What Is Matter (and Why Does It Matter)?

Everyday experience presents us with a world of tables, chairs, rocks, trees, dogs, cats, apples, and oranges. Common sense takes such things to be paradigm cases of material objects. What is material or physical is, for the man on the street, what we can see, hear, taste, touch, or smell. And objects like those mentioned—with their variety of colors, sounds, odors, flavors, and other perceptible qualities—are the most obvious examples.

Said man is also aware that these things are made up of parts, and that those parts have parts of their own. But he thinks of these parts as parts (rather than as independent entities in their own right) and as just smaller instances of things of the same kind as the ordinary objects referred to. That is to say, he thinks of them as having a certain size, shape, and color, as located at a specific place and moving at a certain speed, and so on. And while it occurs to him that at some level these parts are not visible to the naked eye or otherwise directly percepible, his natural tendency is to think of them as nevertheless very much like the visible things.

So too is our man on the street aware that there is a larger universe beyond this everyday world. He’s heard tell of planets and solar systems, galaxies and galaxy clusters, distant objects like black holes and events in the distant past such as the Big Bang. But his natural tendency is to model these too on the familiar world of daily experience—to think of the universe and the objects that fill it as like the things that surround us in everyday life, only bigger. When he conceptualizes either the very large or the very small, he does so by thinking of them on the analogy of the middle-range objects that the senses present to him.

Common sense also takes these middle-range physical objects to have natures that sharply distinguish them from each other and afford them stability over time. Stone is just a different sort of thing from wood, and a dog is a different sort of thing from a bird. These differences manifest themselves in certain facts: wood will burn when you apply a lit match to it and stone will not; birds build nests and hunt for worms and dogs don’t. And the differences persist through changes in superficial traits. You can paint a stone and thereby change its color, but you won’t thereby have made it any less a stone so long as it retains distinctively stone-like qualities like solidity and durability. A dog starts out as a sprightly puppy and may end up gray and lethargic, but it will still wag its tail when you set dinner before it and may even remain inclined to chase a thrown ball in a way a bird never will.

Common sense also associates the natures of many things with distinctive purposes, which it regards as pervading at least the living world. By nature, birds aim at building nests and finding worms for their young, by nature eyes are for seeing and legs for walking, by nature a plant’s roots seek out water, and so on.

Thus speaks common sense. But is it right? How does it relate to what modern science tells us about the nature of matter? And are these questions of more than academic interest? Philosophers have defended a variety of answers, but three in particular are especially relevant for our purposes. The first is the view of thinkers like Aristotle and Thomas Aquinas that common sense is basically correct, albeit in need of a deeper articulation and correction around the edges. Their position is known as hylomorphism, and Robert C. Koons develops an intriguing new defense of it in his book Is St. Thomas’s Aristotelian Philosophy of Nature Obsolete?

Atomism and Monism

Hylomorphism is best explained by contrast with the other two views, though. The second is known as atomism, first developed by ancient Greek philosophers like Leucippus and Democritus, and revived in a variety of modified forms by early modern thinkers associated with the Scientific Revolution (such as Galileo and Robert Boyle, whose variation came to be called “corpuscularianism”). For atomism, the material world is made up of innumerably many unobservable particles that are radically different from the objects of everyday experience. In particular, they are colorless, soundless, odorless, tasteless, and devoid of heat or cold. In fact, traits like color and taste are “secondary qualities” (as they came to be called), and they do not exist anywhere in the material world, at least not in the manner common sense supposes. Rather, when experiencing physical things, we project these qualities onto them and wrongly suppose that we are perceiving something that is really out there (just as someone looking at the world through rose-colored glasses might wrongly suppose that the redness he sees is really in the world rather than just in the glasses).

In the atomist view, there is no sharp distinction in reality between stone and wood, a dog and a bird, or any other material things. At bottom they are really all just the same sort of thing, namely masses of colorless, odorless, tasteless, soundless particles. The differences are in degree rather than kind, a matter of how particles of the same basic character are arranged. Hence, as with two sandcastles of different shapes, the differences between a stone, a piece of wood, a dog, and a bird are ultimately superficial.

Nor are there any genuine purposes in nature. Masses of particles push and pull one another, and when they do so in patterns that are sufficiently complex (as in living things), they behave as if they acted for some purpose. But really they don’t. Purpose—like color, sound, odor, taste, and the like—is just something we project onto nature rather than existing independently of our minds. For atomism, then, common sense is deeply mistaken about the true nature of the material world. This is also the judgment of the third philosophical view, which is known as monism and was first defended by ancient Greek philosophers like Parmenides and Heraclitus. According to monism, our ordinary experience of the world, which seems to reveal a wide variety of distinct material objects, is illusory. There is in reality only one thing, the universe as a whole. Just as the color, size, shape, and weight of a stone are mere modifications of the stone rather than entities in their own right, so too, for monism, are tables, chairs, rocks, trees, dogs, and cats and people mere modifications of the one big entity that is the universe.

Modern particle physics is widely assumed to have vindicated the core claims of atomism. Meanwhile, Einstein’s general theory of relativity is sometimes claimed to have established a version of monism, insofar as it is often interpreted as entailing that the universe is a single, four-dimensional block (with time being a fourth dimension added to the three familiar spatial ones). As Koons argues, if either of these claims were correct, the implications for philosophy, theology, morality, and indeed science itself would be profound and dire.

