The previous three chapters presented a sympathetic exposition of James's Master Syllogism. For it to work, we must not only be able to believe intentionally but do so freely in James's libertarian sense. James argued that we cannot determine on evidential grounds whether or not our wills possess such contra-causal freedom to determine the manner in which we are conscious, thus determining what we believe, which in turn will determine how we act. What justification, then, could we have for believing that we are free in this sense? James's answer is that we could have a pragmatic justification based on the desirable consequences of so believing. Whereas an evidential or, more generally, epistemic justification presents arguments directed at establishing the truth of the proposition believed, a pragmatic justification is directed at establishing the desirable consequences of believing this proposition. This chapter explores James's attempt to give a pragmatic justification for believing that our wills are free, as well as for believing other propositions that are of great importance to us, such as that God exists.

James's term for a pragmatic justification is a “will-to-believe” justification. The basic idea is that one is justified in believing, or getting oneself to believe, an evidentially undecidable proposition when doing so will have desirable consequences, that is, maximize desire–satisfaction over desire–dissatisfaction. The qualification “or get ourselves to believe” will be dropped hereafter for the sake of brevity.