Abstract This article examines historicism as the expansion of historiography beyond its bounds, analogous to Physicalism, Naturalism, Psychologism, and Scientism. Five senses of historicism are distinguished: Ontological Historicism claims ultimate reality is, and only is, historical. Idiographic historicism considers historiography an empirical science that results in observational descriptions of unique singular events. Introspective historicism considers the epistemology of historiography to be founded on self-knowledge. Scientistic historicism considers historiography an applied psychology or social science that can expand to overtake the social sciences. Methodological historicism extends the use of historiographic methodologies to unreliable or dependent evidence. The first four historicisms are inconsistent with historiography within bounds and implode. Methodological historicism describes proper historiographic methodologies that are applied out of their proper bounds, but are used in historiography based on the epistemology of testimony and the tracing of the transmission of information from historical event to historiographic evidence.