The Real Presence of our Lord and Savior Jesus Christ in the Holy Eucharist is among the greatest mysteries of our faith. Indeed, the priest celebrating the traditional Roman Rite whispers in the midst of consecrating the Precious Blood, “Mysterium fidei.” Over the millennia, the Catholic Church has lovingly pondered this mystery, and her great theologians, while humbly acknowledging reason’s limits in probing what is divine and supernatural, have nevertheless been able to offer a reasoned defense of it against all objections that unbelief and heresy have hurled against it.
In the modern world, where materialism, scientism, and skepticism reign supreme, the mysterious change that the Church calls transubstantiation has its mockers and would-be debunkers — even conscientious or de facto dissenters within the ranks of the Church, such as the modernists who populate many a Catholic university, seminary, or chancery. As Catholics who seek to understand and live our faith more deeply, we need to take hold of the commonsense philosophy of reality that provides the Church with raw materials for dogmatic definitions. If we do this, we stand a better chance of achieving clear thinking about this wondrous work of God and thus of being in a position to speak of it to others.
It is for this reason that I offer to readers of OnePeterFive a beginner’s guide to transubstantiation. This is not going to be easy reading. The mysteries of the faith challenge our finite and feeble reason to breaking point — but without breaking it. Unlike a bodily muscle that gets tired or even damaged with use, our minds get stronger the more we exercise them, as Aristotle pointed out long ago. I mention Aristotle, the rational philosopher par excellence, not only because he’s my favorite Greek philosopher (everyone ought to have a favorite), but because, as a matter of fact, he bequeathed to St. Thomas Aquinas the conceptual tools for discussing transubstantiation. The mystery, while never ceasing to be a marvel and a miracle past all human thought, can be clarified to the mind so that it no longer seems a colossal contradiction or impossibility.
A Short Philosophical Primer
As the distinction between “substance” and “accident” is fundamental to the Church’s teaching on transubstantiation, anyone seeking a deeper understanding of the sacred mysteries will do well to spend a little time on what these terms refer to.
The distinction between substance and accident, in spite of the technical sound of the terms, is founded on everyday experience. While modern usage often restricts the meaning of “substance” to elements or chemicals and “accident” to an unintended and usually harmful event, their philosophical meaning is much wider. The word “substance” refers to any individual being, anything that exists in and of itself — e.g., a man, a horse, a plant, a stone — having its own proper nature (in contrast to a bench, for example, which, though it has a definition, does not have its own proper nature, but is the result of art putting together different natural substances). The term “substance” derives from its function: it is “that which stands under” (Lt. substantia, Gk. hypostasis), in contrast to the “accidental” (Lt. accidens, Gk. katasymbebekos), “that which befalls, happens to, belongs to” substance. A substance exists in itself as opposed to what exists in a substance. Color, shape, weight, knowledge, virtue, fatherhood, sonship are examples of things that exist in a substance and not in themselves. Color, shape, and weight truly exist, but they exist as belonging to something that is colored, shaped, or weighted. We never see whiteness, but rather a white horse or a white chair; we never see justice, but rather a just man or a just law [i]. When we say someone is six feet tall, we mean that his size is a quantity of his substance; he is six feet tall. Fatherhood is not something that exists apart from someone who is a father; “being a father” belongs to one person in relation to another. Knowledge has existence only in the mind of him who possesses it; it is an accident inhering in his soul.
There are two kinds of accidents: accidents generally so called (non-proper accidents) and proper accidents, also known as properties. Non-proper accidents can come to be and pass away in the same substance, as a pale man can become dark by tanning, or an unmusical man can become musical and through lack of practice can lose that habit. A proper accident, on the other hand, is rooted in and flows from the nature of a substance so that it is always present when the substance is present — e.g., the ability to laugh or the ability to speak, which flow from man’s rational nature. These are called accidents because they exist only in a substance, but they are called properties because they are proper to a certain kind of substance and always accompany it. It would be wrong, therefore, to define “accident” as that which can either be or not be; some accidents are permanent, others mutable. The important notion in defining “accident” is that it exists in, or inheres in, an underlying subject. (The sole exception is the mystery of the Eucharist, where, by divine power, the accidents of bread and wine exist without an underlying subject, as we shall discuss below.) Accidents are thus always distinct from substance, which is their source of being. If there were no rational animal, there would be no foundation for the properties of speech and laughter or the accidents of tall, brave, musical, etc. [ii].
