"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 Obj. 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 Obj. 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." [2]

[2] Summa Theologica [I, Q. 1, Art. 2]