St. Thomas Aquinas and the Fittingness of Evolutionary Creation


As a priest-scientist who supervises an NIH-funded research laboratory investigating the molecular regulation of cell death, I get a lot of science and religion questions from believers and non-believers alike. The second most common question I get – after the most common truth question, “Do you believe in evolution?” – is the purpose question: “Why did God choose to create via an evolutionary process rather than via special creation?”

Many answers to this purpose question are possible, of course, but I have found that the most illuminating, and often the most surprising, response that I can give is an argument based on the thought of the great medieval and scholastic thinker, St. Thomas Aquinas, who lived in the 13th century. It is a theological argument for the fittingness of evolutionary creation.

St. Thomas was a Christian theologian whose most mature work, called the Summa Theologiae, remains a masterpiece of faith-seeking understanding. In his writings, he frequently used theological arguments for fittingness to reveal the meaning, beauty, and wisdom of God’s actions in the world. Arguing from fittingness involves understanding why an end is attained better and more conveniently with the choice of one particular means rather than another. In this sense, and as St. Thomas himself explains, choosing to ride a horse is more fitting than walking if one seeks to quickly reach one’s destination on a journey (cf. Summa Theologiae, III.1.2). Theologically, arguments from fittingness try to explain how God’s choice of a particular means allowed him to most appropriately attain the end of his actions.

It is important to acknowledge at the outset that theological arguments from fittingness are not demonstrative. In other words, they cannot prove that a certain conclusion necessarily has to be the way that it is. They cannot prove that the conclusion is true. It may be fitting for someone to ride a horse to reach his destination, but he may in fact have chosen to walk instead. Theological arguments from fittingness do not prove doctrine. They attempt to reveal the inner coherence and the wisdom of the divine design, the theo-drama that has been revealed by a God who is true, good, and beautiful. Nonetheless, these arguments have been deployed by Christian theologians throughout the history of the Church to illustrate the coherence, the intelligibility, and the beauty of the Christian faith. For example, the author of the Letter to the Hebrews argues that it was “fitting [επρεπεν] that God, for whom and through whom all things exist, in bringing many children to glory, should make the pioneer of their salvation perfect through suffering” (Heb 2:10; NRSV).

Returning to our topic, we can reword the question as follows: Why is it fitting for God to have created via an evolutionary process rather than via special creation?

To answer this question, recall that for St. Thomas, theological arguments from fittingness attempt to explain how God’s choice of a particular means allowed him to most appropriately attain the end of his actions. Therefore, to grasp my argument for the fittingness of God’s creating via evolution, we need to begin by identifying the end of creation. Why did God create?

The Catholic theological tradition, which is representative of most of the other Christian traditions, has a clear answer to the purpose-of-creation question: God chose to create because he wanted to manifest and to communicate his glory. The Catechism of the Catholic Church, the definitive summary of Catholic doctrine, proclaims that, “Scripture and Tradition never cease to teach and celebrate this fundamental truth: ‘The world was made for the glory of God’”  (no. 293).

How does God communicate his glory to his creatures? According to St. Thomas, God communicates his glory to his creatures by inviting them to participate in his existence. Creatures exist because God, whose essence is existence itself, gives them a share in his existence. This is the fundamental metaphysical distinction that distinguishes the Creator from his creatures: he has existence by nature, while they have existence by participation.

However, St. Thomas also explains that God shares his perfections with his creatures by inviting them to participate in his causality, which in the world manifests itself in his governance of his creation:

But since things which are governed should be brought to perfection by government, this government will be so much the better in the degree the things governed are brought to perfection. Now it is a greater perfection for a thing to be good in itself and also the cause of goodness in others, than only to be good in itself. Therefore God so governs things that He makes some of them to be causes of others in government; as a master, who not only imparts knowledge to his pupils, but gives also the faculty of teaching others. (Summa theologiae, I.103.6)

To put it another way, according to St. Thomas, it is a greater perfection, and therefore, more fitting, for God to share his causality with his creatures, making them authentic causes that can cause by their own natures, than for God to remain the sole cause acting within creation.

As I have explained to my students at Providence College, it is easy for human beings to write a book, but it is impossible for them to make a book that writes itself. On the other hand, God not only causes, but also creates creatures who are in themselves true causes. As such, when God does create creatures who themselves can cause, he manifests his power in a singular manner that signals his omnipotence.

Building upon this Thomistic theological account, I propose that it was fitting for God to have created via evolution rather than via special creation because in doing so, he was able to give his creation – the material universe and the individual creatures within it – a share in his causality to create. In this way, he more fully communicates his perfection to his creation, thus, more clearly manifesting his glory. As St. Thomas points out: “If God governed alone, things would be deprived of the perfection of causality. Wherefore all that is effected by many would not be accomplished by one.” (Summa theologiae, I.103.6)

Note that this is not the causality that allows one to create from nothing, because this causality is the sole prerogative of God who alone is creator. Rather, it is the causality that allows one to create novelty and diversity from pre-existing matter. This is also not the causality that philosophers call primary causality. Again, this is the sole prerogative of God who is able to act solely on his own power. Instead, it is the causality called instrumental causality where God, the primary cause, activates the instrumental causality of his creatures so that he and they can act together wholly and fully, to create, in the same way that an author and his pen work together wholly and fully to write a letter. This is the kind of causality that underlies biological evolution.