Because we gain our knowledge of reality through our senses, we can directly perceive only the accidental features of things. Nevertheless, the existence of substance is readily inferred from our experience of individual beings (this man, this horse) and from the impossibility of an abstract quality (whiteness, musicality, justice, six-footedness) existing apart from a subject or individual modified by it. The accidents we perceive point to a more fundamental level of being that enables them to exist. A person can change color or height, can acquire or lose virtue, without ceasing to be the same person; substance is the permanent principle underlying all other characteristics.
This leads us to a broader meaning of substance: that which truly is, the essential foundation, as opposed to what is mutable or derivative. In this sense, the nature or essence of a thing is sometimes called its substance, because the nature or essence is that which makes a thing to be what it is — and by extension, the being of a thing can be called substance. When “substance” is used in these extended senses, it no longer signifies a counterpart to or foundation of accidents; hence, when God is called a substance, or the Persons of the Trinity are referred to as hypostases, or when we speak of the hypostatic union of the human and divine natures in Jesus Christ, we do not imply that there are corresponding accidents inhering in the being of God or the Word. Things that are accidents in the soul of a rational creature (such as its knowledge and virtues) are, in God, identical with His being.
The term “substance” entered into Christian theology very early on, in controversies surrounding the Incarnation and the Blessed Trinity. The Council of Nicaea (325), defending the divinity of Christ, speaks of the Son as homoousian (Lt. consubstantialis) — that is, of the same substance, the same divine essence — against the Arians, who called Him homoiousian, “of a like substance” [iii]. In the Middle Ages, when the mystery of the Eucharist as the real Body and Blood of Christ was challenged by Berengarius of Tours, the vocabulary of substance and accident was employed to formulate the orthodox teaching.
The Miracle of Transubstantiation
As the central mystery of our faith, “the font and apex of the Christian life,” the Holy Eucharist is the object of the Church’s most profound adoration and most rigorous vigilance [iv]. To understand why the Church uses the term “transubstantiation” for the miracle that occurs at the moment of consecration, two truths are presupposed: first, that the Eucharist really is the Body and Blood of Christ, and second, as a necessary counterpart, that bread and wine really change into the Body and Blood.
Both truths are taught in Scripture [v] and unequivocally attested to by the Eastern and Western Fathers of the Church. Greek authors refer to the change that takes place in the gifts as a metousiosis or change of one being (ousia) into another; to this day, Eastern Orthodox theologians who remain faithful to the Patristic heritage are fundamentally in agreement with Catholic dogma, even if they use a different and less precise terminology [vi]. The Latin term transubstantiatio appeared in the late eleventh century and was set forth authoritatively at the Fourth Lateran Council (1215). Opposing the Eucharistic heresies of the self-styled Reformers, the Council of Trent (1545–1563) solemnly restated the doctrine, noting that its meaning, if not the special term, has been the common faith of the Church always and everywhere.
The substance of a thing is what it most fundamentally is as a certain kind of thing (e.g., bread is a product of baked flour, oil, salt, etc.), as distinguished from its various accidents or characteristics (color, taste, smell, shape, size, location, and the like) [vii]. Normally, the accidents of a thing indicate its substance; the color and taste of bread lead us to make the unsurprising inference that it is bread. Transubstantiation is rightly called miraculous in the strongest sense — that is, altogether outside the ordinary course of nature — because in this mysterious conversion, the accidents or characteristics of bread and wine remain while the inner substance, the essential reality, comes to be entirely different. As the Council of Trent teaches, at the moment of consecration, in virtue of the efficacious words of our Lord uttered by His minister, the entire substance of bread is changed into the entire substance of the Body of Christ and the entire substance of wine is changed into the entire substance of the Blood of Christ. Bread and wine as such cease to exist, and the full reality of Christ comes to be present under their appearances, which, by remaining, permit us to consume the divine gifts. The accidents of bread and wine thus remain without any substance in which they inhere, and the substance of Jesus Christ becomes present without His accidents or characteristics being sensible to us.
