Paraphrasing the Summa: First part, Question 1, Article 2

 Question 1: The nature and extent of Sacred Doctrine

Is Christian doctrine of God?  Does Christian Doctrine teach us about heavenly things?

Article 2. Whether sacred doctrine is a science?

Is Christian doctrine a study of  heavenly principles?

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.

No, Christian doctrine is not a science.  Since Christian doctrine is above reason and many men do not believe it, then it is not a human study.  Therefore, it should not be taught as though it is a true body of knowledge, that is, a science, since it can not be proved.

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.

A science deals with general principles of the world, such as thermodynamic laws, mathematical equations, and movements of the stars.  But Christian doctrine is about the lives of certain important characters.  Therefore, it is more of a historical discipline, than 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.

The opposite is true.  St. Augustine of Hippo, a great doctor of the Christian faith once said that Christian doctrine teaches the general principles of salvation.  It is the only body of knowledge dedicated to this purpose and is therefore 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.

Furthermore, I add Christian doctrine is a science because there is more than one kind of science.  There are the sciences which teach the general principles of the natural world, such as arithmentic and geometry.  And then, there are the sciences which seek to explain the arts.  These are higher sciences which move beyond but do not contradict the principles we learned from arithmetic and geometry.

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.

So, Christian doctrine comes to us from God and from God's prophets. But just as musicians accept mathematical principles.  So, Christian doctrine depends on those principles of our faith 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.

The first objection stated that all sciences proceed from self evident truths.  St. Thomas disagrees with that idea.  Some sciences proceed from principles which are not self evident to many men because they are higher sciences.  This is the case with Christian 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.

The second objection states that Christian doctrine is not a science because it deals with certain people's lives.  St. Thomas says that these lives are provided as examples of the principles which we must hold in order to be saved and in order to provide the reasons why we must obey those through whom God's truths were passed down.