Whether Sacred Doctrine is a Single Science
We proceed to the third article thus:
1. It seems that sacred doctrine is not a single science. As the philosopher says: |one science treats of one kind of subject only| (I Post. An., Text 43). Now sacred doctrine treats of the Creator and also of creatures, and these do not belong to one kind of subject. Hence it is not a single science.
2. Again, sacred doctrine treats of angels, of creatures with bodies, and of the customs of men. These belong to different philosophical sciences. Hence sacred doctrine is not a single science.
On the other hand: sacred Scripture speaks of these things as of a single science, for it is said in Wisdom 10:10: |She hath given him the science of holy things.|
I answer: sacred doctrine is a single science. The unity of a power or habit is indeed to be judged by its object, but by the formal nature of its object, not by the material nature of it. For example, man, ass, and stone agree in possessing the formal nature of |the coloured,| which is the object of sight. Now since sacred doctrine treats of things as divinely revealed, as we said in the previous article, all things which are divinely revealed agree in the one formal nature which is the object of this science. They are therefore comprehended under sacred doctrine as a single science.
On the first point: sacred doctrine is not concerned with God and with creatures equally. It is concerned with God fundamentally, and with creatures in so far as they relate to God as their beginning or end. Thus the unity of the science is not destroyed.
On the second point: there is nothing to prevent lower powers or habits being differentiated in their relation to matters which yet go together for a higher power or habit, because a higher power or habit comprehends its object under a more universal aspect. Thus the object of the common sense is |the sensible,| which includes both the |visible| and the |audible.| Common sense is a single power which comprehends all objects of the five senses. Similarly, sacred doctrine remains a single science while it treats under one aspect, in so far as they are all revealed by God, matters which are dealt with by separate philosophical sciences. Sacred doctrine is thus like an imprint of God's knowledge, which is one and undivided, yet is knowledge of all things.