In ‘Belief and the Will’ van Fraassen (1984: 255) argues that traditional epistemology allows one to believe in propositions that are not entailed by the evidence at hand, while at the same time acknowledging that what is taken to be evidence may in fact turn out to be false. However van Fraassen (1984) shows the incoherence in such agent’s belief states by a diachronic Dutch Book argument, in which such agents are shown to be vulnerable to sure losses in sets of wagers which he regards as fair, which deems him as irrational. As a solution to this problem, van Fraassen (1984) formulates the Reflection Principle as a further constraint for rational agents’ credences. In this thesis I will critically evaluate the Reflection Principle as a constraint for rational agent’s credences, and conclude that the Reflection Principle as an attack and solution to the traditional epistemological view is unsuccessful since it is incompatible with epistemic agency.