 Cal and Re-Cal give an explicit characterization of self-doubt and justification of a unique and determinate response to it on the basis of deeper principles that are compelling independently of the current context. Cal follows from only two assumptions, first that probabilistic coherence is a requirement of rationality, and second that rationality requires one’s credences to align with what according to one’s evidence are the objective probabilities. Re-Cal comes from further assuming that updating our beliefs should occur by conditionalization.