 The second step, rescaling, deserves attention. It is designed to ensure compliance with Probabilism, but it also has an independent, intuitive appeal. Consider any two possibilities in which new evidence E is true. Thus the new evidence alone cannot distinguish those two possibilities and, hence, it seems to favor the two equally. So it seems that, if a person starts out being twice as confident in one of those two possibilities as in the other, she should remain so after the credence change in light of E, as required by the rescaling step. The essence of conditionalization is preservation of certain ratios of credences, which is a feature inherited by generalizations of conditionalization (see  section 5  for details).