One must marvel at the beautiful fittingness of the means chosen by our Lord: bread and wine are evident sources of nourishment for the body, thus perfectly symbolizing the spiritual nourishment the soul receives in Holy Communion, and the lingering accidents of these foods permit the communicant to receive the true flesh and blood of the Lord, and thus His soul and divinity, unbloodily, in a manner well suited to us and our powers. When we receive Holy Communion, the Lord of Heaven and Earth comes to dwell within us in the most intimate way, blessing our souls and bodies with the holiness of His divinized humanity. While the human body transforms ordinary food into its own substance, in receiving Christ worthily it is we who, bathed in His grace, are transformed by degrees into His image and likeness.
Because through the words of consecration the Body and Blood of Our Lord come to be present in all their truth, as the living flesh and blood of the risen Lord in Heaven, the consecrated host necessarily also contains — “by concomitance,” to use the language of Saint Thomas and the Council of Trent — His Blood, Soul, and Divinity, for the latter are inseparable from the former [viii]. They always accompany the Body (the verb concomitare simply meaning to attend, accompany, go along with). The same is true in regard to the wine, which is made the Blood of Christ by virtue of the words of consecration, but in which are present, by concomitance, the Savior’s Body, Soul, and Divinity. This is the reason why reception under one species, whether that of bread or that of wine, does not in any way lessen one’s reception of the whole Christ, the Word made flesh, even if the signification or sign-value of the sacrament is more complete in reception under both species, which the Catholic Church has seen fit to limit to the priest who offers the sacrifice [ix].
Objections and Replies
Some have objected that the use of “substance and accident” in defining the mystery of the Eucharist makes an illegitimate use of pagan philosophical categories that are not revealed in Scripture or found explicitly prior to the scholastic thinkers of the Middle Ages. In her efforts to defend this holiest of mysteries, the Church, so it is said, tied herself to debatable human distinctions instead of remaining content with a simple act of faith in the presence of Christ.
One might initially reply that the terms “Incarnation” and “Trinity” are also not mentioned in Scripture but are no less true on that account. But more to the point, this objection fails to see that the distinction between substance and accident derives from common experience and the structure of reality. The Church uses philosophical terminology whenever it captures some undeniable truth about the world we live in or the faith we profess. In his 1965 encyclical Mysterium Fidei, Pope Paul VI explained that the Church has found a universal language with which she can successfully present and defend her teachings:
These formulas [of Trent] — like the others that the Church used to propose the dogmas of faith — express concepts that are not tied to a certain specific form of human culture, or to a certain level of scientific progress, or to one or another theological school. Instead they set forth what the human mind grasps of reality through necessary and universal experience and what it expresses in apt and exact words, whether it be in ordinary or more refined language. For this reason, these formulas are adapted to all men of all times and all places.
Even if the Church does not enjoin Aristotelian physics per se, she perceives that the mystery of the Eucharist can be correctly defined in terms originally introduced by Aristotle. She has solemnly defined that the wondrous and singular change occurring at the moment of consecration is most appropriately and correctly called transubstantiation. Responding to the Synod of Pistoia (1786), which held that the theory of transubstantiation is a “purely scholastic question,” Pope Pius VI reaffirmed to the contrary that all of the faithful should be instructed in it.
Paul VI’s Mysterium Fidei issued a stern warning against devaluing or replacing the term “transubstantiation,” condemning in particular two innovations, “transfinalization” (namely, that the words of consecration change the finality or purpose of the bread and wine, which then serve the function of stimulating faith in Christ’s love) and “transignification” (that the words of consecration change the meaning of the bread and wine, which thus acquire a symbolic significance lacking in ordinary human food). Such theories hearken back to the errors of Protestant Reformers who either denied the actual conversion of bread and wine into the Body and Blood of Christ and consequently rejected the Real Presence or denied the total conversion of the gifts, insisting that after consecration, the bread and wine continue to remain, together with or alongside of the newly present Body and Blood (a theory known as consubstantiation). It was precisely such heresies that the Council of Trent anathematized in order to safeguard the profoundest mystery of divine love. When she rejects consubstantiation, moreover, the Church is in fact upholding reason, for to say that the very same thing is both the entire substance of Christ and the entire substance of bread is a contradiction in terms, a metaphysical impossibility.
Another objection runs as follows: isn’t God “deceiving” us if Jesus Christ is truly present but cannot be perceived in any way as present? Why would the Savior choose to give Himself to us under different and misleading appearances?
