  Since science exists as an intellectual habit in the mind of the knower, the efficient cause of any book of theology is the author who wrote it, Peter Lombard in the case of his Sentences, Bonaventure himself in the case of his commentary. Lombard was no mere scribe, compiler, or commentator; he was an “author,” and the same is true of Bonaventure himself. This simple point distinguishes faith, whose sole efficient cause is God working through grace, from both philosophy and theology, whose efficient cause is the human mind, though even here God has a role to play.