(continued) St Thomas continues:
Having laid down these principles we must observe that commentators have given to the opening chapter of Genesis various explanations, none of which is contrary to revealed truth: and as far as concerns the question in point they may be divided into two groups in respect of their twofold interpretation of the formless state of matter indicated at the beginning of Genesis by the words, The earth was void and empty. (RSV-CE: The earth was without form and void.) Some understood these words to mean that matter was formless in the sense that it actually had no form but that all forms were in it potentially. Now matter of this kind cannot exist in nature unless it receive formation from some form: since whatever exists in nature exists actually, and actual existence comes to a thing from its form which is its act, so that nature does not contain a thing without a form. Moreover, since nothing can be included in a genus that is not contained specifically in some division of the genus, matter cannot be a being unless it be determined to some specific mode of being, and this cannot be without a form. Consequently if formless matter be understood in this sense it could not possibly precede its formation in point of duration, but only by priority of nature, inasmuch as that from which something is made naturally precedes that which is made from it, even as night was created first. This was the view taken by Augustine. Others took the view that the formless state of matter does not denote absence of all form in matter, but the absence of natural finish and comeliness: in which sense it is quite possible that matter was in a formless state before it was formed. This would seem in keeping with the wise ordering of its Maker who in producing things out of nothing did not at once bring them from nothingness to the ultimate perfection of their nature, but at first gave them a kind of imperfect being, and afterwards perfected them: thus showing not only that they received their being from God so as to refute those who assert that matter is uncreated; but also that they derive their perfection from him, so as to refute those who ascribe the formation of this lower world to other causes. Such was the view of Basil the Great, Gregory and others who followed them. Since, however, neither opinion is in conflict with revealed truth, and since both are compatible with the context, while admitting that either may be held, we must now deal with the arguments advanced on both sides.