 Reflection says that my current self’s degree of belief in q given that my future self will believe it to degree x should be x. It is implied by the fact that her degrees of belief are represented as probabilities that my future self is coherent, but that alone does not rule out the possibility that her judgment is compromised in some other way—as for example when Ulysses anticipated that he would be entranced by the Sirens—and the principle can be questioned for such cases (Sobel 1987; Christensen 1991; van Fraassen 1995). However, the self-doubt we are imagining is one that the subject has about her current beliefs, and the synchronic version of Reflection