Hylomorphism: Matter, Form, and What a Human Being Is

Hylomorphism is Aristotle's doctrine that every physical thing is a compound of matter and form: the stuff it is made of, and the organizing principle that makes that stuff the thing it is. The name joins the Greek hylē, matter, and morphē, form. Thomas Aquinas carried hylomorphism into Christian theology as an account of the human person, with the soul as the form of the body, and it remains a live rival to Cartesian dualism and to physicalism.

Its strength is the unity of the person. Its strain lies at the soul that survives the body, and at the question of who waits for the resurrection. The Many Beings Framework explains why that question presses so hard on creatures made from dust.

Key takeaways

• Hylomorphism is a theory of what a physical thing is. A material substance is matter informed by a form, with matter as potency and form as act.
• Aquinas made the soul the form of the body. The one who understands is the one who senses, and his intellectual soul is his only substantial form, a view now called hylomorphic dualism.
• Its strength is unity, and its strain is the separated soul. Thomists still dispute whether the person exists between death and resurrection, or only the soul.
• Frame-Indexed Classical Theism explains why the question is hard. Beside physicalism and Cartesian dualism, it holds that an embodied, composite nature fixes a frame in which matter seems basic, while God is spirit without parts.

What is hylomorphism?

Hylomorphism is the doctrine that every physical object is a compound of matter and form. The Stanford Encyclopedia's entry on form and matter credits it to Aristotle and notes that the doctrine "has been dubbed 'hylomorphism', a portmanteau of the Greek words for matter (hulê) and form (eidos or morphê)." Aristotle's examples are homely. Bricks become a house, bronze becomes a statue, and in each case something persists through the change while something new is acquired.

Matter is "that out of which" a thing is made. Form is, in Jeremy Skrzypek's words for 1000-Word Philosophy, "the organizing principle that makes the object what it is." The two are principles of one thing. A stack of lumber and a finished dining table can contain the same wood, and what differs between them is the form, the arrangement that lets the wood hold a meal.

The pairing of matter and form maps onto the distinction between act and potency, or potentiality and actuality. Matter is what can become something. Form is what makes it that something in fact. Change is matter taking on a form it lacked, and the matter is what carries through from before to after.

For living things the form is a pattern of activity. Skrzypek points to metabolic, homeostatic and developmental activity, and Aristotle calls the soul the form of a living body for this reason: the soul is what makes the body alive. On this view, as the Wikipedia summary puts it, "there is no problem in explaining the unity of body and soul, just as there is no problem in explaining the unity of wax and its shape." Aristotelian hylomorphism begins as physics and ends as an account of life.

What are substantial form, prime matter and the four causes?

A substantial form makes a thing the kind of thing it is, prime matter is the pure potentiality that underlies every form, and Aristotle's four causes are his four answers to why a thing is as it is. Hylomorphism distinguishes two kinds of change. When Socrates falls into a vat of dye and turns blue, he gains a property and remains Socrates. That is an accidental change, the gain of an accidental form.

When Socrates is born or dies, a substance comes into existence or passes out of it, a substantial change. A thing's accidental forms are its non-essential properties, the ones it can lose or gain without becoming a different kind of thing. The distinction explains a strange-sounding claim in Aristotle. A dead body, he holds, is only "homonymously" called a body. Once the substantial form is gone, what remains shares the living body's name and lacks its nature, because it can no longer do what a body does.

The descent through matter ends at prime matter, the matter of the elements themselves. It is "usually described as pure potentiality," able to take on any form and possessing no essential properties of its own. Aristotle "seems to leave the question of whether or not there is prime matter deliberately open," and critics have pressed the point. At best, they say, it is "a mysterious entity that we cannot know anything about," and at worst it is "said to be outright contradictory." David Oderberg and others answer that it is coherent and compatible with modern science.

