 The successes of natural theology, for Aquinas, have their limit. For although natural reason can establish the existence of a perfect being, it is incapable of establishing many of the features that distinctively characterize the Christian God, such as God’s triune nature and God’s incarnation as a human being. Here is a place where philosophy alone, unaided by revelation, fails to yield an adequate theology. Since the ultimate goal of human life, salvation in the life to come (§8.1), requires some grasp of these Christian truths, “it was necessary for the sake of human salvation that certain truths that surpass human reason be made known to us through divine revelation” (ST 1a 1.1). The study of revealed theology is important, moreover, not only with respect to these so-called mysteries of the faith, but also in cases where the results of natural reason are too precarious to be counted on. Without direct access through revelation, “the truth about God investigated by reason would be available only to a few people, after a long time, and with the admixture of many errors.” Accordingly, “beyond the philosophical disciplines investigated by human reason, it was necessary to have a sacred teaching through revelation” (ibid.). This sacred teaching (sacra doctrina) is the work of theology.