If I say we do not need theory to interpret history , how can it be that I also contend that Lincoln's diaries are not a simple statement of the"facts," but require interpretation? Interpretation based on what , if not a theory? Well, first of all, let us note that the term "theory" is overloaded. In one sense, we can use theory for something such as, "Well, I have a theory that Lincoln actually wanted to be martyred, which is why he went to the theater." Certainly historians must have "theories" like this, although I would prefer "hypothesis" here: they need to think about history, after all! What I mean by saying historians do not need "theory" (and what I believe Mises meant when he claimed they did ) is that they do not need what Aristotle would call theoria : abstract, general systems of timeless laws. For instance, Arnold Toynbee, in his A Study of History , develops a theory of how a civilization in decline wil...