 One might object to Regularity on the ground that it is in conflict with Conditionalization. To see the conflict, note that conditionalization on a contingent proposition \(E\) drops the credence in another contingent proposition, \(\neg E\), down to zero. But that violates Regularity. In reply, defenders of Regularity can replace conditionalization by a generalization of it called Jeffrey Conditionalization, which need not drop any credence down to zero. Jeffrey Conditionalization will be defined and discussed in  section 5.3.