 The student’s formation of a new, initial credence in the new theory seems to pose a relatively little threat to the Principle of Conditionalization, which is most naturally construed as a norm that governs, not credence formation, but credence change. So the more serious problem lies in the student’s change of her credence in the old theory. If this credence drop really results from conditionalization on what was just learned, \(E_\textrm{logical}\), then the credence in \(E_\textrm{logical}\) must be boosted to 1 from somewhere below 1, which unfortunately never happens. So it seems that the student’s credence drop violates the Principle of Conditionalization and rightly so, which is known as the problem of new theory. The following presents two reply strategies for Bayesians.