From Iterated Revision to Iterated Contraction

Jake Chandler (La Trobe University)

Jake Chandler (La Trobe) will give a talk titled "From Iterated Revision to Iterated Contraction". This talk is joint work with Richard Booth (Cardiff). 

Abstract: While a substantial body of research has now accumulated on the problem of iterated belief revision, work on the parallel problem of iterated contraction remains comparatively underdeveloped.

One obvious way to level out this discrepancy would be to introduce a bridge principle that enables us to derive, from constraints on iterated revision, corresponding constraints on iterated contraction. But while there exists a well known and widely accepted postulate connecting single-shot revision and contraction, namely the ‘Harper Identity’, there has been no suggestion to date as to how to extend this principle to the iterated case.

After noting that the problem at hand is essentially one of aggregating a pair of preference relations, we consider a new family of binary preference aggregators, (a) whose characteristic properties enable us to derive some noteworthy results regarding iterated belief change and (b) whose extension to the n-ary case may also be of potential interest in the field of social choice.