Explaining Miracles with St. Thomas Aquinas

In his beautiful treatment of the resurrection in the Summa theologiae, Thomas Aquinas writes that one of the reasons why Christ had to rise from the dead is to “confirm our faith in his divinity” (ST IIIa, q. 53, a. 1) Christ’s resurrection—and his prior raising of Lazarus—are miracles that teach us about who Christ is and strengthen our hope for our own future resurrection.

Miracles, however, are viewed with some suspicion these days. There are many rare or astonishing occurrences. Some turn out to be not so miraculous on closer observation. What makes something be a miracle, specifically? We may never have seen a resurrection with our own eyes. But many of us have known, first or second hand, astonishing medical recoveries. In such cases, it is especially hard to know how to apply the concept of miracles correctly.

As we rejoice in the miracle of Christ’s rising from this dead, I want to consider the resources Aquinas offers to help us understand what a genuine miracle is, as opposed to other astonishing events. We will proceed by considering four questions: (1) How do people typically use the word “miracle” today? (2) What does Aquinas think a miracle is? (3) What does he mean by God’s “hidden activity in all things”? (4) What is so special about miracles as opposed to other divine activities? (5) What does Aquinas’s approach to miracles mean for our spiritual life?

What is a Miracle? Popular Views

How is the term “miracle” typically used in ordinary conversation? In one sense, “miracle” is used for something that is amazing, wondrous, unbelievable. This sense comes closest to its Latin root: “miror, mirari,” to wonder, to marvel at, to be astonished, to be amazed. Think of new parents, for instance, admiring their baby and saying, “Look at these miraculous little fingers!” They are describing something amazing.

Another sense of the term “miracle” often appears in medical contexts, as in the following headlines: “Quick thinking leads to miraculous recovery of a stroke patient at VCU Health”; “North Carolina teen makes miraculous recovery after traumatic brain injury.” In these stories, the emphasis is on either the fact that the recovery is unexplained, or the fact that the recovery was either highly unlikely or unusually quick. In this second sense, then, the word “miracle” is being used for something unexplained or mystifying.

This second sense of “miracle” can become rather confusing. Consider this quote: “Dr. Reavey-Cantwell believes Chwanda’s remarkable recovery is part miracle and part perfect execution of emergency stroke protocol. She was probably as close to death as one can really come and then came back and made an incredible recovery.”

“Part miracle, part protocol”? We say such things all the time. Indeed, it seems pious to try to give both God and medicine their due. But what does it mean, exactly? Which part did God cause, and what part did the doctors cause?

This way of thinking gets under the skin of skeptics, who object that “miracle” is just a label we slap on anything mysterious. Skeptics insist that these recoveries are all medicine and human biology; we just do not fully understand how medicine and biology work yet.

It is tempting to respond to skeptics by saying that even if the recovery is completely explained by medicine, that still does not exclude God’s working a miracle through doctors—a common formulation. But that response leads to more trouble: what should we say about other recoveries? Do doctors do those without God? Surely not: God is also acting through the doctors when I recover from pneumonia with antibiotics. But if so, does that not mean that every recovery is miraculous? And then what is the sense of talking about miracles if everything is a miracle?

The sequence repeats itself over and over. We appeal to miracles when something is inexplicable, making God fill the gap. This triggers the skeptical objection that natural causes are sufficient; we just do not understood them fully. Finally we try to rescue miracles by installing God a step behind natural causes, making them successful. But this all results in a rather muddy picture of how God works in the natural world, open to many objections. Clearly, we do not have a good handle on the concept of miracles.

What is a Miracle? Thomas Aquinas’s View

Let us see what Aquinas says about miracles. For Aquinas, the first step toward understanding miracles is to understand why God works miracles. The reason, he says, is to provide “arguments for faith, so that through these deeds which exceed nature, the truth is proved of that which transcends natural reason” (De potentia, q. 6, a. 9).

This formulation is surprising: how is a miracle an argument?

To understand what Aquinas means, imagine the human mind like a ship floating around on the waves of thought. In order to “settle” on, “or assent to” a belief, it needs to put down an “anchor” weighty enough to hold it in that spot. One type of “anchor” might simply be an observation. For instance, if I look out the window or check my weather app, what I see will cause me to assent: “It is sunny outside.” Arguments can also “anchor” my mind to beliefs. For instance, if I want to know if my Italian friend is a citizen of the EU, I could reason: “Well, he is an Italian citizen, and all Italian citizens are citizens of the EU.” The “weight” of that argument makes me assent: “So it is true: he must be a citizen of the EU.” For Aquinas, some truths about God, namely, “God exists,” can be known this way, being anchored through an argument of natural reason.