The practical answer is that, granting our Lord’s intention to nourish us with Himself, we could not eat His Body and drink His Blood in a dignified way unless it were made available after the manner of ordinary food and drink. But the deeper answer is that the Eucharist, as the supreme mystery of faith, beckons us to place our entire trust in the inerrant Word of God, the God of mercy who condescended to enter the world as a helpless infant whose divinity could not be recognized by human senses (Jn. 1:9–13, Mt. 16:17). The hidden presence of Christ upon the altar is at once the greatest mercy to sinners (Mt. 26:28) and the greatest challenge to disciples, who must discern Christ in the breaking of the bread (Lk. 24:35) or they shall find Him nowhere, even were He to appear and walk alongside them. If we must exercise the supernatural virtue of faith to accept all the mysteries of our holy religion — the Trinity, the Incarnation, the virgin birth, the resurrection — we must exercise this virtue above all when worshiping and approaching the God hidden under the humble appearances of the consecrated gifts. Our Lord said to Thomas: “Blessed are they who have not seen and yet believe” that I am truly risen from the dead (Jn. 20:29); to us at every Mass He says: “Blessed are you who do not see and yet believe” that I am truly here, in your midst, fulfilling my promise to be “with you always even to the end of time” (Mt. 28:20).
A philosophically minded person could object that a substance cannot change without its accidents or appearances also changing; thus, if bread and wine cease to be, their appearance must also cease, and if Jesus comes to be present, His appearance must also come to be present.
St. Thomas replies: God is the first and absolute cause of all being — the being of substances as well as of their accidents — and whatever is the first and absolute cause of a composite is also the cause of its aspects or components taken one by one. Thus, He is able, in His omnipotence, to cause a substance to exist by itself without its usual sensible characteristics, and to sustain accidents in being apart from their customary subject,. The Creator who causes both iron and its accidents (shiny surface, hardness, durability) to exist and remain in existence can, if He chooses, cause the characteristics of iron to remain while withdrawing the substance underlying them. That He can do so should not be difficult to accept when we consider that God, in creating the world, the angels, and each human soul, brings forth being out of nothing (ex nihilo) — an act that surpasses every miracle. The objection is valid only so far as our common experience goes, for the Eucharist is an absolute exception, about which we have to be instructed by Our Lord and His apostles. With all other beings, it is true that substance and accidents always go together, but in the mystery of the Blessed Sacrament, God has willed that they remain separate by an act of His indomitable power.
Related to this objection is another: how can the Body of Christ be in more than one place at a time? Would not Christ be impossibly multiplied in the many hosts?
In response: Only the accidents of bread and wine are divided up and distributed, and only the accidents can perish with time, as they do in the stomach of the recipient; the glorified Savior in Heaven, without suffering division or change, makes Himself wholly present in the Eucharist, which is truly one because its substance is truly one. St. Paul’s teaching — “The bread which we break, is it not a sharing in the Body of Christ? Because there is one bread, we who are many are one body, for we all partake of the one bread” (1 Cor. 10:16–17) — shows that one and the same Bread of Life, Jesus Himself (Jn. 6:35), is received by Christians under the appearances of that physical bread that can be broken up and given out. Though the comparison limps, even a mere man can be present at the same time in different places according to different modes: on a telephone conference call, a person is present to himself in one way and present to the others in another way, without ceasing to be the same man. In the Holy Eucharist, our Lord is present in a sacramental mode that permits of multipresence or multilocation.
Finally, some people think that the doctrine of transubstantiation is made untenable by “modern science.” The empirical sciences of recent centuries, however, have done no more than provide a vast amount of detailed information about the same world in which the ancients and medievals lived, the same world all of us live in and experience. There can never be any reasonable dispute about the normal sequence of events and the ordinary constitution of substances in the natural world. Just as the believer who eats the host tastes bread but knows by faith that he receives Jesus Christ, chemical analysis performed on a consecrated host (God forbid) would obviously indicate the accidental features of bread — just as the believer has always known. Neither the five senses of man nor the most advanced instruments of empirical science can reach into the inward substance of things; all they can know and register are the accidents, the appearances, the qualities and quantities, which, in the Eucharist, remain what they were before transubstantiation. The hostility that a modern empiricist might aim at the Eucharist is rooted in a prior axiomatic rejection of the existence of God or of the very possibility of miracles — i.e., events outside the ordinary “law-abiding” course of nature. These are errors to be engaged on a larger battlefield. Once the existence of God and the infinite perfections of His nature are demonstrated, it becomes impossible to deny the possibility of miracles, since the God who creates and sustains all things can do as He wishes with them, and because Jesus Christ is true God, it immediately follows that He can perform the miracle of transubstantiation by the infinite power of His divinity, a power to which the priest is given special access through his sacramental conformity to Christ the High Priest.
