Metaphysics for Beginners

The word looks forbidding, but the thing is simple. Metaphysics is the study of being as being — the study of what it means for anything at all to exist. Not what it means to be a tree, or a star, or a man in particular; that is the work of botany, astronomy, and medicine. Metaphysics asks the question underneath all of those: what does it mean simply to be?

Everything you will ever meet falls into one of two conditions. Either it is real being — something that actually exists, like the chair you are sitting in, a friend, a mountain — or it is merely imagined, like a unicorn or next year's birthday. Metaphysics begins with the real. The branch of it that studies what kinds of things exist and how they are related and ranked is called ontology, from the Greek word for being.

That is the journey of this page in one sentence: we will look closely at ordinary things until they hand us the question they cannot answer, and then we will see where that question leads.

Reality is not flat. In the vision St. Thomas inherited and perfected, all that exists is arranged in a great order — a hierarchy of three levels, each existing in a fuller or thinner way than the next.

The order is not arbitrary. It is a ladder of participation in being — a word we will return to. God is being; angels have being without matter; we material creatures have being through the joining of matter and form. Hold this ladder in mind; nearly everything that follows is a closer look at one of its rungs.

Take any single thing in the material world and ask three plain questions about it: What is it? What is it made of? And what about it can change? The answers reveal four pairs of ideas that make up the inner architecture of everything that exists.

A. Essence and Existence — essentia et esse

This is the very heart of Thomistic metaphysics, and once it clicks, much of the rest follows. There is a real difference between what a thing is and that it is.

The essence of a thing is its whatness — the kind of thing it is. The essence of a triangle is to have three sides; the essence of man is to be a "rational animal." You can know perfectly well what a phoenix is without a single phoenix ever existing. That tells you essence is one thing.

The existence of a thing — its esse, its very act of being — is the altogether different fact that it is really there. Not the idea of a triangle, but this triangle drawn on this page. Not a character in a story, but John Doe, a living man at a real address.

Here is the decisive point: in every creature, essence and existence are really distinct. Nothing in the nature of a man, or a tree, or a galaxy requires that it exist. Each one might just as easily never have been. That is why we call creatures contingent — they need not be. Their existence is received, not owned.

B. Act and Potency — actus et potentia

How can anything change and still remain itself? An acorn becomes an oak; cold water becomes warm. Aristotle's answer, taken up by Aquinas, is the pair act and potency.

Act (actus) is what a thing actually is right now — its realization, its perfection. Potency (potentia) is what a thing could become — a real capacity, but not yet fulfilled. The acorn is actually an acorn and potentially an oak. The cold water is actually cold and potentially warm.

Change, then, is simply the passage from potency to act. And there is a rule with vast consequences: a potency is only ever made actual by something already in act. Cold water does not warm itself; fire, already hot, warms it. Run that backward far enough and you arrive at something that is pure act with no unrealized potential whatsoever — and that is God, who needs nothing actualized in Him because He already is everything He can be. He alone never changes.

C. Substance and Accident

A man may grow tan in summer, lose weight, learn Greek, sit then stand — and through all of it he remains the same man. The deep, abiding core that makes a thing itself is its substance: what exists in its own right, not in another. The changeable features — color, size, posture, knowledge — are accidents: real qualities, but ones that lean on the substance and cannot stand alone.

Accidents need a substance to exist in; a substance can shed this or that accident and endure. (The one miraculous exception the Church confesses is the Holy Eucharist, where the accidents of bread and wine remain after their substance has been changed into the Body and Blood of Christ — a mystery that this very distinction allows us to even speak about.)

D. Matter and Form — Hylomorphism

Every material thing is a union of two principles. Matter (materia) is the raw stuff — the wood, the bronze, the flesh; it is the principle of potentiality, the "could-be." Form (forma) is the organizing pattern that makes the stuff into this definite thing rather than that; it is the principle of actuality and the source of a thing's intelligibility. The doctrine that bodies are matter-and-form together is called hylomorphism, from the Greek hyle (matter) and morphe (form).

A bronze statue is bronze (matter) shaped into a figure (form). A living body is flesh (matter) organized by its soul (form) — for in Aquinas, the soul simply is the form of a living thing. Hold that thought; it returns when we come to the human person.

