  To understand theology as a “science” making faith intelligible, Bonaventure must clarify its material cause. Determining that material cause of theology is the same as settling on its subject. On this point, there had been considerable dispute among the Masters. Aristotle’s “sciences” were all limited to a particular genus, such as “animal” or “soul” or “memory” or “ethics.” Even his universal science of metaphysics was limited to studying substances; it eschewed the other categories. Theology, by contrast, cuts across all genera and includes God, who is not confined within any genus. Bonaventure was familiar with many accounts of the subject of theology: “things and signs,” the work of “reparation for sin,” “Christ—head and members,” “God,” and “the object of belief” (credibile). To throw light on these conflicting answers, Bonaventure turned to his study of the Arts. Priscian had noted three different senses of the subject of grammar. Its subject in the sense of its “root principle” is the “letter” that makes up words; its subject conceived as an “integral whole” is “a fitting and complete oration;” and its subject conceived as “universal whole” is “meaningful sound, articulated and ordered.” There are three correlative senses of the subject of theology: “God” is the “principle” of the subject and “Christ—head and members” is the “integral whole,” the entirety of what theology studies. But the most important sense of “subject” is the “universal whole.” Therefore, “the subject of this book, properly speaking,” is the “object of belief,” a subject that lets theology range over all realities and all thoughts about which one can have religious faith.