Matter and form are two of the four causes. The Stanford Encyclopedia's entry on Aristotle on causality presents them as answers to four questions: the material cause answers "What is it made out of?", the formal cause "What is it?", the efficient cause "Where does change (or motion) come from?", and the final cause "What is its good?" In a bronze statue, the bronze is the material cause, the statue's form is the formal cause, the art of bronze-casting is the efficient cause, and the finished statue is the end for whose sake the work is done. Hylomorphism is the material and formal causes worked out into a theory of what a substance is.

What did Aquinas mean by the soul as the form of the body?

Aquinas took hylomorphism into his account of the human being, and it became one of the settled doctrines of Thomism. He asked whether the intellect is united to the body as its form, and he answered that it is, on a fact each reader can check. In the Summa Theologiae, First Part, Question 76, he writes that "it is one and the same man who is conscious both that he understands, and that he senses." So "the intellect which is the principle of intellectual operation is the form of the human body," and "this particular man understands, because the intellectual principle is his form."

Aquinas then holds that "there is no other substantial form in man besides the intellectual soul." The one soul that thinks is the soul that makes the body live, sense and grow, so a human being is one substance with one substantial form. Scripture records the first man as a single living being:

"Then the LORD God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being." (Genesis 2:7, NIV)

Moses records that dust and breath became one living being, and an account of the person, whatever its metaphysics, has to honour that.

Thomistic hylomorphism presses a further claim. In Question 75 Aquinas concludes that "the human soul, which is called the intellect or the mind, is something incorporeal and subsistent," and he also insists that "Man is not a soul only, but something composed of soul and body." Robert Pasnau's Stanford Encyclopedia entry on Thomas Aquinas calls this "a unique and puzzling status": the human soul "is both the form of a body and 'an incorporeal and subsistent principle.'"

Hylomorphism also tells us what God is not. In Question 3 Aquinas argues from God as pure act that "It is impossible that matter should exist in God," and concludes that "God is nowise composite, but is altogether simple." In a reply in the same question he notes that forms received in matter are individualized by it, the Thomist answer to what makes this man this man. The Scotist alternative is its own subject, taken up under haecceity.

Volume Four carries the doctrine of a God without parts through His changeless engagement with the world in Resolving Immutability & Interaction.

What is hylomorphic dualism?

Hylomorphic dualism is the name contemporary philosophers give to Aquinas's position in the philosophy of mind: the soul is the form of the body, and the human intellect is immaterial and able to subsist. David Oderberg's 2005 paper "Hylemorphic Dualism" introduces it as "the dualism of Aristotle and the Aristotelians, most notably St. Thomas Aquinas and his followers." Oderberg spells it hylemorphic, and the two spellings name one view.

Its nearest rival is substance dualism, which the Stanford Encyclopedia's entry on dualism defines as "the view that minds and bodies are fundamentally distinct kinds of substances." Its classic form, Cartesian dualism, follows Descartes in treating mind and body as "distinct substances characterised by thought … and extension respectively," where a substance is "something that can exist by itself." It sees that thinking differs from occupying space, and it must explain the traffic between the two, since "it is mysterious how the non-physical can have it in its nature to influence the physical." Oderberg observes that the idea of the mind as "a separate, immaterial substance in its own right, with only a contingent relation to the body it inhabits, is said to raise a host of problems."

On the other flank stands physicalism, which Daniel Stoljar's Stanford entry summarizes as "in slogan form, the thesis that everything is physical." Its strength is the evidence that a human being in this life is a material being whose mental life is bound up with the body. Emergentism looks for a middle way, holding that higher-level properties arise from a physical base without reducing to it. In Timothy O'Connor's words, the notion of emergence "is meant to conjoin these twin characteristics of dependence and autonomy."

Hylomorphism has its own contemporary revival. William Jaworski's Structure and the Metaphysics of Mind (2016) treats structure, in William Seager's review, as "an irreducible ontological principle," and Seager describes the view as avowedly anti-physicalist yet "entirely naturalistic." Contemporary hylomorphists differ on how much of the mind is immaterial, and Oderberg's label marks the ones who hold that the intellect is.

Where is hylomorphism strong, and where does it strain?