Aristotle noticed that whenever we say anything true about a thing, our statement falls into one of exactly ten patterns. He called these the ten categories. The first, substance, names what a thing is. The other nine are all accidents — the various ways something can be about a substance.

The list is not trivia. It is a complete map of every way being can be predicated of a thing — and it shows that all nine accidents only exist by leaning on the one category that stands on its own: substance.

When we ask why a thing exists, we may be asking any of four different questions. Aristotle named them the four causes, and they are best learned all at once from a single example — a bronze statue.

Behind all four stands a principle the mind cannot deny: every effect has a cause; whatever is moved is moved by another; nothing gives what it does not have; and — in the old Latin tag — ex nihilo nihil fit, "from nothing, nothing comes."

Of the four, the final cause is quietly the most important. Aquinas calls it the "cause of causes," because the sculptor only picks up his tools for the sake of the finished statue, and only chooses that shape for the sake of the honour intended. Remove purpose from the world and the whole structure of cause and effect collapses into meaningless motion. That things act for ends — that the universe is shot through with purpose — will become, in the Fifth Way, a road straight to God.

Some features belong not to this or that kind of thing, but to everything that exists, simply because it exists. They are called the transcendentals — from the Latin transcendere, "to climb over all boundaries" — because they overflow every category and apply to all being whatsoever.

The deepest claim here is that these are convertible — being, oneness, truth, goodness, and beauty are really one and the same reality, differing only in how we think of them. To exist is to be one, and true, and good, and beautiful. They are five names for the single light that pours from God, who is Being, Unity, Truth, Goodness, and Beauty itself.

Aquinas adds that beauty in particular requires three things: integrity (nothing missing), proportion (the parts in right harmony), and clarity (the radiance of the form shining through the matter). It is no small thing that the same God who is Truth is also Beauty — the faith has never been embarrassed by either.

A problem now presses on us. We say a stone "is," an angel "is," and God "is." Do we mean the same thing by that little word "is" in each case?

If we mean exactly the same thing — speaking univocally — then God would be merely one more being among beings, the same kind of thing as a stone, only bigger. That is a kind of disguised idolatry. But if we mean something completely different — speaking equivocally — then our words about God would be empty noise, and we could say nothing true of Him at all.

St. Thomas threads the needle with the analogy of being. When we say God "is" wise or "is" good, our words are neither identical to nor unrelated to their meaning when applied to creatures. They are analogous — bearing a real but proportional likeness. As a creature's goodness is to a creature, so God's goodness is to God — only without the limits. The likeness is genuine, so our words are true; the difference is infinite, so we are never tempted to drag God down to our scale. This is the grammar that makes all sober talk of God possible.

To participate is to have partially what another has fully. A hot iron has heat; the fire is the source of heat from which the iron borrows. So it is with existence itself. God is Being — Ipsum Esse Subsistens. Every creature merely has being, on loan, by participation. Nothing in creation possesses existence by its own right; all of it receives existence, moment by moment, from the One who is existence.

This is why being comes in degrees. A thing participates more or less fully in being according to its place on the ladder we began with:

The whole vast creation, top to bottom, is a single great act of receiving — every creature held out over nothingness by the hand of the Giver.

Everything so far has been preparation for the question metaphysics cannot avoid: if the whole world of changing, contingent, ordered things cannot explain its own existence, what does? St. Thomas offers five paths — the famous Five Ways — each beginning from something anyone can observe and reasoning to God. They are not five gods but five roads to the one God.

Each way ends at something the world by itself cannot supply. And reflection then shows that the Unmoved Mover, the First Cause, the Necessary Being, the Highest Perfection, and the Supreme Intelligence are not five strangers but one and the same — the God whom Israel knew and whom the Word reveals. Reason walks us to the door; revelation tells us His Name.

Because God infinitely exceeds anything we can picture, the surest knowledge of Him often comes by saying what He is not. This is the ancient via negativa, the way of negation — and each denial yields a truth:

From these flow the divine attributes the Church confesses: simplicity (no composition of any kind), perfection (He lacks nothing), infinity, immutability (for change would mean unrealized potential, and God is pure act), eternity — which Boethius beautifully defined as "the simultaneously whole and perfect possession of unending life" — and unity: there is, and can be, only one God.

