So what do Aristotelian-Thomist notions of act/potency and form/matter have to do with quantum dynamics? In 1975 Werner Heisenberg gave a lecture to German physicists and said, “good science is being unconsciously discarded because of bad philosophy” and sought to correct the situation with his book, Physics and Philosophy. The bad philosophy that Heisenberg wanted to redress was the materialistic, mechanistic, and deterministic view of nature assumed by Enlightenment physicists and philosophers. He specifically appealed to the metaphysics of Aristotle to correct the deterministic view of Newtonian physics. It is important to note at this point that much of Aristotle’s ideas were either thrown out or misinterpreted by early modern philosophers and scientists due to their materialist assumptions. Heisenberg’s appeal to Aristotle’s metaphysics was a bold new move for his day but he realized it made the most sense out the facts as they were presented to him.

So what was Heisenberg getting at when he explained the function of sub-atomic particles in the Aristotelian category of ‘potential’? In his book Physics and Philosophy, he tells us:

“In throwing dice we do not know the fine details of the motion of our hands which determine the fall of the dice and therefore we say that the probability for throwing a special number is just one in six. The probability wave of Bohr, Kramers, Slater, however, meant more that; it meant a tendency for something. It was a quantitative version of the old concept of “potentia” in Aristotelian philosophy. It introduced something standing in the middle between the idea of an event and the actual event, a strange kind of physical reality just in the middle between possibility and reality” (396).

According to Heisenberg, the probability inherent in quantum behavior is potential – a tendency for something. (This might also imply a ‘telos,’ or purpose, but we will not develop that here.) Heisenberg is clearly stating that the many abilities, capacities, possibilities, or dispositional properties a sub-atomic particle has is its potential.

When explaining the unity of matter as energy or universal matter (similar to Aristotle’s ‘prime matter”) Heisenberg says this, “If we compare this situation with the Aristotelian concepts of matter and form, we can say that the matter of Aristotle, which is mere “potentia,” should be compared to our concept of energy, which gets into “actuality” by means of the form, when the elementary particle is created” (440). Here Heisenberg is intuitively correct. Matter is always in potential. Contrary to early modern philosophers such as Descartes and others, matter and form are not so easily thrown out. Matter and form, or as Heisenberg might say, energy as a form of matter are necessary conceptual tools which physicists use to describe the world. Here, it is important to note two things, the first is that potential is not empirical, the second is that potency is not pure chaos.

First, potential is inaccessible to the strict empiricist. No empiricist who believes that all human knowledge is restricted to what can be observed by some sense experience can allow for potency. Why? Because although potency can be observed through act as an effect (in hindsight, so to speak), it can not be directly observed by itself through sense perception. This is why no real scientist is a strict empiricist because they are always appealing to properties, capacities, probabilities, or capabilities of matter, even though potential is never known by itself apart from that which is in act. The second thing to keep in mind is that at the quantum level, the range of probabilities (potential) is not absolutely indeterminable or chaotic. Heisenberg’s uncertainty principle states that the quantum mechanical behavior of sub-atomic particles is not absolutely indeterminate because it can only oscillate between a range of probabilistic values (Silva 638). This is why things correspond to their nature or essence. Potency can only have an effect on a range of possibilities to that which is in act.

Finally, Heisenberg claimed that many of his fellow physicists were coming to the same Aristotelian conclusions, “One might perhaps call it an objective tendency or possibility, a ‘potentia’ in the sense of Aristotelian philosophy. In fact, I believe that the language actually used by physicists when they speak about atomic events produces in their minds similar notions as the concept ‘potentia.’ So the physicists have gradually become accustomed to considering the electronic orbits, etc., not as reality but rather as a kind of ‘potentia’” (447). Heisenberg came to realize that many of his colleagues were beginning to understand the philosophical implications of quantum dynamics in Aristotelian terms. This should not be surprising since reality is the determinate of order and will always reveal its own intractable way of being.

Max Planck, who is considered the father of quantum theory, also held that scientific discoveries ultimately point to a metaphysical reality. Although he did not explicitly use the category of potential, he was very aware of the philosophical implications of quantum mechanics. “As there is a material object behind every sensation, so there is a metaphysical reality behind everything that human experience shows to be real” (97). Potency seems to be the best metaphysical category that explains the mysterious behavior of quantum particles. It certainly cannot explain the entire mystery, for there are still many remaining questions for science to explore but act and potency are viable options that the physicist and metaphysician can use to describe reality. These metaphysical co-principles have stood the test of time and point us to the nature of ultimate reality. In many ways, reality itself points to a metaphysical reality. Plank went on to explain that, “Metaphysical reality does not stand spatially behind what is given in experience, but lies fully within it. … The essential point is that the world of sensation is not the only world which may conceivably exist, but that there is still another world. To be sure, this other world is not directly accessible to us, but its existence is indicated time and time again” (98). The metaphysical co-principles of act/potency and form/matter help us understand what is happening in the physical realm.

From these remarks by Planck and Heisenberg, and through an investigation of the Aristotelian categories of act and potency, we see that reality by its very nature is oriented toward self-expressive action. In classical philosophy, the physical world is seen as “one and many” or “being and becoming” (both are needed to make sense of the world). Potentiality, however, is the category used for explaining the dynamic aspect of life. Nothing in the human, animal, or plant kingdoms can grow, develop, or meet its potential by being static. To stand out of nothing—the very meaning of existence—is to be oriented toward action and is the reason there is a metaphysical basis for reality, even at the atomic level. The Aristotelian categories of act and potency account for the dynamic and changing realities we experience in the world around us. Potency itself is not a strictly empirical phenomenon but is indispensable for accounting for and maintaining the integrity of the empirical data. There are all sorts of non-empirical realities that nature itself points us to—from the smallest sub-atomic particle to human nature itself.

[Special thanks and gratitude go to my friend Dr. Derek Gardner at the University of Arizona for keeping me pointed in the right direction regarding the issues around quantum physics. Without his guidance my ontology would have certainly failed.]

Works Cited

Heisenberg, Werner. Physics and Philosophy. Great Books of the Western World. Vol. 56. Encyclopedia Britannica, Inc., 1999

Planck, Max. Scientific Autobiography and Other Papers. Great Books of the Western World. Vol. 56. Encyclopedia Britannica, Inc., 1999

Silva, Ignacio. “Werner Heisenberg and Thomas Aquinas on Natural Indeterminism.” New Blackfriars, 2013, 635 – 653.

For further reading:

Clarke, Norris. The One and The Many: A Contemporary Thomistic Metaphysics. University of Notre Dame, 2001.

Goetz, Stewart and Charles Taliaferro. Naturalism. Wm. B. Eerdmans Publishing, 2008.

Trigg, Roger. Beyond Matter: Why Science Needs Metaphysics. Templeton Press, 2015.

Moreland, J.P. Scientism and Secularism: Learning to Respond to a Dangerous Ideology. Crossway, 2018.