Interpreting Genesis 1 with St. Thomas Aquinas
In this essay, we will review St. Thomas Aquinas’ interpretation of the account of creation that appears in the first chapter of the Book of Genesis. Like Augustine, Thomas was one of the most influential theologians in the Church, and with the advantage of his predecessors’ excellent work, he was able to produce a coherent theological synthesis that stands even today as the authority of first recourse for difficult theological questions.
We will see here that Thomas has carefully studied older opinions about Genesis 1, but does not choose one over another. Instead he shows where they agree and they disagree, what must be ruled out, and why we can accept differences of opinion where we in fact can. In his own reading of Genesis 1, Aquinas distinguishes three phases within the six days of creation, but he does not discuss whether the days are twenty-four hour periods or are rather symbols of different orders of creatures.
Like the Fathers of the Church, Thomas observes the important metaphysical distinction between creation and change. Creation is the act of making things exist where before nothing existed. In contrast, forming a new interesting thing out of preexisting basic elements is an impressive change, but it is not creation properly speaking. Coincidentally for evolution, the word Thomas uses for “change” is mutatio: He repeatedly reminds his readers that creatio non est mutatio—that is, creation is not change, alteration, development, or mutation.1
Aquinas clarifies that the act of creation requires omnipotence, so there are no intermediate actors in creation.2 Also, as Thomas points out, the act of creation itself is indivisible, i.e. it does not take any time. God instantaneously and effortlessly wills the universe to exist—and so it did and does.3
Regarding the interpretation of the first chapter of Genesis, Aquinas manifests a detailed knowledge of the Fathers’ diverse opinions (e.g. whether the firmament is the heavens, whether the empyrean heaven is the starry heavens; how water, land, air, and vapors develop, etc.4 ), and he appreciates the insights of them all. In his earliest theological synthesis, the Commentary on the Sentences of Peter Lombard, Thomas notes that the view that the world developed over six ordinary days “is the more common position and seems more consonant with the letter [of the text] on a superficial level.”5 But he judges that St. Augustine’s understanding of the six days as signifying different orders of creatures but not different periods in time “is more rational and better defends sacred Scripture against the mockery of unbelievers.” Aquinas says that he “likes this [latter] opinion more” but that “nevertheless all of the arguments can be answered in holding either opinion.”6
In his Summa theologiae, a later work that represents his last word on the matter, when Thomas entertains the question whether the firmament was made on the second day, he begins by repeating St. Augustine’s teaching that two things are important regarding the interpretation of such passages in Scripture:
First, that the truth of Scripture be held without wavering. Second, that since sacred Scripture can be explained in many ways, one should adhere to no explanation so precipitously that he would [still] presume to assert this understanding of Scripture [even if] it were [later] agreed, because of a certain argument, that this position is wrong—lest Scripture be mocked by unbelievers because of this, and the way of believing be blocked for them.7
After reviewing various positions that take “day” as a twenty-four hour period, Aquinas then observes:
But if by these “days” the succession of time is not indicated but only an order of nature, as Augustine would have it, [still] nothing would prohibit our saying in agreement with any of these opinions [above] that the formation of the substance of the firmament pertains to “the second day.”8
So, Thomas advises us not to over commit ourselves to non-necessary opinions that might later be definitively refuted, and he looks for common ground within opposed acceptable views.
Along the same lines, later in this same section on the work of the six days, Aquinas devotes an article to Augustine’s claim that the six days are really one “day,” or event. Conceding that Augustine’s opinion is quite different from that of others on four points, Aquinas draws out the consistency between these contrasting approaches by showing how the divergent conclusions flow from different premises while the understanding of the manner of creatures’ production is not so different. And whose side does Aquinas take? In the last sentence of his argument Aquinas declares that “in order to judge this from an unbiased position, we must reply to the arguments of both sides.”9
As we would expect, Thomas does not think that all theological opinions are acceptable, or that it is simply a matter of personal preference. Returning to his Commentary on the Sentences, we find his sharp distinction concerning how conflicting interpretations of Scripture should be treated:
Those things that pertain to the faith are distinguished in two ways. For certain things are of themselves the substance of the faith, such as that God is three and one, and this kind of thing, in which no one is permitted to opine otherwise. . . . But other things are only accidentally the substance of the faith, insofar namely as they are handed on in Scripture . . . such as many historical facts which can, without danger, be unknown by those who are not obligated to know. And on this kind of facts even the Fathers held diverse opinions, explaining sacred Scripture diversely. Thus concerning the beginning of the world, there is something that pertains to the substance of the faith, namely, that the created world had a beginning, and all the Fathers agree on this. But how it began and in what order it was made pertain to the faith only accidentally, insofar as these opinions are handed on in Scripture, whose truth the Fathers, holding diverse opinions, handed on by diverse explanations.10
Aquinas freely uses the language of Genesis, such as that the sun was created on the fourth day, but he leaves the term in its original poetic ambiguity. In his entire corpus, nowhere does he use the expression “twenty-four hour(s),” and as we have seen, he does not take a position on the question, because neither conclusion can be proven, and the point is not theologically decisive.
