Metaphysics, Philosophy, Philosophy of Science

Between Possibility and Reality: Heisenberg’s Appeal to Aristotelian Metaphysics, Part Two

by Dave Seng

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.

Metaphysics, Philosophy

Between Possibility and Reality: Heisenberg’s Appeal to Aristotelian Metaphysics, Part One

by Dave Seng

“As there is a material object behind every sensation, so there is a metaphysical reality behind everything that human experience shows to be real.” – Max Planck, Scientific Autobiography

[Note: I would like to thank Dr. Derek Gardner for reading a draft of this essay and supplying helpful suggestions. His scholarship saved me from making errors when describing quantum mechanics and I deeply appreciate his insight.]

I recently heard a professional philosopher say that metaphysics is no longer a dirty word in the field of philosophy. This was good news to me, because for the last four hundred years or so metaphysics has been considered a lost cause in philosophy. Upon reflection, however, I think there has been a small resurgence in the interest of classical metaphysics but the philosophy of mind, language, science, politics, and ethics still seem to be the most popular areas of study in the field. I’m still told that professional positions for metaphysicians are hard to find. Nonetheless, it is fascinating that philosophy is rediscovering its primary role—to explicate the most universal principles of reality and discover the rules, axioms, and laws that make our universe, fields of learning, and human experience possible in the first place. I think the ultimate questions of reality and what it means to be human will never really go away. Thoughtful individuals will always try to offer systematic attempts to illumine our human experience in depth and set it in a vision of the whole of reality. Why might there be an emerging interest in metaphysics and what would that tell us about the relationship between philosophy and science?

Aristotle explains in his Metaphysics that there is a science (for Aristotle ‘science’ is a body of knowledge) which is concerned with “being as being” and that the primary causes and principles of being are the object of study for the metaphysician. This is the formal study of ontology, the metaphysical exploration of all existing things as they exist, the properties of being, and whether certain things, whose existence can be questioned, do or do not exist. Aristotle also laid out the tactical possibilities for conducting what we now call the physical sciences – the study of the structure and behavior of the natural world through repeated observation and experiment. For Aristotle, however, and the many classical and medieval philosophers that came after him, the physical world and the ultimate principles of reality (what they would have called ‘physic’ and ‘metaphysic’) are not to be divorced or separated because both are needed to explain the ultimate nature and significance of reality. While the subdivision and classification of learning and science is helpful for sharpening one’s focus on their object of study, most areas of study ultimately fall back on basic first principles that attempt to explain or support their overall project, such as the principle of sufficient reason, the law of identity, the law of noncontradiction, correspondence, cause and effect, act and potency among others. Perhaps one reason metaphysics is being re-discovered is that all fields of inquiry, whether the social sciences or physical sciences, use foundational first principles which reflect their basic assumptions about the nature of the universe and how the world works. Note that nearly all our basic assumptions are not empirical in the sense used by Enlightenment philosophers and natural scientists and yet it would be foolish to discard them. There are many immaterial and material aspects of reality. The union of the immaterial with the material has often been discarded or forgotten in Western thought but recently have been rediscovered with interesting metaphysical corollaries. Every cosmology, mathematical formula, scientific hypothesis, and ethical theory has metaphysical implications.

Another reason I think metaphysics is being rediscovered is that a few physicists and mathematicians in the twentieth-century ventured into the discussion and pointed out that physics and metaphysics are indeed related and ought not to be detached. This was a profound change in Western thought at least since the Enlightenment. Due to the skeptical theories of Descartes, Hume, Hobbes, and Kant, metaphysics was considered dead or impossible to pursue. However, interesting scientific developments in the early part of the twentieth-century changed things. Einstein’s colleagues, Max Planck, Werner Heisenberg, G.H. Hardy, Niels Bohr, and Erwin Schrödinger, among others, argued for a new understanding of nature due to the quantum discoveries of their day that described the behavior of reality at the atomic scale, where standard Newtonian physics failed to do so. Here, a basic tenet of quantum mechanics, as opposed to classical mechanics, is that reality, at an atomic level is not causally linear or smooth in its behavior but probabilistically discontinuous and discrete. In Newtonian physics, for instance, and in the classical “every day” large-scale sense to which it applies, it is generally possible to determine the future states of a system by knowing its present state (e.g., we can predict where a baseball will land given some initial conditions). In the new atomic physics of the twentieth century, this was no longer the case. Classical mechanics has at its basis the contention that all states of a considered system can be measured and known. When we describe atomic physics with quantum mechanics, on the contrary, one must accept that it is impossible to know the exact value of a parameter without measuring it, and one can know it only for that measurement. Heisenberg’s discovery of quantum indeterminism suggests that in the moment of an atomic measurement, the system (e.g., a molecule) is necessarily disturbed (e.g., by a probing photon) thus “collapsing” the original potential possibility-space into one state of the many probable states, some with much higher probability, but otherwise without any reason to “collapse” into one or another particular possible state (Silva, 637). The most one can do to describe the state of any given system, before or after the measurement, is to provide a probability for the outcome of that measurement (Dirac, 73).

From the standpoint of Aristotelian philosophy, Werner Heisenberg is especially interesting due to his specific appeal to Aristotelian categories of act and potency when describing his theory of indeterminism. Before getting further into Heisenberg’s interpretation of quantum mechanics, however, it is important to understand the central Aristotelian categories of Act and Potential.

As a quick review, ‘act’ or ‘actuality’ simply refers to that which exists. It is the physical, concrete existence of something (philosophers call this the ‘positive mode of perfection’ but we will not go into that here). For now, think of act or actuality as that which really exists here and now—a physical object. Another way to think of act is that which is ‘informed matter’. (In classical philosophy, matter is not form and form is not matter. Form is the essence of a thing or that which makes something the kind of thing it is and without which it can not be. Ordinarily, essence is considered distinct from existence. This is one reason why all reality has an immaterial as well as material elements.) ‘Potential’ or ‘potency’ is simply all the capacities for change, transformation, or movement that which is in act has. For example, a student has the capacity to become a great mathematician if she uses her rational capacities well. A rubber ball has the capacity or ability to be melted down and formed into a figurine, balloon, or tire. Potential is another way of describing all the possible modes of being something has (it is always innate to that which is in act). Potency is never unlimited, however, and is governed by the essence, nature, or form a thing has—and this will be important when we get to Heisenberg’s understanding of probability and atomic potency. For example, a hamster will never become a helicopter pilot, and a cephalopod will never become an architect because potency only relates to the nature (or essence) of the thing itself. Act and potency are metaphysical co-principles that help us make sense of the world around us. The act/potency distinction is an absolute feature of reality and is accepted by all serious philosophers from the classical tradition through the early modern period, including neo-Platonists and Aristotelians. For example, the neo-Platonist philosopher, Plotinus, appropriated Aristotle’s categories of act and potency when describing change.

Part two will specifically focus on Werner Heisenberg’s book, Physics and Philosophy with some concluding remarks from Max Planck.

Works Cited:

Dirac, Paul. The Principles of Quantum Mechanics. Oxford, Clarendon Press, 1958.

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