Abstract

In Newcomb's Problem, a lot of people choose the option of one-boxing. However, the equivalent choice is rarely made in other similar decision problems. This discrepancy needs explaining. In this thesis, I consider Horwich's suggestion that evidential decision theory provides an explanation. Horwich argues that evidential decision theorists make these different choices because static screening cannot be used in Newcomb's Problem, yet it can be used in other similar decision problems. I discuss and expand upon his argument. I then describe the process of dynamic screening. The appeal to dynamic screening purports to show how screening could occur in Newcomb's Problem and thus lead evidential decision theorists to two-box. However, I argue that dynamic screening would not convince an evidential decision theorist to two-box, since the argument behind dynamic screening presupposes the irrationality of evidential decision theory. I then argue that using static screening also presupposes the irrationality of evidential decision theory. Thus, Horwich's argument is flawed. Screening cannot occur in any common cause problems, and the evidential decision theorist would be expected to do the equivalent of one-boxing. Evidential decision theory cannot explain why agents do the equivalent of two-boxing in some decision problems, and yet one-box in Newcomb's Problem.