Two Mistakes Regarding the Principal Principle

This paper examines two mistakes regarding David Lewis’ Principal Principle that have appeared in the recent literature. These particular mistakes are worth looking at for several reasons: The thoughts that lead to these mistakes are natural ones, the principles that result from these mistakes are untenable, and these mistakes have led to significant misconceptions regarding the role of admissibility and time. After correcting these mistakes, the paper discusses the correct roles of time and admissibility. With these results in hand, the paper concludes by showing that one way of formulating the chance–credence relation has a distinct advantage over its rivals. Introduction Background 2.1The chance function 2.2The chance–credence relation 2.3Assumptions Assessing the First Mistake 3.1The first mistake 3.2Motivating the first mistake 3.3Why the first mistake is problematic 3.4Consequences of the first mistake The Role of Admissibility 4.1Crystal balls 4.2Usefulness 4.3The strength of PP1 4.4Lewis and admissibility Assessing the Second Mistake 5.1The second mistake 5.2Motivating the second mistake 5.3Why the second mistake is problematic 5.4The role of time Assessing the Chance–Credence Relation 6.1Take I: Lewis' grounding argument 6.2Take II: general grounding arguments 6.3The winner