Objection 1. It seems that sacred doctrine is not a science. For every science proceeds from self-evident principles. But sacred doctrine proceeds from articles of faith which are not self-evident, since their truth is not admitted by all: "For all men have not faith" (2 Thessalonians 3:2). Therefore sacred doctrine is not a science.
Objection 2. Further, no science deals with individual facts. But this sacred science treats of individual facts, such as the deeds of Abraham, Isaac and Jacob and such like. Therefore sacred doctrine is not a science.
On the contrary, Augustine says (De Trin. xiv, 1) "to this science alone belongs that whereby saving faith is begotten, nourished, protected and strengthened." But this can be said of no science except sacred doctrine. Therefore sacred doctrine is a science.
I answer that, Sacred doctrine is a science. We must bear in mind that there are two kinds of sciences. There are some which proceed from a principle known by the natural light of intelligence, such as arithmetic and geometry and the like. There are some which proceed from principles known by the light of a higher science: thus the science of perspective proceeds from principles established by geometry, and music from principles established by arithmetic. So it is that sacred doctrine is a science because it proceeds from principles established by the light of a higher science, namely, the science of God and the blessed. Hence, just as the musician accepts on authority the principles taught him by the mathematician, so sacred science is established on principles revealed by God.
Reply to Objection 1. The principles of any science are either in themselves self-evident, or reducible to the conclusions of a higher science; and such, as we have said, are the principles of sacred doctrine.
Reply to Objection 2. Individual facts are treated of in sacred doctrine, not because it is concerned with them principally, but they are introduced rather both as examples to be followed in our lives (as in moral sciences) and in order to establish the authority of those men through whom the divine revelation, on which this sacred scripture or doctrine is based, has come down to us.
Source: Summa Theologica (New Advent)