The sixteenth-century Reformation in Germany is often viewed as having made a radical change by breaking with the thinking of the past and starting something new. One example given is the Reformation's perceived rejection of philosophy (that is, philosophy's method, subject matter, and purpose), although the regard for philosophy has often been assessed only on the basis of second-order data. Past research has looked at various individuals' keeping or breaking with the preceding era and at the question of continuity between individuals within the Reformation movement of the sixteenth century. This interdisciplinary study examines the regard for philosophy and both the keeping and breaking of the whole movement, by considering how philosophy is used in The Book of Concord, which contains Reformation documents from the earlier and later sixteenth-century that were widely accepted and given authoritative status. The specific Book of Concord uses of philosophy considered are second-order statements about philosophy and its cognates and about logic, as well as first-order uses of organization by [ancient Greek topoi] ("topics") or loci ("places") and of argumentation by both induction (namely, example and analogy) and deduction. The study's taking philosophical uses as indicators of regard for philosophy has been called for in previous research and is relatively unique. Another significant contribution of this study is a detailed treatment of syllogisms used in arguing, for example, for the Reformers' position that justification, or righteousness before God, is only on account of faith in Jesus Christ. The study also considers the Reformers' formal distinction between justification and sanctification, or holy living, as a case study for philosophy in service to theology as its handmaiden in a ministerial role. More than finding an inexplicable, eclectic use, the dissertation concludes that The Book of Concord where necessary rejects philosophy and logic but nevertheless at the same time makes use of them, except where the use of such methods contradicts or goes beyond the Reformers' understanding of God's revelation in the Bible. Such rejection but simultaneous use both keeps and breaks with the preceding medieval period and continuous within the Reformation movement of the sixteenth century.