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What Is Matter? The Aristotelian Perspective


Writing here yesterday, I pointed out the problems with materialist metaphysics. The problems are profound, and have led to all sort of scientific nonsense, materialist theories of cosmology, biology, evolution, and the mind being prime examples.

The Cartesian (materialist) error was a move away from Aristotelian metaphysics, which (as developed by Thomas Aquinas and other scholastic philosophers) was a much more rigorous and coherent metaphysical system. And the question: “What is matter?” is a cornerstone of Aristotelian metaphysics.

Aristotle was motivated by the question: How do we explain change in nature? Pre-Socratic philosophers had struggled with this question, and the problem of change was in a sense the central dilemma of ancient metaphysics. Change in nature seems to entail contradictions. Change seems to occur, but what is it that undergoes the process of change? If something changes to something else, then it seems that it really isn’t change, but the going out of existence of one thing and the coming into existence of another thing. Parmenides believed that change was impossible, an illusion. Everything stayed the same in nature, and apparent change was illusory. Heraclitus took the opposite view: all of nature was change, and nothing ever persisted. Change was continuous, and stasis was an illusion. It seemed that there were only two possible ways something could come to be (in the sense of change): either from what is, or from what is not. But “from what is” wouldn’t be a change, and “from what is not” is nonsense. Nothing can come from nothing. Aristotle described this argument succinctly: “What is cannot come to be (since it already is), while nothing can come to be from what is not.” (Physics 191a 28-29)

Aristotle, with characteristic perspicuity, gave an answer that transformed the way we understand nature. He first asked: What exists? He answered that substances (Greek ousia) exist. A substance is a specific existing natural thing, like a stone, or a tree, or a man. Aristotle saw that substances were composites, not of other substances, but of principles.

First, there is the principle of intelligibility. The principle of intelligibility is everything that can be known about the substance — the shape, the weight, the structure, etc. This principle is the form of the substance.

Second, there is the principle of individuation. The need for a principle of individuation can be understood from this consideration: I could describe everything that can be known about something, but that description (that form) could apply to any number of individual things. The principle of individuation is the principle in a substance that makes it that individual, and not another. This principle Aristotle called matter. (Specifically, prime matter.)

Every substance is a composite of form (intelligibility) and matter (individuation). The composite ordinarily is not separable — you can’t pull the form out of the matter and put them side-by-side. A substance is a unitary thing. The form and the matter that comprise it are principles, not things in themselves.

Aristotle showed how this hylemorphic (matter-form) perspective explained change. Everything that exists has things it can be (but is not) and a thing that it is. An acorn can be an oak tree if it grows (the “can-be-but-is-not” part) and the same acorn is an actual acorn (the “thing- that-it-is”). Aristotle called the material principle in a substance the potency, and the formal principle the act.

Every substance is in potency and act for various properties. Change occurs when potency is elevated to act — that is, when what something potentially is becomes what it actually is. In this way, Aristotle explained change in nature: change is elevation of potency to act. The matter (which is the subject that persists in change) remains while the form changes. The potency (matter) is what persists through change, while the form changes.

With the onset of the age of quantum mechanics, many scientists and philosophers were astonished and perplexed by the strange quantum world. The reason they were astonished is that they presupposed (generally without realizing it) a Cartesian definition of matter — that is, that matter is tangible stuff extended in space. But that definition of matter is woefully inadequate to explain nature.

Heisenberg, almost alone among the great physicists of the quantum revolution, understood that the Aristotelian concept of potency and act was beautifully confirmed by quantum theory and evidence.

Heisenberg wrote:

One might perhaps call [the statistical nature of quantum theory] 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.” …The probability wave of Bohr, Kramers, Slater… 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…The probability function combines objective and subjective elements. It contains statements about possibilities or better tendencies (“potentia” in Aristotelian philosophy), and these statements are completely objective, they do not depend on any observer; and it contains statements about our knowledge of the system, which of course are subjective in so far as they may be different for different observers…If we compare [the quantum mechanical relationship between matter and energy] 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.

Thus, the existence of potential quantum states described by Schrodinger’s equation (which is a probability function) are the potency (the “matter”) of the system, and the collapse of the quantum waveform is the reduction of potency to act. To an Aristotelian (like Heisenberg), quantum mechanics isn’t strange at all.

Consider astrophysicist Adam Frank’s exasperation with the definition of an electron in David Klinghoffer’s post:

When I was a young physics student I once asked a professor: “What’s an electron?” His answer stunned me. “An electron,” he said, “is that to which we attribute the properties of the electron.”

Frank accurately describes one of the (apparent) paradoxes of quantum theory: subatomic particles aren’t individuated, in the sense that one can separate out electrons one from another and maintain their individuation. As Frank’s professor observed, an electron is just that which is known by its properties as an electron. That is, in Aristotelian terms, at the quantum level an electron is a kind of naked form. Its “matter” is the ensemble of quantum states described by Schrodinger’s equation that the electron can take, before it is observed (i.e., before it is known). The collapse of the quantum waveform is the reduction of potency to act.

Many of the imponderables of modern science — the strangeness of the quantum world, the intractability of the mind-body problem, the remarkable apparent directedness of convergent evolution — cease to be strange when examined from the Aristotelian perspective.

The materialist concept of “matter” corresponds roughly to the Aristotelian concept of “substance.” Aristotle noted that substances are composites of principles, and that proper understanding of these principles can make sense of otherwise unfathomable aspects of the natural world (e.g. change in Aristotle’s time, quantum mechanics in our own time).

The application of Aristotelian metaphysics to physics, biology, evolution, and neuroscience are topics I’ll explore in the future.

Photo: An oak tree, by Abrget47j (Own work) [CC BY-SA 3.0], via Wikimedia Commons.