Even so, Thomas does comment on the Genesis 1 account. In his prologue to q. 65 in the first part of his Summa theologiae, where he begins his treatment of the six days of creation, Thomas distinguishes three phases:  the work of creation, as given in the words, “In the beginning God created heaven and earth”;  the work of distinction as given in the words, “He divided the light from the darkness, and the waters that are above the firmament from the waters that are under the firmament”; and  the work of adornment, expressed thus, “Let there be lights in the firmament.”
A few questions later in the Summa theologiae, we find a succinct summary of Thomas’ overall position on this issue, i.e. that the idea of creation over a period of time must be ruled out, that it is acceptable but not necessary to hold that there was special development over six days after creation, and consequently, that it makes sense to speak of phases of creation, distinction, and adornment:
According to Augustine, the work of creation pertains to the production of unformed matter and of unformed spiritual nature, both of which are outside of time, as he says in book 12 of the Confessions. Therefore, the creation of either is placed before any “day.” But according to some Fathers, it can be said that the work of distinction and adornment is applied according to some change in creatures, which is measured by time. But the work of creation consists in the divine action alone in the instant of producing the substance of things. And therefore, any work of distinction and adornment is said to be done “in a day,” but creation is said to be done “in the beginning,” which bespeaks something indivisible.11
Although Aquinas does not take St. Augustine’s view to the exclusion of others on the question of what a “day” in Genesis 1 means, his understanding of the act of creation unfolding in two later phases of differentiation and perfection follows Augustine’s lead. At times quoting Augustine explicitly, Aquinas speaks of seminal essences or principles given in creation that blossom into full form later. Obviously he is not thinking of Darwinian evolution, but his thought is not incompatible with what modern science appears to confirm. Here are a few passages to this effect:
God is said to have stopped creating new creatures on the seventh day because nothing was made afterwards that did not come first in some likeness according to genus or species, at least in a seminal principle…. Therefore, I say that the future renewal of the world indeed came first in the works of the six days in a remote likeness.12
For thus we see that all things that were produced in the process of time through the work of divine providence, with creation operating under God, were produced in the first condition of things according to certain seminal patterns, as Augustine says in his Commentary on the Book of Genesis, such as trees, animals, and other things of this kind.13
On the day on which God created heaven and earth, he also created every plant of the field, not actually, but before it should spring up upon the earth, that is, potentially. It was not because of any lack in God’s power, as if he needed time to work, that all things were not simultaneously [created and] distinct and adorned, but so that the order would be preserved in the arrangement of things.14
Ultimately then, Thomas cautions against over committing ourselves to non-necessary and potentially vulnerable theological positions concerning the interpretation of Genesis 1. And he works to show the important harmony among different views held by various Fathers of the Church.
— Rev. John Baptist Ku, O.P.
II Sent., d. 1, q. 1, a. 2, ad 2; SCG II, ch. 17, 18, 20; ST I.45.2.ad 2; ST I.46.2.ad 1; DP, q. 3, a. 2, s.c. ↩
I Sent., d. 21, q. un., a. 1, qla. 1; I Sent., d. 43, q. 1, a. 2, s.c. 1; II Sent., d. 1, q. 1, a. 4; ST I.65.3, ST III.13.2. ↩
I Sent., d. 8, q. 3, a. 2, corp.; I Sent., d. 43, q. 1, a. 2, s.c. 1; II Sent., d. 15, q. 3, a. 3, obj. & ad 4; ST 1.74.1.ad 1; DP, q. 5, a. 1, s.c. 2. ↩
For example, see his De Potentia, q. 4, a. 1, ad 15. ↩
II Sent., d. 12, q. un., a. 2, corp. ↩
II Sent., d. 12, q. un., a. 2, corp. ↩
ST I.68.1. ↩
ST I.74.2. ↩
II Sent., d. 12, q. un., a. 2, corp. ↩
ST I.74.1, ad 1. ↩
IV Sent., d. 48, q. 2, a. 1, ad 3. ↩
ST I.62.3. ↩
ST I.74.2, ad 1. ↩