And this God is not a distant abstraction. He knows all things perfectly; He wills His own goodness of necessity and creatures freely; His love is the very cause of whatever goodness any creature has; and His providence orders all things gently to their end.

To create is to give being from no pre-existing material whatsoever — creatio ex nihilo, creation from nothing. A carpenter makes a table from wood; a baker makes bread from grain. Neither truly creates. Only God can give existence absolutely, with no "stuff" to start from. Creatures can transform; only God can create.

Nor is creation a single event safely behind us. God does not light the world like a lamp and walk away. He holds it in being at every instant — what the tradition calls conservatio, conservation. Were He to withdraw His sustaining will for one moment, creation would not break or decay; it would simply cease, as a song ceases the instant the singer falls silent.

And God creates with intelligence, according to the ideas in His own mind — the exemplar cause of all things. Here metaphysics brushes against the Gospel, for those divine ideas reside in the eternal Word: "All things were made by him." Every creature is, in a real sense, a word spoken by the Word. God's purpose in all of it is the free overflow of His own goodness — His glory — which each creature renders simply by being fully what He made it to be.

Now the framework comes home, for you are a metaphysical wonder. Recall that in living things the soul is the form of the body. So in man: the soul is the substantial form of the body. You are not a ghost piloting a machine, nor a body that happens to think. You are one substance — body and soul together — a single living whole. This is why the Church insists on the resurrection of the body and not merely the survival of a spirit.

What sets the human soul apart is that it is rational: capable of intellect (grasping truth) and will (choosing the good). And here is the hinge of human dignity — these two operations are immaterial. Thought is not weighed in grams; a choice has no colour. Because the soul performs acts that do not depend on matter, the soul does not depend on matter for its existence. Therefore, when the body dies, the rational soul does not. The human soul is immortal.

By nature we are, in the old definition, "rational animals" — sharing life and sense with the beasts (our genus, animal) but marked off by reason (our species, human). Yet we are more than a clever animal, for we are made in the image of God — imago Dei. The mind even bears a faint print of the Trinity in its three great powers:

You are, in St. Thomas's phrase, capax Dei — "capable of God," made with a capacity that nothing less than God can fill.

Above us on the ladder stand the angels — pure spirits with no matter of any kind. This single fact has a striking consequence. For us, many individuals can share one nature (there are billions of humans, all of one species) precisely because matter divides the one human form among many bodies. But an angel has no matter to be divided. So each angel is its very own species — a complete and unrepeatable kind of being, differing from every other not by degree but by essence. Where men are unique individuals within one species, angels are unique species, each entire.

Tradition arranges the heavenly host into nine choirs in three triads — Seraphim, Cherubim, and Thrones nearest to God; Dominions, Virtues, and Powers governing creation; Principalities, Archangels, and Angels nearest to us, among them the guardian angel given to every soul. These choirs name roles and ranks, not shared natures — for each angel remains its own species even within its choir.

We can now see where the long climb has led. Follow the thread: Being is intelligible — the world makes sense, it can be understood. But what is intelligible must be grounded in an Intellect. Created things receive their being and their order from a higher source, and that source is the divine ideas in the mind of God. And those ideas live in the eternal Word — for "all things were made through him."

So metaphysics, walking only by the natural light of reason, arrives at the very threshold of the Gospel. It cannot open the door — only Christ does that — but it brings the layman to it and lets him knock with confidence. This is the deepest reason the Church has always honoured philosophy: not as a rival to faith, but as its servant and forerunner.

In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made. — S. John 1:1–3

This is why none of these terms is dry or distant. To know that things truly exist, that they are good and intelligible, that they are caused and held in being, that the soul is immortal and made for God — this is to read creation as what it is: the first book God ever wrote, every page of it spelling the Word. And it is why the corruption of language and the denial of truth are never harmless fashions. To sever the mind from reality is, in the end, to sever it from the Logos in whom all reality holds together.

Begin, then, where you are. Look at the chair, the tree, the friend, your own restless mind — and let the things that are made lead you, as Scripture promises they will, to the One who made them.

A pocket reference. Open it whenever a Latin word ahead has slipped its meaning.