The recent Pew Research indicating a massive collapse among Catholics of faith in the Real Presence, which has been greeted either with crickets or with impressive denials from mainstream spokesmen (as when Bishop Barron flatly denied that the Novus Ordo has anything to do with it), surely tells us at least two things: first, the way in which most Catholics are worshiping is not helping them to perceive the dogmatic truths that the Church confesses, and second, all Catholics — regardless of how well or poorly our liturgies portray the mysteries of the faith — need to do more than go to church once a week if we want to know, love, and live our holy religion. Study is a part of this, and St. Thomas Aquinas is our trustworthy guide.
[i] An idiom like “Will we ever see justice?” means: Will we see the just thing done in this situation?
[ii] There are also two levels of substance. Primary substance is what we have been speaking of, the individual existing thing, this particular man or horse or tree. Secondary substance refers to the genus or species of an individual. “Animal” or “plant” may be called substance, but since there are only individual animals and plants in the world, substance most properly refers to actually existing things rather than things’ species or genera.
[iii] The expression “It doesn’t matter one iota” is a rationalist snub against the theological precision of our forefathers. One iota makes all the difference between Christianity and the dressed-up paganism of Arius.
[iv] See Lumen Gentium 11, Catechism of the Catholic Church 1324. That this adoration and vigilance have often been lacking, especially in recent decades, can hardly be blamed on official teaching. It results more from the decay in authority, the lack of effective discipline, and the gradual loss of a sense of Tradition among the faithful, as documented in Romano Amerio’s Iota Unum.
[v] See, inter alia, Jn. 6:48–60; Mt. 26:26–28, Mk. 14:22–24, Lk. 22:19–20; 1 Cor. 10:16–17, 11:23–29.
[vi] They see their linguistic reserve as a great virtue, of course, but this is no place to enter into a debate about why they are mistaken.
[vii] While bread is not a substance produced by nature, but rather a mixture of natural ingredients brought together by man and subjected to heating, the end result is not a mere conglomeration of ingredients, unless the baking has been quite unsuccessful; it is a consistently recognizable something to which we have no difficulty assigning a single name.
[viii] Inseparable now that Christ is risen and death holds no dominion over Him. The humanity we receive in the Eucharist is risen, glorified, whole, and imperishable. When Jesus first celebrated the Eucharist on Holy Thursday, the humanity received by the disciples was passible (able to suffer). St. Thomas goes so far as to say that if the Eucharist had been offered during the interval between Christ’s death and resurrection, the host would have contained the Body with the Divinity but without the Blood or the Soul, and the chalice would have contained the Blood with the Divinity but without the Body or the Soul. All this is simply the rigorous application of the principle that the Eucharist contains the substance of Christ as He is.
[ix] Since the Council, the aberration of Communion under both kinds has spread widely in the Latin Church. It goes beyond the scope of this article to defend the tradition and to critique this piece of antiquarianism.
Dr. Peter Kwasniewski is a graduate of Thomas Aquinas College and The Catholic University of America who taught at the International Theological Institute in Austria, the Franciscan University of Steubenville’s Austria Program, and Wyoming Catholic College, which he helped establish in 2006. Today he is a full-time writer and speaker on traditional Catholicism whose work appears online at, among others, OnePeterFive, New Liturgical Movement, LifeSiteNews, The Remnant, and Catholic Family News. He has published eighteen books, including Reclaiming Our Roman Catholic Birthright: The Genius and Timeliness of the Traditional Latin Mass (Angelico, 2020), The Ecstasy of Love in the Thought of Thomas Aquinas (Emmaus, 2021), and Are Canonizations Infallible? Revisiting a Disputed Question (Arouca, 2021). His work has been translated into at least eighteen languages. Visit his website at www.peterkwasniewski.com.