But what about truths about God that cannot be known by natural reason: for instance, that God is a Trinity, that Jesus rose from the dead, or that the consecrated bread is the Body of Jesus? How do our minds become anchored to the truth of these doctrines of faith?

For Aquinas, one way is through miracles. Miracles are weighty enough to “settle” our minds on the truth of these teachings of the faith. That is why Christ worked miracles during his earthly life, and why God confirmed the preaching of the apostles through miracles, and why Christ rose from the dead as the ultimate miracle confirming the truth of his claims. All of these miracles have the same role with respect to truths of the faith, as arguments of natural reason have with respect to truths known through natural reason. They provide the “weight” that moves our minds to assent.

Here we can see a connection to the first popular sense of “miracle” as something wondrous or amazing. For Aquinas, a miracle is God’s strategy for catching our attention and provoking our wonder—not, however, for the sake of wonder itself, but specifically to move us to believe God’s word. This is important: miracles are not displays of divine power for curiosity-seekers, but are specifically meant to move us from disbelief to belief, or to strengthen a shaky faith. (Consider, for instance, the “Miracle of the Sun,” which Our Lady promised to the children at Fatima as evidence of her speaking the truth.)

Miracles, then, are deeds that God does to provoke our wonder and thereby move us to faith. However, Aquinas cautions us that we often wonder at things that are not miracles. In fact, we wonder in two circumstances: (1) when the cause of the occurrence is hidden to us, and (2) when the occurrence goes against our expectations. So he says: “Someone might wonder at the sight of a fragment of iron lifting up toward a magnet, not knowing that magnets have a natural power to attract iron, and expecting iron to fall downwards.” Here the wonder is only subjective, deriving from the viewer’s ignorance. A scientist, in contrast, would have expected the iron to go upwards (De potentia, q. 6, a. 2). Here we see a connection with our second popular sense of “miracle” as something unexplained or mystifying.

Against this popular sense, though, Aquinas says that genuine miracles do not just subjectively cause wonder, but are objectively wondrous. “Something is wondrous in and of itself (per se),” Aquinas says, “whose cause is essentially hidden, and when the effect that appears is contrary to the natural disposition of the thing” (De potentia, q. 6, a. 2). Here he gives us two criteria that are not dependent on our ignorance of natural causes: miracles are deeds (1) performed by an essentially hidden cause, that are (2) contrary to natural tendencies.

Regarding the first condition, Aquinas explains that God alone is the only truly “essentially hidden” cause. Any creaturely action would be at least in principle something human beings can understand, even if our current scientific understanding falls short. But our created minds are incapable of fathoming divine power. Anything that God does when acting alone must therefore be objectively wondrous.

But what about the second criterion, that a miracle must counter a thing’s natural tendencies? In a case like the Resurrection, we can see how this works: the human body naturally tends toward corruption, and corruption is naturally irreversible. Therefore God, acting alone, reverses this tendency, bringing Jesus back to life. But how can a healing, for instance, be “contrary to the body’s natural tendencies”? Surely the body has a tendency toward being well or healthy. Why should God not work a miracle through the body’s natural tendencies? As an extra complication, Aquinas himself insists that God is always “working most hiddenly in all things.” Why should we not say, then, that everything is a miracle? Why insist that miracles have to be contrary to natural tendencies?

This contrast with natural tendencies is at the heart of Aquinas’s understanding of miracles. So let us take a closer look at how he thinks God “works most hiddenly” in ordinary cases, through natural tendencies—one of Aquinas’s most beautiful philosophical ideas.

The Actions of Nature and the Actions of God

Aquinas insists that creatures, like their creator, have the dignity of being actors or agents in the world. An oak-tree, on this view, is not just an assemblage of matter moved around by forces. An oak-tree has a nature that is dynamic and active, continually bursting forth into oak-actions: absorbing nutrients, unfurling its own leaves, turning toward the light, stretching out its limbs in the direction of a mature oak-shape, bringing forth acorns.

These actions are something the oak tree does for itself. Like a spring under tension, the oak tree is full of energy impelling it toward its characteristic actions, which are expressions of its nature, or self-communications. As the great Jesuit poet Gerard Manley Hopkins puts it: “Each mortal thing does one thing and the same / Deals out that being indoors each one dwells / Selves — goes itself; myself it speaks and spells / Crying Whát I dó is me: for that I came.” The oak tree is full of its own coiled-up energy impelling it into actions in which it silently speaks its own nature. That is what Aquinas means by natures having “tendencies.”

