A Quantum Critique of Aquinas

How Heisenberg Trips Those On Aquinas’ Way to God

Thomas Aquinas was a brilliant 13th century Christian philosopher and theologian who took his philosophical and scientific understanding of the world seriously. In his lifetime he produced a phenomenal instructional manually for theology students at the university he was teaching at called the Summa Theologica. A famous passage from the Summa provides a compelling fivefold way to proving the existence of God by reflecting on foundational philosophical principles along with what can be seen observationally. Through his understanding of physics, Aquinas is able to determine what is physically possible, and reveals how it is necessary to assume God exists.

His reasoning is quite airtight, but it is reliant on his understanding of physics. Aquinas was a medieval thinker who relied on Aristotle’s understanding of physics, and although his five ways can survive a Newtonian revision, they cannot adapt to the modern quantum understanding of physics. This is because Aquinas’ system, along with Aristotle and Newtonian physics, has the background assumption that the world is deterministic. Quantum physics reveals that this assumption is false, and that events not only can happen randomly, but can happen spontaneously. Specifically, the focus will be turned onto quantum fluctuations, since this single phenomena undoes Aquinas’ first three ways, though there are other examples to point to.

The Nature of Change

In his first way, Aquinas observes that things change all the time, but for change to occur there needs to be something that causes that change to happen.

For to move something is nothing else than to bring it from potentiality into actuality, and it is not possible for something to be brought from potentiality into actuality except by something that is already actual…

Aquinas’ logic is based on the idea that everything has some possibilities to how they are in the world, and that these possibilities can only become actual in reality through something that already is actual. As an example, wood has the potential to be on fire, but it will not catch on fire until something that is hot causes it to change from the state of “not on fire” to the state of “being on fire”. We see then in Aquinas’ understanding of the world that things do not spontaneously change on their own. There must be a logically deterministic operation that one can identify from outside the object. Things are the way they are until something comes along to change that.

Unfortunately, this is at odds with a modern understanding of how physical processes work. According to quantum mechanics, things do spontaneously change on their own. A strict determinism cannot hold in the quantum understanding of the world. Quantum fluctuations are an experimentally supported regularly occurring event in which particles are spontaneously created from nothing in an unpredictable and non-deterministic way, and then quickly destroyed by Heisenberg’s uncertainty principle. The overall net effect of this event is that there was no change, but for a temporary moment there is a truly spontaneous actuality from potentiality without a prior causation. Since this happens all the time, they stack and we get observational non-zero effects.

Aquinas’ reasoning cannot be true then, since we see through our modern understanding of physics that it is not logically necessary that something outside the object brings it from potentiality to actuality. Since quantum physics allows for spontaneous non-deterministic change, it interrupts the logical chain that necessitates an unchanging God who is the first to bring change.

Second Way — The Nature of Causality

The assumption that the world operates in a deterministic way is an absolutely necessary basis on which Aquinas’ reasons, as we can obviously see in his understanding of causality.

And it is not found, nor is it possible to find, that anything is the productive cause of itself; because thus it would exist prior to itself, which is impossible. Nor is it possible to go on to infinity in productive causes.

Aquinas argues that objects cannot self-cause themselves to exist, since if something can cause an effect it too must have been caused by something else. If we remove a cause in a chain of cause and effect, it will remove the effect. If two people do not have sex, they will not have a child. It is logically necessarily that the thing that causes an effect comes before it.

This may seem obvious, but the root of the problem here is that Aquinas’ reasoning is dependent on saying that everything that exists has a determinable cause. His chain of logic then insulates against claiming things are self-causing since they would have to pre-exist themselves to do that. However, as we see with quantum fluctuations, we don’t have to assume that the universe is deterministic. Since there can be all sorts of particles that can produce effects that had no prior cause, Aquinas’ reasoning is completely bypassed. The particles aren’t acting backwards in time to create themselves, they just pop into existence randomly. This means that we cannot reason a first cause of a determinable chain of cause and effects, since we could have a chain started by a quantum system.

Third Way — The Nature of Existence

Finally, we can see that for Aquinas spontaneously creation is completely impossible, which serves as the basis of his third way.

If, then, all things are things for which nonexistence is possible, at some time there was nothing in existence. But if this were true, even now there would be nothing, because what does not exist cannot begin to exist except through something that does exist…

Similar to the previous two ways, Aquinas assumes the world operates in a rigid deterministic way where things can only come into existence because they were brought into existence by something that already exists. For instance, you have an existing electric charge in the atmosphere which creates a lightning bolt. That lightning bolt comes into existence because of charges that already exist.

The spontaneous and unpredictable nature of quantum fluctuations, however, completely ruins this logical chain. The universe does in fact contain things which come into existence without the need of things that already exist. You truly do have something coming to existence from nothing, which just flat out rejects his argument that we need to have an eternally existing God.

One argument that could be raised is that there is something that pre-exists to allow for these particles— spacetime itself which originates in the Big Bang. However, this is a misunderstanding of what the Big Bang is, since it is itself a product of quantum fluctuations.

The Metaphysical World

Aquinas’ fourth and fifth ways do not depending on his physical understanding of the world, but instead his metaphysical understanding, and hence can exist in a quantum world. However, they are both significantly called into question. Can we really argue for the existence of objectively real transcendental properties and a metaphysical ordering of how the world operates? It seems to me that these are completely superfluous in a post-Ockham world. Consider arguably the most likely real transcendental of being. Do we really need a source which causes and sustains existence in some metaphysical way if quantum mechanics tells us that the universe at base spontaneously creates? Do we need to suppose that there truly is a real end to which objects are operating towards implanted by God when we can just say they are mindlessly operating according to the principle of least action? I suppose at some level this is a matter of taste, but it seems unnecessary to say there are such metaphysical properties. It might feel like there must be some objective morality or beauty or truth in a metaphysical way, but there really is no way to talk about an objective scale of these things which can be assigned.

Conclusion

Aquinas was genuinely a brilliant thinker, and he was right for the time he lived in. However, our understanding of the world has advanced unpredictably far in the 800ish years since he was around. It is impossible to understate how revolutionary even the past 120 years of science has been with the discovery of quantum mechanics. This does not even speak to the curiosity of dark energy and modern cosmology, but that is a field that requires more definite research before we can reflect on it philosophically. What we do know is that the universe is strangely constantly spontaneously creating something from nothing all the time. If we use Aquinas’ five ways as a path to God, quantum mechanics shows us that we do not need to posit the existence of God at all. Rather than having a single undivided divine reality that serves as the source of all things, we can have a multitude of completely physical effects that end up producing everything else.

This is a really fascinating opportunity to revise our understanding of theology. Losing Aquinas’ five ways seriously destabilizes any philosophical argument for God. Since you cannot reasonably argue for the existence of God., the whole project of natural theology is ruined. Instead, one must completely rest their understanding of God on whether they are willing to accept divine revelation as valid. Personally, as a (post?ish?-)Barthian, my understanding of God is fully dependent on the self-revelation of the unknowable God in the incarnation of Jesus Christ.