Objective chance, or the “big bad bug” of David Lewis's account of Humean Supervenience forces, as is well known, is a modification of the Principal Principle. Here, I argue that standard assumptions regarding conditional probabilities entail several puzzling consequences for Lewis's New Principle, namely, an apparent requirement to account for the chance of a theory of chance. These problems, I argue, cannot be adequately answered within the received framework, and so I suggest that an interpretation of conditional probabilities in terms (...) of Alan Hájek's recent work might go some distance toward their resolution. (shrink)