Degrees of Influence and the Problem of Preemption

Cei Maslen
Florida State University

This paper is an investigation into the notion of degree of influence, and its application to the problem of preemption. 

In "Causation as influence", Lewis presented a new account of causation under determinism, and some new observations on the problem of preemption. He claimed that, in cases of preemption, the preempting cause is much more of a cause than its preempted alternative; it has much more influence. 

I begin by trying to make sense of the notion of degrees of influence.  Then I emend Lewis's approach to preemption in response to objections, compare it to Kvart's Sustainably Reducible Influence account, and finally conclude that all these accounts fail to solve the problem of preemption.