  Bonaventure does not explicitly address the principles of theology. But he further clarifies its “subject” in a way that points to those principles. To faith, Scripture adds the notion of “authority,” and to the faith and authority of Scriptural revelation, theology adds “proof.” Theology presupposes faith but adds to it rational demonstrations about matters of faith. Consequently, Bonaventure adds a telling qualification to his description of the subject of theology. Theology’s subject is the object of belief “in so far as the believable is transformed into the notion of the intelligible, and this happens by the addition of  reasoning.”[12]  With this concise formula, Bonaventure includes within theology both religious belief transformed by arguments from natural reason and natural reason transformed by arguments based on religious revelation. If so, then theology must have the kinds of principles that make possible both kinds of arguments: the fundamental truths of faith drawn from the Bible and tradition, but also fundamental truths of reason. What makes all such basic truths theological is their argumentative function. Theological arguments may draw from revelation by using revealed truths as premises and they may draw from reason by using rational truths as premises. Both kinds of arguments are theological because of the use to which they are put. In this way, philosophical reasoning has an integral place within the domain of Bonaventurean theology.