 5. Historical content of theory of justification: The complexity of history. History is too complex and too subtle to be captured by a fixed, formal system or in terms of the dynamical relationships of a set of “state variables”. Logical and probabilistic systems alone are crude tools for capturing the reasoning of real people, scientists included. Besides the subtle, contextual reasons, innovative scientists work at moving research frontiers (“context of discovery”) and, so, must make many decisions under uncertainty (not only under mere risk). Rationality has more to do with appropriate response to change than with sticking rigidly to one’s initial standpoint. This challenge strikes at the heart of traditional accounts of context of justification, hence at the heart of traditional philosophy of science. Thinkers from Kuhn to van Fraassen (2002: 125) have taken a dim view of confirmation theory, although Bayesians have made valiant attempts to capture historicist insights. (For examples, see Salmon 1990 and Howson &amp; Urbach 1993).