“Science: The Only Means of Knowledge”
In Aquinas’ The Nature and Extent of Sacred Doctrine, he deals with ten points of inquiry. First, he answers the view that philosophical science is the only means we need to get at knowledge, because to seek anything above reason is prohibited (Ecclus.3: 22). Moreover, knowledge is grounded in ontology, even the knowledge of God. Aquinas points out that inspired Scripture (2 Tim.3: 16) instructs us in the knowledge of God, the grounds of which is not human reason, but divine revelation. It is specifically sacred doctrine that is necessary for salvation. Again, Aquinas understands that natural and sacred theology, have their respective means of discovery and their epistemic complementary value.
“Sacred Doctrine Cannot Be Science”
Second, there is the objection that sacred doctrine cannot be science for all sciences come from self-evident principles, whereas sacred doctrine proceeds from articles of faith, which are not self-evident nor do all men accept them (2 Thes.3: 2). Furthermore, science deals with facts and does not concern itself with personal biography, as does sacred doctrine. Aquinas references Augustine and asserts that sacred doctrine is the only science that begets saving faith. It not only nourishes and protects said faith, but it also strengthens it. We must also remember that two kinds of science obtain; the science that is known through the natural light of intelligence (i.e., arithmetic or geometry), and that which proceeds from the higher light of science (i.e., the science of God). Moreover, the principles of any science are self-evident or can be reduced to the conclusions of higher science. Again, the principal reason individual facts are treated in sacred doctrine, are for moral exhortation, so that the authority of the men handing down divine revelation may be established.
“Sacred Doctrine Cannot Be One Science”
Third, there is also the view that sacred doctrine cannot be one science, because science treats only one class of subjects, whereas sacred doctrine considers both creator and creature. Hence it cannot be one science. However, Aquinas asserts that sacred doctrine primarily focuses on God, and on his creatures secondarily, so far as to accentuate God as their originator and sustainer. Aquinas appears to have a more integrative approach to science.
Other issues Aquinas tackles considers whether or not sacred doctrine is speculative or practical, whether it is the same as wisdom, whether it is a matter of argument, how it is compared with other sciences, etc
 St. Thomas Aquinas: The Summa Theologica, Translated by the Fathers of the English Dominican Province, (Benzinger Bros. Edition, 1947).