 The numbering is AGM’s, the names are due to Hansson (1999). Postulates (\(*\)3) and (\(*\)4) taken together say that if the input \(A\) is consistent with the belief set \(K\), then the background logic alone is sufficient to guide belief revision. When (\(*\)1) and (\(*\)2) are present and \(\iCn\) is a monotonic consequence operation, (\(*\)4) is equivalent to the Preservation Principle stating that if \(A\) is consistent with \(K\), then all elements of \(K\) are preserved in \(K*A\):