So if creatures perform their own actions, what is there left for God to do? Having created a profoundly good and active world, does he simply sit back and look on, perhaps intervening every so often to tweak something with a miracle?

No. Instead, the more active creatures are, the more active God is in his creatures. The reason is that God alone can cause existence. Oak trees do not have existence from themselves; they are not responsible either for their beginning to exist or even for their continuing to exist. (Otherwise they would eternally and necessarily exist, like God.) Existence is something that has to be continually poured into them to keep them going, because they have no inner resources to cause it themselves.

Think of it this way: “being” or “existing” is like an electrical current running through the whole of creation. Creatures do not make their own electricity; they need a continuous supply. That is exactly what God does: if he stopped bestowing being for even one instance, the universe would revert to nothingness. He is doing it to each of us right now; to the room we are in, to the chairs we are sitting on, to the air we breathe, to each one of us, to the functioning of our internal organs—all of that is being continuously sustained with existence by God.

Aquinas takes this idea a step farther: whenever any creature is acting, besides giving the creature existence, God is also giving existence to the creature’s own action and effects. For instance, when the tree performs the action of producing chlorophyll in a leaf, God gives existence to that action, and acts with the tree to give the chlorophyll existence as well. Every time a creature reproduces, God is acting in and through it to give existence to the baby creature. Moment by moment, creature and creator are collaborating (what philosophers call God’s “concurrence” with creaturely actions). God is constantly breathing the life of existence into each of his creatures’ actions and rendering it fruitful. This does not mean that God performs his own act of causing existence and the tree is performing its own separate act of producing chlorophyll in a leaf. Rather, Aquinas insists that God and creature together perform one single act—the existing act of producing chlorophyll.

Now we can finally understand why Aquinas says that God acts “most hiddenly in all things.” When a tree produces chlorophyll in a leaf, the reason we cannot detect the divine action is not that there are two different actions: one observable action by the tree, and one hidden action by God. Rather, there is just one action. Thus in our ignorance, we conclude that the tree by itself fully explains the action we observe, like fish who cannot grasp the water we swim in. We cannot see that the tree’s action is at the same time God’s action. God’s activity in creatures is utterly pervasive and also utterly undetectable.

What does this mean for medical recoveries? The human body naturally tends toward health, performing a range of actions through different organs, to restore its own equilibrium and well-functioning. It is an agent of health. And the medical arts are ways of supporting the body’s natural tendencies toward restored well-functioning, whether by removing impediments (surgery) or by medications that either suppress ill-functioning parts or stimulate the body’s self-healing activities.

But now we can see a new and important insight: all of these actions—the body’s striving to heal itself and the medical professionals’ actions in support—are just as much actions of God, who gives existence to those actions and their effects. In every recovery, God is “acting most hiddenly,” whether that is a harrowing six-month battle with Ebola, or relief from spring allergies.

What’s So Special About Miracles?

Armed with these ideas, we can return to Aquinas’s second criterion for miracles: namely, that they are contrary to natural tendencies.

We just saw that God collaborates with everything creatures do, but that this divine activity is “most hidden.” In contrast, a miracle is never hidden—it is the opposite of hidden. It is a manifestation of divine power for the sake of faith. So the occurrence must be able to make us recognize its objective wondrousness. Since God’s action in natural causes is undetectable, a miracle needs to break out from the patterns of natural actions. That is how it draws our attention and shows us that God alone is acting from the immensity of his divine power, without the cooperation of natural causes.

Aquinas identifies three ways that a miracle can be contrary to natural tendencies, classifying examples from Scripture (De potentia, q. 6, a. 2, ad 3). First, some miracles work in the opposite direction of a natural tendency (contra naturam). For example, the three boys in the fiery furnace are not burned, even though fire naturally tends to burn. In another example, the waters of the Red Sea hold up their own weight to open a path for the Israelites, even though heavy things naturally tend to fall downwards. And the Virgin Mary conceived, even though human reproduction naturally perpetuates the species through the action of the male (as Aquinas thought in those days).

Second, other miracles operate in a domain where natural tendencies simply cannot reach and never operate, causing effects that no creature could cause (supra naturam). For instance, there is no natural power that can make a body incorruptible—but this is something that God will do to our resurrected bodies. And there is no natural power that can join a human nature to a divine person—but this is something that God does in the Incarnation, which Aquinas calls the “miracle of miracles” (De potentia, q. 6, a. 2, ad 9).

