Consistent Belief Reasoning in the Presence of Inconsistency

Since everything is a consequence of an inconsistency, classical logics are not useful in modeling the reasoning of an agent who has inconsistent beliefs. In this paper, we differentiate consistent beliefs from inconsistent beliefs. We propose two belief operators Bc and B, standing for consistent belief and belief, respectively. Bc has the modus ponens property, by which the agent is able to reason with consistent beliefs as normal and draw consistent conclusions. B tolerates inconsistency, and by B the agent can reason about his inconsistent beliefs as well. The concept of consistent belief and our logical formalism for it are new, in that reasoning consistently about the information in an inconsistent knowledge base is possible. We also present a complete axiomatization for the logic and discuss the application of Bc and B in reasoning about implicit knowledge in a group of agents and eliminating inconsistency from a knowledge base.

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