Context Dependence of Epistemic Operators in Dynamic Evidence Logic Irma Cornelisse Abstract: In this thesis it is argued, supported by the relevant alternatives theory, that epistemic operators are context dependent. They are context dependent, in the sense that the context filters out certain irrelevant alternatives from the information state of an agent. As a consequence, rational knowledge and rational beliefs are evaluated on only a subset of the information state of the agent. This filtering process of the context origins from the fact that an agent is not in all circumstances capable of overseeing every possible alternative. The alternatives an agent is capable of overseeing are determined by the context. Furthermore, a concrete proposal of an epistemic logic that incorporates this context dependence of epistemic operators will be given. This proposal is an extension of the evidence logic of Johan van Benthem and Eric Pacuit, which basically is an epistemic logic where beliefs are formed on the basis of evidence in the agent’s information state. In this proposal, called contextual evidence logic, beliefs are formed on the basis of the relevant evidence in the agents information state. Again, the relevance of the evidence is determined by the context. Moreover, some characteristics will be exploited, the contextual evidence logic will be made dynamic in order to incorporate dynamic context changes. Finally, natural examples, of contextual influence on rational beliefs and how the contextual evidence logic will deal with this, will be provided. Key words: dynamic epistemic logic, context, epistemic operators, relevant alternatives theory, evidence