Third, some miracles are the type of thing that a creature has natural tendencies to do, but we know God is the one doing it without the creature’s involvement, because the deed occurs at a speed or quantity impossible for creaturely powers. He calls these “miracles beyond nature” (praeter naturam). For instance, frogs naturally tend to produce more frogs. But Egypt’s plague of frogs was a miracle, because the sudden boom in the frog population far exceeded anything that the natural reproductive powers of a frog could have accomplished.

Interestingly for us, this is where Aquinas places miraculous healings, using the example of Christ healing Peter’s mother-in-law. The body has its own natural tendencies toward recovering health, he explains, but these physical processes take some time to unfold through their predictable series of steps. The reason the mother-in-law’s recovery is miraculous, then, is that it is instantaneous. The instantaneousness shows that her healing is the act of God alone, and not her body’s natural processes.

From these examples, it is clear that for Aquinas, miracles must be recognizable as God acting alone, without natural causes.[1] We can recognize an extraordinary event as God’s action alone, only when creatures cannot bring about such an effect—either because it is contrary to the creature’s natural tendencies, or it occurs at a level where creaturely powers cannot operate, or it would be impossible for a creature to do in the way that God does it.

Thus the popular senses of “miracle” today do get something right: miracles are both amazing and inexplicable—amazing so that they will catch our attention and move us to faith, and inexplicable so that we will be amazed. But for Aquinas, amazement and inexplicability are not enough. As he points out, we can easily confuse “things that nature does” for miracles, simply because “we do not understand the causes” (De potentia, q. 6, a. 2). And demons, magicians, and clever tricksters are able to awe us by manipulating natural causes or causing illusions (De potentia, q. 6, a. 5, and q. 6, a. 10). Thus the only way to know that God alone is acting is when we can recognize that the action is impossible for natural powers and tendencies.

So what conclusions can we draw about God’s involvement in amazing medical recoveries? Our difficulties here come from losing an important philosophical tool, i.e., the classical notion of a natural tendency, which has been replaced by the notion of statistical probabilities. For instance, medical research tells us that Ebola has an 80% case fatality rate—but that “early supportive care” like rehydration, blood transfusion, and the treatment of secondary infections, can “significantly improve” outcomes. So the patient who does get such treatment and survives has certainly beaten terrifying odds. But she also did get treatments that are known to increase the probability of survival. Thus we ask: a miracle or just luck?

Instead, Aquinas would say, we should be asking whether the recovery is consistent with the tendencies and activities of natural powers. If the answer is yes, then the divine activity is hidden in the natural action. And without a manifestation of divine power, there is no miracle. Now recovery from Ebola is evidently something the human body can achieve through its natural powers with certain treatments. No matter how statistically unlikely such a recovery is, it is still the result of natural powers acting. Those, of course, are also God’s actions—but in the standard, “hidden” way, not as a special divine intervention.

But if the recovery is not consistent with the tendencies and activities of natural powers, then the activity is God’s alone, on display for our amazement and salvation. Consequently, a properly miraculous cure, on Aquinas’s view, must “exceed” natural powers: for example, the repair of an irreparably damaged eye, or an impossibly rapid complete healing, as occurs sometimes at Lourdes. And, of course, the Resurrection itself.

Takeaways: What Does Aquinas’s Teaching on Miracles Mean for Us Today?

Aquinas’s teaching on miracles leaves us in an interesting, yet perhaps spiritually challenging, spot. On the picture Aquinas draws, miracles are not everywhere. Miracles are unmistakable, striking, clear deeds of God alone, capable even of causing conversions. When God intervenes with a miracle, it is always for our salvation: to restore what sin destroys through the miracles of the Incarnation and Resurrection, or to move us to faith. In fact, miracles are essentially the expressions of God’s persistent desire to draw us into a life beyond the natural world, the life of grace.

On this view, then, God is not constantly “adjusting” the course of history with small unnoticed interventions. God is perfectly capable of bringing about his ultimate plan for creation simply by acting through creatures exercising their own natural powers. We can trust that whatever happens, whether joyful or tragic, is consistent with God’s providence. But Aquinas gives us no fuel for the idea that the lucky coincidences or statistical improbabilities that we sometimes describe as “small miracles” are actually divine interventions at all.

Initially, this is not a comforting thought. Perhaps the idea of frequent small miracles feels like a reassuring sign of God’s attentive care, showing that God does not “abandon” us to natural forces and human decisions, but cares enough to intervene repeatedly in the plot line.

