Beyond Foundational Reasoning

Implementations of logical reasoning systems are invariably based on the foundational theory of justification. The AGM logic is based on the coherence theory and the principle of minimal change, but this presents difficulties in its implementation. We show that both the foundational and coherence styles of reasoning are necessary for practical reasoning and that both can be achieved in the AGM logic by choosing particular epistemic entrenchment orderings. We also describe the limitations which must be imposed on the logic in order to implement the system.