This chapter continues the exploration of the development of the doctrine of justification during the Middle Ages, focussing on the question of how sinners are able to appropriate justification. The chapter opens by considering the nature of the human free will (liberum arbitrium), a question discussed by Augustine, but which was found to require further conceptual development in the light of ambiguities and lack of precision at certain points. One of the questions regularly raised for discussion in the early medieval period concerned whether some form of predisposition for justification was required, and how this was to be correlated with the compromised capacities of fallen humanity. This chapter considers the debates within medieval theology over the the necessity and nature of the proper disposition for justification, which often centred on the question of the relation of human and divine contributions to the process of justification. Finally, the chapter considers the origins and application of the medieval theological axiom facienti quod in se est Deus non denegat gratiam (‘God does not deny grace to anyone who does their best’).