 The idea behind this equation is that the agent revises by \(\alpha\) by first clearing from her belief set anything less entrenched than \(\neg \alpha,\) (by dominance, this includes everything entailing \(\neg \alpha\)), adding \(\alpha\), and then closing under logical consequence. Gärdenfors and Makinson (1988) prove that this definition gives rise to a revision operator satisfying AGM*1–8 and, conversely, that every revision operator satisfying AGM*1–8 can be seen as arising from some entrenchment order in this way. These results illustrate why AGM theory is not a theory of iterated revision: the revision operation takes as input an entrenchment order and belief state, but outputs only a belief state. That severely underdetermines the results of subsequent revisions. 