 Theorem. Suppose that \(*\) is a revision operation for \(\bB\) satisfying all eight revision postulates. Then, the non-nonmonotonic consequence relation given by \(\alpha \dproves \beta \text{ iff } \beta \in \bB * \alpha\) satisfies all the principles of System R. Conversely, suppose that \(\dproves\) is a consequence relation that satisfies all the principles of System R. Then, the revision operation \(*\) defined letting \(\bB = \{ \alpha : \top \dproves \alpha \}\) and \(\bB*\alpha = \{ \beta : \alpha \dproves \beta \}\) satisfies all eight revision postulates.