The strength of hylomorphism is unity, and its strain is the soul that outlasts the body. The one who understands is the one who senses, so a single subject lives the whole human life. The Cartesian question of how a mind steers a separate body does not arise in that form, because the soul is what makes this body a living human body. For a Christian who reads Genesis 2:7, that is a strong place to begin.

Beyond prime matter, the harder test is the soul that subsists. A form is ordinarily the form of something, and yet the human soul is said to exist without the matter it informs. Oderberg accepts the cost openly. A human soul must at some time be the form of a body, he argues, since "the idea of a human person disembodied throughout its history is incoherent."

The sharpest test is death. Commenting on Paul's resurrection argument in 1 Corinthians 15, Aquinas writes, as Oderberg quotes him: "My soul is not me [anima mea non est ego]; and so even if my soul should attain salvation in another life, still neither I nor any man would have attained it." If a human being is soul and body together, and the body has perished, who is there between death and resurrection?

Thomists answer two ways. Survivalists hold that the person continues to exist in the separated soul. Oderberg is one of them, arguing that "death and cessation of existence, for entities like us, are not the same event," and he reads the Corinthians line as spoken of the whole man, body and soul. Corruptionists, among them Patrick Toner, Robert Pasnau and Christina Van Dyke, read Aquinas as holding that the human being ceases to exist at death while the soul continues until the resurrection restores the person.

Each side guards something real. The survivalist guards the continuity of the one who dies in the Lord. The corruptionist guards the weight of the resurrection, which would lose its urgency if the person already enjoyed his good without a body.

Paul holds both concerns together. He writes that "we do not wish to be unclothed but to be clothed instead with our heavenly dwelling" (2 Corinthians 5:4), and a few lines later:

"We are confident, I say, and would prefer to be away from the body and at home with the Lord." (2 Corinthians 5:8, NIV)

And the hope he names is a body:

"So will it be with the resurrection of the dead. The body that is sown is perishable, it is raised imperishable; it is sown in dishonor, it is raised in glory; it is sown in weakness, it is raised in power; it is sown a natural body, it is raised a spiritual body. If there is a natural body, there is also a spiritual body." (1 Corinthians 15:42–44, NIV)

The apostle expects to be with the Lord apart from the body, calls that unclothed state undesired, and places the finished hope in resurrection. On hylomorphism, death parts what belongs together. Its difficulty is saying who waits.

Volume One sets out the two axioms behind the framework's account of natures and frames; read it free.

What does the Many Beings Framework add to hylomorphism?

Frame-Indexed Classical Theism (FICT) is a research program in analytic theology that resolves classical theological dilemmas by diagnosing them as artifacts of a single formal error, and it is the position of the Many Beings Framework. On the human person it stands beside hylomorphic dualism, Cartesian dualism and physicalism without choosing among them as accounts of human constitution, and it leaves the Thomist dispute over the separated soul unsettled. What it adds is the reason these questions press so hard on minds like ours.

The framework begins from two axioms. A being's nature is the fusion of its essential qualities, and a conscious being's mode of existence determines its mode of apprehension. The first stands close to Aristotle. The Many Beings manuscripts credit his essentialism, the claim that substances have defining natures, and define a nature as the mereological fusion of its essential qualities, one integrated whole and not a list.

A man may be tall or short, a carpenter or a king, and remain a man, because those are accidental properties. The Aristotelian line between substantial and accidental form runs straight through that definition.

The second axiom joins knowing to being, and the framework states the join in hylomorphic grammar. A being's nature and its perceptual frame, its built-in mode of apprehending reality, are related "as substance to its essential form," and a being's consciousness "is not a ghost in a machine." For us that frame is the Human Finite Frame: temporal, embodied and composite. It processes reality materially, spatially and in sequence, in terms of potentiality and actuality. To a nature like ours, materiality seems properly basic, and to lack material existence seems to be to lack existence.

