Affiliations: Computer Science, CUNY Graduate Center, 365 Fifth Avenue, New York, NY 10016, USA. rwang@gc.cuny.edu
Note: [] Address for correspondence: Computer Science, CUNY Graduate Center, 365 Fifth Avenue, New York, NY 10016, USA
Abstract: It is well known that Modal Epistemic logic (MEL) suffers from the problem of logical omniscience. In this paper, we will argue that in order to solve the problem, the temporal dimension of knowledge has to be revealed and following this analysis, we present a general epistemic framework, timed Modal Epistemic Logic (tMEL), modified from MEL, such that the time at which a formula is known by an agent based on his reasoning procedure is explicitly stated. With the help of the additional temporal devices, we are able to determine what is actually known by the agent within a reasonable time of reasoning. The discussions will focus on tS4, the tMEL counterpart of S4, but the method can be uniformly generalized to the study of other tMEL logics. Both the semantics and axiomatic proof systems will be provided, accompanied by soundness and completeness results, and other technical features of tMEL are also examined. This work originates from the study of Justification Logic, which shapes many aspects of this paper, and is also a direct response to the request to utilize the use of awareness functions such that time can be added to the picture. A generalized awareness function is employed in the semantics to trace when a formula is deduced.
