How does a gracious God save stubborn sinners? We cannot answer this question without delving into two of the most challenging and hard-fought doctrines in Christian theology: predestination and justification. Both doctrines played a crucial role in the Protestant Reformation, provoking conflicts not merely between the Reformers and Rome but also within the ranks of each. As a deeply Augustinian theologian, trained in one of the leading Catholic universities before converting to Protestant teaching, few men in the sixteenth century were so well-equipped to address these difficult subjects as Peter Martyr Vermigli.