- 1 - Encoding The ATMS In AGM Logic ( Revised )

The two main theories of justification are the foundational theory and the coherence theory. We choose as representatives of these two theories the ATMS [de Kleer 1986] and the AGM logic [Gärdenfors 1988a], and show that it is possible to simulate the ATMS in the AGM logic by encoding the justificational information as epistemic entrenchments. The ATMS context changes are performed by AGM expansion and contraction operations. The algorithm for calculating these entrenchments is presented, followed by a proof that the AGM logic with these entrenchments is behaviourally equivalent to the ATMS.