If either atomism or monism were true, reality would not be the way our senses present it as being. The world of ordinary middle-range objects would be unreal, and only either collections of particles, or the universe considered as one big lump, would actually exist. One implication is that there would not really be anything having the natures and purposes we take these middle-range objects to have—including human beings. And if there is nothing with a distinctively human nature, there can be no foundation in our nature for morality (as the natural law tradition in ethics takes there to be). Certain theological doctrines would be undermined as well. For example, as Koons points out, there would be nothing having the natures of the bread and wine which, according to the Catholic doctrine of transubstantiation, are transformed into the body and blood of Christ in the Mass.

Of course, many skeptics would be happy to accept such implications, and claim that they follow from science. But as Koons points out, science itself is also undermined in either an atomist or a monist view. For there would also be nothing having the natures and purposes that we take our sense organs to have. Hence we would have no reason to believe that the world the senses present to us in any way corresponds to what is really out there—in which case, all the observational and experimental evidence on which science is based would be as illusory as everything else.

Hylomorphism

Hylomorphism, by contrast, holds that the way our sensory experiences carve up reality more or less corresponds to what is really out there. Indeed, it takes these ordinary objects (rather than either particles or the universe as a whole) to be the fundamental constituents of the material world. The term “hylomorphism” derives from Greek words for matter and form. The basic idea is that every physical object is composed of matter and form. In this view, matter, considered just by itself, is indeterminate and merely potentially a thing of a certain kind. A form, meanwhile, is a nature or essence that might be shared by multiple instances of a kind (as the forms of being a stone, a tree, a dog, or a human being are). Form is what actualizes matter’s potential to be a thing of a certain kind, making of it something determinate—this particular stone, that particular dog, or what have you.

According to hylomorphism, the parts of a material thing are less fundamental to it than the whole—and, indeed, exist in the whole only as potentially independent things rather than as actual entities in their own right. For example, hydrogen and oxygen exist in water, but only as constituents of the water rather than as entities in their own right. They potentially have such independent existence (via electrolysis), but until that happens what actually exists is the water as a whole substance. A dog’s eyes and paws exist, but only as parts of the overall organism, and indeed cannot properly be understood except in terms of the role they play relative to the whole animal. While in their normal state they are only potentially rather than actually entities in their own right.

For hylomorphism, then, atomism is mistaken to take particles to be the fundamental realities, and ordinary objects to be mere aggregates of particles. Rather, the ordinary objects themselves are the fundamental entities, and their constituent particles, like other parts, exist in them only as potentially independent entities. In this way, the whole is not only more than the sum of its parts, but more real than the parts. Meanwhile, the larger universe is merely the sum of the ordinary middle-range objects that make it up—contrary to monism’s claim that the universe as one big lump is the only fundamental entity (with ordinary objects being mere modifications of it). Thus does hylomorphism endorse the metaphysics of common sense.

Quantum Hylomorphism

What is most original in Koons’s book is his argument that quantum mechanics is best interpreted as vindicating the Aristotelian hylomorphist’s view of nature. To be sure, there have been others who have made such claims, not the least of them being Werner Heisenberg, one of the fathers of modern quantum physics. But Koons is the first prominent philosopher to make the case at book-length, in a way that combines expertise in the relevant philosophical ideas and literature with serious and detailed engagement with the scientific concepts. Future work on hylomorphism and the philosophy of quantum mechanics will have to take account of his arguments.

As Koons notes, there are several aspects of quantum mechanics that lend themselves to an Aristotelian interpretation. For example, there is Heisenberg’s famous principle that the position and momentum of a particle are indeterminate apart from interaction with a system at the middle-range level of everyday objects (such as an observer). There is physicist Richard Feynman’s “sum over histories” method, in which predictions must take account of every possible path a particle might take, not just its actual path. There are “entanglement” phenomena, in which the properties of a system of particles are irreducible to the particles considered individually or their spatial relations and relative velocity. There is quantum statistics, in which particles of the same kind are treated as fused and losing their individuality within a larger system. What such examples indicate is that matter at the smallest scales has precisely the kind of potentiality and indeterminacy that hylomorphism attributes to it, and that it is only the higher-level features of physical systems that actualize that potentiality and make of matter something determinate (which is the role hylomorphism attributes to form).

But this merely scratches the surface of Koons’s analysis. The meat of the book is a sustained critique of several well-known interpretations of quantum mechanics (such as David Bohm’s pilot wave interpretation, Hugh Everett’s many-worlds interpretation, objective collapse theories, and the standard reading of the Copenhagen interpretation). Koons points out grave difficulties facing each, which in some cases include incoherences like those referred to above (insofar as they cannot make sense of the reality of the everyday world of experience that provides the empirical evidence for affirming quantum mechanics in the first place). He proposes in their place what he calls “quantum hylomorphism,” which has the advantage of resolving some notorious puzzles facing quantum theory no less than it vindicates hylomorphism.

Some Thomist, I’m not sure who (it may have been Ralph McInerny), once remarked that whenever you have a new idea, you should check Aristotle to see what he already said about it 2300 years ago. Koons makes a powerful case that this is true even of quantum mechanics, or at least of the heart of quantum theory’s conception of matter. And he makes it clear why this matters to wide-ranging issues in philosophy, science, and even ethics and theology.