Worse, Aquinas’s insistence on God’s universal hidden activity sharpens the problem of evil. Sometimes the natural actions in which God operates enable a friend to survive a car crash or recover from a dangerous illness. But the opposite can just as well be true; God equally operates in the natural actions that fail to restore health, the unsuccessful last-ditch treatments after which the patient dies anyway. God even gives existence to creaturely actions that are deformed by moral evils—to acts of will twisted into hatred of God or neighbor, or horrific acts of cruelty visited on another. Why does God cooperate with such evils at all?

This is a very deep problem to which only the mystery of the Cross provides an answer. But let me focus instead on what are two very important spiritual advantages of the contrast Aquinas draws between miracles and God’s universal hidden action.

First, Aquinas’s view protects against the skepticism that constantly threatens someone with a less rigorous view of miracles. If we take statistical improbabilities and coincidences as miracles, a skeptic can too easily come along and destroy the “magic” by showing how natural causes actually do explain the event. Since miracles are motivators for faith, this kind of “debunking” can be devastating. The believer may feel forced into a dilemma: either to abandon the idea of miracles, or to double down on the miraculous nature of the event from raw feeling alone—“I choose to believe it is a miracle.”

Repeatedly being forced into such dilemmas causes spiritual damage, training us to view faith as a purely emotional and anti-rational frame of mind, splitting faith apart from the reasoned study of the natural world. Nothing could be farther from Aquinas’s mind. For him, what faith teaches is never in competition with reason. Aquinas shows us that asserting God’s activity is not incompatible with explanations through natural causes. Rather, reason itself argues that the very fact that natural causes exist and are effective at all relies on the hidden activity of God in and through all things. But we have to be willing to see God’s activity and providence in everything, as it truly is, not picking and choosing.

That takes us to the second advantage of Aquinas’s view: the high bar Aquinas sets for miracles frees us to become fully aware of the pervasiveness of God’s presence in our midst. Whether we know it or not, we thirst for God’s presence with a consuming intensity. We can divert that energy into sifting through tea leaves looking for something to call a divine intervention—but that will never really quench our thirst. Our need is to be completely immersed in God, breathing him in incessantly, not just to have him drop by occasionally to lend a hand. By reserving miracles for dramatic, unmistakable signs of God acting alone without nature, Aquinas encourages us to drink deeply of God’s presence, not just in the events we choose to interpret as signs of his care, but as concurrently active in everything around us.

When we think this way, the sheer breadth of God’s presence in our lives is mind-boggling. We do not have to wait for a miracle to see it. The very predictability of the fruit ripening on a tree, the water flowing downwards out of the tap into the basin, the particles of dampness crystallizing into snow, the wheels of the car rolling forward—each is its own gift, the fruit of God’s concurrent action as he breathes existence into the action of each creature striving to exercise its nature, upholding the fragile and rootless web of creation with a constant influx of being.

Here, Aquinas opens up the possibility of totally reorienting our vision, until we can see everything as a sign of God’s presence. This is no easy task. We are more attuned to God’s mercies when events turn out the way we wanted—the dream job offer, the friend’s recovery, the Hail Mary that actually gets caught. But Aquinas gently draws our attention to God’s thornier presence in and through disappointments, disasters, and tragedies (the fumbles and interceptions). God is active there too, breathing existence into creaturely actions that are painful to us.

What does it mean? When we grapple with the fact that God’s hidden activities pervade all the moments of our life, delightful or painful, we are shaken out of our childish tendency to treat God as the rich uncle of the cosmos, who just might intervene this time to make our dreams come true. We begin to see that God’s ways are infinitely above our own; he gradually teaches us to see beyond the limited horizon of what we think will make us happy, to the infinitely better desire he has for us: to unite us to himself.

Thus Aquinas notes that just as faith takes its “arguments” from God’s actions beyond the capacities of nature, so too does faith invert our expectations about happiness, showing us that “poverty in temporal things earns spiritual riches, and humility earns heavenly nobility” (De potentia, q. 6, a. 9). But even if the learning is painful, God holds us up through it all, intimately and lovingly sustaining each one of us and giving fruit to our actions.

And in case we have a hard time believing that—well, he is the Risen Lord of all nature, after all. So he can always stop nature in its tracks, and help us along with a miracle!

EDITORIAL NOTE: This article was originally delivered as a Saturdays with the Saints lecture, sponsored by the McGrath Institute for Church Life, on November 16, 2024.

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