What do the ¯elds of astronomy, economics, ¯nance, law, mathematics, med- icine, physics, and sociology have in common? Not much in the way of sub- ject matter, that's for sure. And not all that much in the way of methodology. What they do have in common, with each other and with many other ¯elds, is their dependence on a certain standard of rationality. In each of these ¯elds, it is assumed that the participants can di®erentiate between rational argu- mentation based on assumed principles or evidence, and wild speculation or nonsequiturs, claims that in no way follow from the assumptions. In other words, these ¯elds all presuppose an.
