In my book Particles of Faith: A Catholic Guide to Navigating Science, I use the term system of wills to explain how the physical realm of science fits into the total reality. Thinking in these terms can help you sort out for yourself, and explain to others, any kind of “faith and science” question, be it evolution, free will and determinism, cosmology, or the dignity of human life.
The supreme law
St. Thomas Aquinas teaches in the Summa Theologiæ that there is an order in nature of causes and effects (I.105.6). God created everything and holds all things visible and invisible in existence. God is the first cause, the Creator, not subject to secondary causes such as change and motion in matter. Thomas cites St. Augustine and calls God’s law the supreme law.
Everything created, in entirety, is subject to the supreme law. Matter and energy follow the laws of physics created by God. He even holds all atoms and subatomic particles in existence as they move around according to the prescribed laws that govern them. Since the intellect can move the will, and the will can move matter, beings (angels, humans, and animals) are movers in the physical realm (I.82.3-4).
The laws of physics
Let’s stop here and do a thought experiment. If there were no other created being with any kind of intellect and will, then the material realm (down to the last particle) would follow the laws of physics as God designed and determined them. Think of a lifeless planet like Mars. A preceding motion causes every subsequent motion. The only will that could alter the particles following laws of physics would be God’s will.
Would this be a miracle? Technically, no. St. Thomas calls a miracle something God does outside the order of nature “that we know” (I.105.7) Miracles appeal to our admiration for a manifest effect whose cause is hidden from us. Without humans in the system of wills, there are no miracles.
Do miracles break the laws of physics? Again, no. If God wills to move particles, nothing has happened outside the supreme law. Thomas makes a distinction between breaking the law and exceeding the law: “Therefore since the order of nature is given to things by God, if he does anything outside this order, it is not against nature” (I.105.6). In addition, if God wills to move particles, this cannot be modeled or predicted with human calculation, which is why physics cannot study miracles. Miracles have never been ordered events.
Before any created being is inserted into our system of wills, a point needs to be made. This hypothetical realm is where science works. A chemist or a physicist conducts experiments and performs calculations by defining an isolated system to the best of his ability, removing every other factor, controlling the variables, and examining the effects of changing variables. Remember this when you consider the theories of scientists. They speak of isolated physical systems.
Enter rational beings
The rational beings with free will and intellect are the angels (bodiless souls) and humans (body and soul). Just as God can will to move particles beyond the laws of physics, so too can rational beings—but only in limited ways that God designed. Humans can kick rocks, overcome grumpiness, and build iPhones, but we cannot change granite to gold, make children ungrow, or turn water into wine instantaneously.
Angels are purely intellectual beings or heavenly minds (I.58.3). For them, intellect is perfect at once “from their very nature” in that they instantly know all they are created to know. As free agents, angels can intervene in an otherwise strictly physical reality, too. Since the angels who chose goodness apprehend only goodness, they always will what is good (I.59.2). Indeed, a scientist would do well to remember his guardian angel.
Humans, who have a lower intellect than the angels, must conduct scientific research in order to learn about nature. Aquinas explains that humans pursue perfection in knowledge of truth by “discursive intellectual operation” (I.59.2). Humans advance from one thing to another rationally using sensory data and abstraction, wherein we observe, hypothesize, experiment, and form conclusions and new questions. “Discursive” implies progressing in a slow or irregular manner, sometimes over a wide range of topics. For angels, there is no discursive process.
Nature is a medium
To tie this together, I borrow a concept from C.S. Lewis, who in his 1947 book Miracles refers to nature as a “hostess.” I also like his use of the word incommoded. Of the intervention in physical nature he says, “We see every day that physical nature is not in the least incommoded by the daily inrush of events from biological nature or from psychological nature.” If a cup of tea is invaded with sugar, for example, physical laws rush to accommodate the newcomer. If tea is stirred, physical laws follow suit.
In perhaps a less-poetic manner, I prefer to think of nature as a medium rather than a pleasantly smiling female setting the table. Matter and energy form the physical medium in which we live, a medium that accommodates our actions.
When a violinist pulls her bow across the strings, she intervenes and nature accommodates; music is made. If you throw a ball off the roof, it falls to the ground and, unless another person intercepts it, the projectile motion is calculable. If a woman becomes pregnant, the physical medium surrounding the child accommodates its conception, and the parents have altered the course of a great many atoms for all time.
Human activity causes matter to change, extensively, beyond what matter left to its own devices would accomplish (which is why there are no cathedrals on Mars). Through it all, we do not change the laws. Nature accommodates us. We are higher in the order of causes and effects than the horsehair and wood that constitutes violin bows.
The interlocking totality
Thus, the supreme law and laws of physics are interlocked. Together matter, living things, humans, and angels form the whole systematic universe. Even if scientists were to discover a Theory of Everything that spans the whole of time and space, what they would leave out, as Lewis eloquently puts it, “is precisely the whole real universe—the incessant torrent of actual events which makes up true history.”
Lewis goes on to say that a “miracle is emphatically not an event without cause or without results” either. Christianity obliges us to acknowledge that God can intervene in the world for the sake of our salvation by causing miracles. We see the interlocking totality at every Mass. The bread and wine become the Body and Blood of Christ, miraculously. We receive it into our bodies, and our digestive system does its thing.
The clarification also invites interesting questions. For example, have we ever mistaken events for miracles when, in fact, we simply did not yet have a scientific explanation? Possibly, but God knows the extent of human understanding at any time.
Do angels sometimes move matter, but we mistake the event for a miracle? That is certainly a possibility.
Might there be a hierarchy of intellect and will among animals so they too move matter in indeterministic ways? Walking my German shepherd convinces me at least to entertain the idea.