A temporal dynamic deontic logic

This paper presents a formalization of refraining from actions and a deontic logic based on a process logic. The notion of refraining is needed to handle obligated actions. To refrain to do an action is to do something else. The process logic used is a mix of dynamic logic and temporal logic: actions in it are interpreted as sets of paths and temporal formulas describe the process of performing actions. The deontic logic has a temporal propositional constant saying that a bad thing will be done in the next moment. Normative properties of actions can be defined according to what happens in the process of performing actions

How Knowledge Affects Obligations:a Study on the Logic of Knowledge-Based Obligations

A doctor generally does not have an obligation to treat a person if the doctor does not know that he/she is ill. But when the doctor knows the person is ill, the doctor ought to treat him/her. So what we ought to do depends a lot on what we know at that moment. This thesis provides a logical formalization of the concept of knowledge-based conditional obligation which paraphrases `A ought to be achieved by an agent under the condition that he/she knows B'. This notion is characterized by a sound and strongly complete axiomatization in this thesis. Furthermore, the framework is dynamified in order to show how knowledge change affects obligation change. Accordingly, those situations where agents' obligations are updated by their dynamic information can be modelled. Besides information change, norm change may also lead to new obligations. The notion of relativized conditional obligations is proposed for conceptualizing obligations induced by different normative systems. Several types of updates on normative systems are studied. They bring about new obligations or defeat original obligations in different ways. In the final chapters, this thesis jumps out of the approach of `ought-to-be' obligations and conceptualizes the notion of knowledge-based `ought-to-do' obligation based on dynamic epistemic logic. The basic idea of defining this notion is that an action ought to be done if and only if the action always improves the initial situation to a better situation. A sound and strongly complete axiom system is also established