Historiographic reasoning from evidentiary inputs is sui generis. Historiography is neither empirical, nor self-knowledge, nor a genre of fiction or ideology. Historiographic reasoning is irreducible to general scientific or social science reasoning. The book applies Bayesian insights to explicate historiographic reasoning as probable. It distinguishes epistemic transmission of knowledge from evidence from the generation of detailed historiographic knowledge from multiple coherent and independent evidentiary inputs in three modular stages. A history of historiographic reasoning since the late 18th century demonstrates that there was a historiographic scientific revolution across the historical sciences in the late 18th and early 19th centuries. The underdetermination of historiography by the evidence, counterfactual historiographic reasoning, and false reasoning and other fallacies are further explained and discussed in terms of the probabilistic relations between the evidence and historiography.