That observation lets each rival keep what it sees. Physicalism reports something true of the embodied frame, where the material is what first presents itself as real, and it overreaches when "everything is physical" is said of reality as such. Cartesian dualism reports something true as well, that thinking is not extension, and it overreaches when it makes the one man two things. Hylomorphism holds the unity both of them strain, and its subsisting form strains the imagination for a reason the framework can name. An embodied frame has no native picture of form without matter.

The other term of the contrast is God. Jesus tells the woman at the well:

"God is spirit, and his worshipers must worship in the Spirit and in truth." (John 4:24, NIV)

Aquinas concludes that there is no matter in God. The framework asks for less, only that God is not composed of physical parts, and from that alone it holds that the creature is composite and God is not.

In the Absolute Metaphysical Frame, God's own mode of knowing, there is one unified reality, known without parts or succession. Our frame receives the same reality in parts and in order, because part-whole parsing is the finite intellect's native method. "Part" is the receiver's format. There is one reality and two modes of access to it, and we know the simple God truly, intellectually and not perceptually.

This account does not make the body a lesser thing, a point on which physicalism and hylomorphic dualism are both right. The framework's glorified human frame, developed in Volume Three, remains embodied, and the hope is the one Paul names, a raised body. The statement of Frame-Indexed Classical Theism sets out the axioms and the frames in one place.

Volume One derives both frames from the two axioms with each step shown; get your free copy.

How the positions compare

Each account below keeps something true about the human being, and each leaves a question open.

Frequently asked questions

What is the difference between hylomorphism and Cartesian dualism?

Cartesian dualism holds that mind and body are two substances, each "something that can exist by itself." Hylomorphism holds that a human being is one substance, matter informed by a soul, so that "Man is not a soul only, but something composed of soul and body." The Cartesian has to explain how two substances interact. The hylomorphist has to explain how the soul, which is a form, subsists when the body dies.

Is hylomorphism compatible with modern science?

Defenders of hylomorphism argue that it is. David Oderberg and others defend prime matter as coherent and compatible with modern science, and William Jaworski presents a hylomorphic view of mind that is anti-physicalist and naturalistic. William Seager's review raises the worry that such a view risks becoming a merely "polite materialism," a physicalism under another name, so the question is whether structure is irreducible.

What is prime matter?

Prime matter is the most basic matter in Aristotle's hylomorphism, the matter of the elements, "usually described as pure potentiality." It has no form of its own and can take on any form. Aristotle seems to leave open whether it exists. Critics call it unknowable or contradictory, since a thing without essential properties is hard to describe, and defenders such as Oderberg argue that it is coherent.

Does hylomorphism apply to God?

Aquinas says it does not: "It is impossible that matter should exist in God," because God is pure act, and so God is altogether simple. Frame-Indexed Classical Theism agrees that the creature is composite and God is not. Where physicalism leaves no room for spirit and Cartesian dualism treats souls and bodies as two kinds of substance, the framework reads part-whole talk as the finite mind's way of receiving a whole, so God is known under many names without being made of parts.

If matter only seems basic to us, is the body less than real?

The Many Beings Framework holds one reality, with the human frame a true and bounded mode of access to it. God formed man "from the dust of the ground," Paul hopes for a raised body, and the framework's glorified human frame remains embodied. Frame-Indexed Classical Theism differs here from physicalism, which takes matter for the whole of reality, and from Cartesian dualism, which treats the body as a substance the thinking self could exist without.

Where to go from here

Hylomorphism holds the person together. The one who reads this sentence is the one who sees the page, and Aquinas was right to build on that. Where the doctrine strains, at the soul that outlasts the body, it strains for creatures whose nature makes matter the first thing they take for real. The Many Beings Framework names that nature and its frame, and it leaves the waiting soul where Scripture and the tradition leave it.

Volume One sets out the two axioms and derives the frames, and it is free to download. Volume Four, Resolving Immutability & Interaction, takes the framework into divine simplicity and changelessness, and it is available now in every format. The rest of the series carries the same frames through free will, evil and time.

Related reading

• Is God a Person? Classical Theism vs Theistic Personalism
• Nominalism