicity.
The main motivation for this attempt is raised from the following arguments initiated in the area of deontic logic. First, we consider paradoxes raising from deontic interpretation of modal operator in normal modal logic, which leads us towards non-normal modal logics.
The second issue is hyperintensionality. Considering the fact that deontic modals are hyperintensional, i.e., they can distinguish between logically equivalent formulas, one can see that traditional modal logic cannot provide an appropriate formalization of deontic situations. Since justification terms are hyperintensional in nature, we introduce novel justification logics as hyperintensional analogues to non-normal modal logics. We establish soundness and completeness with respect to various models and we study the problem of realization.
In the third chapter, we focus on conditional obligations in deontic logic. We review standard deontic logic and the well known Chisholm's puzzle confronting this system. For this reason, we turn into dyadic deontic logic which is often argued to be better than standard deontic logic at representing conditional and contrary-to-duty obligations.

2023

dissertation

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