In my view, at least three further points follow from this theological argument for the fittingness of evolutionary creation. First, I propose that once God had chosen to create through his creatures, it was fitting that he used evolution to create rather than another means, because evolution is the most efficient way for divine providence to use non-personal instrumental causes to generate novel and adaptive life forms on a dynamic and ever-changing planet.

Take the Chicxulub asteroid strike that impacted what is now the Yucatan Peninsula in Mexico approximately 66 million years ago. There is significant evidence that suggests that this asteroid strike, which left a 110-mile wide crater now buried nearly a mile underground, triggered the mass extinction at the Cretaceous-Paleogene boundary that killed off the dinosaurs. This mass extinction emptied ecological niches throughout the planet that could now be filled with novel plant and animal life.In my view, evolution was the most efficient and fruitful way for God to use non-personal instrumental causes to create novel life forms after this planetary-wide extinction event, because a Darwinian evolutionary mechanism can shape and transform pre-existing life forms so that their surviving progeny can diversify and adapt to the increased number of available ecological niches. Once he had chosen to use non-personal instrumental causality to better manifest his glory, how else could God have used the non-personal instrumental causality of matter to create the novel kinds of mammals and birds that emerged to become the dominant land and marine vertebrates after the Chicxulub asteroid strike wiped out the dinosaurs?

Next, because of the fittingness of evolutionary creation, I also maintain that God did not “waste” life when he chose to create via an evolutionary process. This is a charge often levied against theistic evolution by creationists. For example, Henry Morris of the Institute for Creation Research argues in Exploring the Evidence for Creation that evolution cannot be reconciled with Christianity because, “the standard concept of evolution involves the development of innumerable misfits and extinctions, useless and even harmful organisms. If this is God’s ‘method of creation,’ it is strange that He would use such cruel, haphazard, inefficient, wasteful processes.”

In response, no one thinks that Michelangelo “wasted” marble because there were leftover marble pieces after he had completed sculpting his masterpiece, David. There is no waste when the agent fittingly attains his end. Likewise, I propose that extinct species are not pointless waste. Rather, they were the necessary “leftovers” from the creative evolutionary process that God used to generate the novel and diverse forms of life visible today in a manner most fitting to reveal his glory.

Finally, according to St. Thomas, God created the diversity of creatures because no single creature can adequately reflect the perfection of God:

We must say that the distinction and multitude of things come from the intention of the first agent, who is God. For He brought things into being in order that His goodness might be communicated to creatures, and be represented by them; and because His goodness could not be adequately represented by one creature alone, He produced many and diverse creatures, that what was wanting to one in the representation of the divine goodness might be supplied by another. For goodness, which in God is simple and uniform, in creatures is manifold and divided and hence the whole universe together participates in the divine goodness more perfectly, and represents it better than any single creature whatever. (Summa theologiae, I.47.1)

Therefore, in my view, it was also fitting that God created via evolution rather than via special creation because in doing so he was able to create more species to reflect his glory: With evolution, he created four billion species over a three billion year period, which is significantly greater than the mere eight million extant species today. In fact, it would have been ecologically impossible for all four billion species to co-exist on our planet, because there are only a limited number of ecological niches on the planet at a given moment in time.

To put it another way, there is a limit to the number of species and individual organisms that can be sustained by the planet at any one moment in time. Some of them are even mutually exclusive: If they had been created together, the large carnivorous dinosaur, Tyrannosaurus rex, would likely have wiped out the Asian elephant, Elephas maximus. However, with evolutionary creation – and not with special creation – these species were able to exist at separate moments in history to uniquely manifest the glory of their Creator. Again, they were not wasted.

To sum up, why did God choose to create via an evolutionary process rather than via special creation? Because it better reveals his glory and his power. Because it reveals better that he is God.


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Rev. Nicanor Pier Giorgio Austriaco, OP
About the Author

Rev. Nicanor Pier Giorgio Austriaco, OP

Rev. Nicanor Pier Giorgio Austriaco, O.P., currently serves as a Professor of Biology and of Theology at Providence College in Providence, Rhode Island. He received his Ph.D. in Biology from M.I.T. where he was a Howard Hughes Medical Institute (HHMI) fellow in the laboratory of Prof. Leonard Guarente. Fr. Austriaco also completed a Pontifical Doctorate in Sacred Theology (S.T.D.) at the University of Fribourg in Switzerland. His NIH-funded laboratory at Providence College is investigating the genetic regulation of programmed cell death using the yeasts, Saccharomyces cerevisiae and Candida albicans, as model organisms. His first book, Biomedicine and Beatitude: An Introduction to Catholic Bioethics, was published by the Catholic University of America Press.