 What good is appeal to history when it comes to evaluating the rationality of decisions and actions? Since the past is already over, isn’t history simply “bunk”? A couple of everyday locutions suggest otherwise. It is commonly held that “history” (meaning historiography, the disciplined study of what happened in history) is a debunker of myths. And politicians are not the only people worried about “the judgment of history”. Both these ideas came into play in the new historically-oriented philosophy of science that began to emerge at the end of the 1950s. The “new historicists” (as we may call them) included Thomas Kuhn, N.R. Hanson, Mary Hesse, Imre Lakatos, Paul Feyerabend, Stephen Toulmin, Dudley Shapere, Larry Laudan, Ernan McMullin, and Michael Ruse. They claimed that the then-dominant positivist and Popperian accounts of science were themselves bunk—myths about how science is done. Some new historicists claimed to find larger units and a hitherto unnoticed dynamic in the time-series of the historical record—long-term, forward-looking research programs that included evolving series of related theoretical moments. Above all, the historicists stressed the depth of major historical changes and the resulting challenges to cumulative scientific progress. They argued that there was nothing in the traditional “logic of science” that could rationalize such changes. The problem was to produce a new dynamical model of science that would capture these patterns and rationally motivate them.