Ranking Functions, AGM Style

Wolfgang Spohn

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Keywords: Ranking Functions, (iterated) Belief revision, (iterated and multiple) Belief contraction, (conditional) Dependence and independence

: First, ranking functions are argued to be superior to AGM belief revision theory in two crucial respects. Second, it is shown how ranking functions are uniquely reflected in iterated belief change. More precisely, conditions on threefold contractions are specified which suffice for representing contractions by a ranking function uniquely up to multiplication by a positive integer. Thus, an important advantage AGM theory seemed to have over ranking functions proves to be spurious.

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Wolfgang Spohn,


Spinning Ideas, Electronic Essays
Dedicated to Peter Gärdenfors on His Fiftieth Birthday