 Marc Bloch (1953) provided a very simple and penetrating definition of history. History is "man in time". By this he meant that history is the product of human action, creativity, invention, conflict, and interaction. Bloch was skeptical about many other categories commonly used to analyze history—periods, epochs, civilizations, reigns, and centuries. Instead, he advocated for what can be called an "actor-centered" conception of history. If there are structures and systems in history, they depend upon the beliefs, attitudes, and actions of individual actors. If there are causes in history, they likewise depend upon the actions and interactions of human actors within a setting of humanly created institutions and norms. The task of the historian is to reconstruct the meanings, beliefs, values, purposes, constraints, and actions that jointly explain the moments of history, from the meaning of an ancient stele to the causes of the rapid defeat of France in 1940.