|Fr. Reginald Garrigou-Lagrange|
Theology is a science made possible by the light of revelation. Theology, therefore, presupposes faith in revealed truths. Hence the proper object of theology is the inner life of God as knowable by revelation and faith. By this object theology rises above metaphysics, which sees in God the first and supreme being, the author of nature, whereas theology attains God as God (sub ratione Deitatis).
How does theology differ from faith? The object of theology, in the theologian who is still viator, is not the Deity clearly seen, as in the beatific vision, but the Deity known obscurely by faith. Theology, then, is distinguished from faith, which is its root, because theology is the science of the truths of faith, which truths it explains, defends, and compares. Comparing these truths with one another, theology sees their mutual relations, and the consequences which they virtually contain. But to use this method for attaining its proper object, the inner life of God as God, theology must presuppose metaphysics which sees God as the Supreme Being. That this is the object of metaphysics is clear, we may note, from revelation itself. When God says to Moses: "I am who am," we recognize in those words the equivalent statement: God alone is subsistent existence.
Theology, therefore, though here below it proceeds from principles which are believed, not seen as evident in themselves, is nevertheless a branch of knowledge, a science in the proper sense of the word. The characteristic of science is to show "the reason why this thing has just these properties." Theology does just that. It determines the nature and properties of sanctifying grace, of infused virtue, of faith, of hope, of charity. St. Thomas, in defining theology, uses the Aristotelian definition of science which he had explained in his commentary on the Later Analytics. To know scientifically, he says, is to know this thing as what it is and why it cannot be otherwise. Theology then is a science, not merely in the broad sense of certain knowledge, but also in the strict sense of conclusions known by principles.
Such is theology here below. But when the theologian is no longer viator, when he has received the beatific vision, then, without medium, in the Word, he will behold the inner life of God, the divine essence. Then he will know, with fullest light, what before he knew by faith. And beyond that, extra Verbum, he will see the conclusions derivable from faith. In heaven, theology will be perfect, its principles evident. But here below, theology is in an imperfect state. It has not, so to speak, become adult.
Hence theology, as attainable here below, while it is a science, and is a sub-alternate science, resting on the mind of God and the blessed in heaven, is nevertheless, when compared with all merely human knowledge, a wisdom specifically higher than metaphysics, though not as high as the infused faith which is its source. Theology then, generated by the theological labor, is by its root essentially supernatural. If, consequently, the theologian loses faith (by grave sin against that virtue): there remains in him only the corpse of theology, a body without soul, since he no longer adheres, formally and infallibly, to revealed truths, the sources of the theological habit. And this is true, even if, following his own will and judgment, he still holds materially one or the other of these truths.