In the early days of the Church, the Fathers knew well the importance of fine care in the choice of language and terminology. Perhaps nothing made the statement more clearly on the difference an iota (or a jot or a tittle) could make than the early Arian and Semi-Arian controversies of the fourth and fifth centuries, when the immense metaphysical gulf between homoousios and homoiousios threatened to capsize the barque of Peter. The question facing them, one that still plagues us today, is how to put the ineffable mysteries of God into language that communicates the Truth. While morphology took center stage in the earliest controversies, semiology became the focus during later debates—in particular, how we speak about Christ and His Divinity and what can be predicated to His two natures.
Primarily, when we speak about Christ’s two natures and what can be predicated to each of them, we are referring to the theological concept “communication of idioms” or “communication of properties.” Secondarily, we can include implications drawn from this communication. The teaching of the Church on these matters was established initially at the Council of Ephesus[i] and later clarified and confirmed at the Council of Chalcedon. The majority of these pronouncements addressed what has come to be known as the Hypostatic Union.[ii] Aside from the basic teaching about the dual natures of Christ, the Fathers of the council definitively stated that because one Person subsists in two natures, activities and properties that could be predicated of either nature could rightly be predicated of the Person. Thus, the council defended the use of the title Theotokos, the God-Bearer, for the Blessed Mother, stressing that Mary was the mother of the Person of Christ, Who is God.[iii]
The understanding of how to put these realities into words developed over centuries. According to Ocáriz et al, the first person to set down rules on such Christological language was Leontius of Byzantium. However, St. Thomas is known as the primary source for the main rules on the “exchange of properties” (yet another phrase for the same concept).[iv] This general principle has been formulated in numerous ways. Kenneth Baker writes “that human things can be asserted to the Son of God and Divine things to the Son of Man.”[v] While this description is certainly true, it does not aspire to the level of precision detailed by St. Thomas. The argument, as presented by the council Fathers, is essentially that properties and activities are typically ascribed to a Person rather than to his or her nature. In this sense, one can say that God, in the Person of the Son, was born of a Virgin and was crucified.
Thus, whatever can be said of one of the natures of Christ can be attributed to the Person of Christ. The key in speaking of Christ, then, is precision in predication of actions and properties to natures or to the Person. Anthony Maas suggests three considerations in applying this principle.[vi] This paper will discuss these three considerations in applying the principle of communication of idioms.[vii]
The first consideration is that those statements interchanging Divine and human properties are generally correct, so long as both subject and predicate are stated in concrete terms.[viii] In the most basic sense, we can say that God is man, if we mean this statement in the sense that God assumed a human nature and a body. St. Thomas points out, though, that the Manicheans used this statement in an elliptical way, to mean that God was a fictitious man rather than man in the flesh (III, 16, 1). He notes that both subject and predicate refer to the suppositum, and in this sense, it is true that God is man, and likewise that man is God. In this category, too, fall all of those utterances that pertain to the Person of Christ in His hypostasis or suppositum. When a property belongs to a nature, it can be attributed to the Person, so while Christ suffered in His human nature, His Person suffered. In this sense, God suffered. Inversely, as Ocáriz et al point out, we can say that the Son of David is almighty.[ix]
When we speak of the Person of God, we can speak objectively about a concrete entity. However, as Maas notes, we have to do so with caution. Some utterances, such as “man became God,” suggest that man subsisted in human nature prior to Christ’s assumption of that nature, which is false.[x] In addition, when a concrete term is used with reduplication, for example in “Christ as Man is God,” the emphasis is on the nature rather than the suppositum, as St. Thomas notes, so the clause in this instance is taken to be false (III, 16, 11). In such cases, one must take care not to attribute to one nature that which belongs to the other. If we say that “Christ as Man is a creature” (III, 16, 8), we are referring to His created human nature, but if we say “Christ as Man is God,” we are attributing divinity to His human nature. On the other hand, when demonstrative constructions are used, we are speaking clearly of the suppositum rather than the nature. To say “This Man, Christ…” is to point at the eternal Person of the Son of God since He subsisted first in His Divine nature. Anything, then, predicated to suppositum must take this fact into consideration. If we say, “This Man, Christ, came to be,” we can only say so truthfully with qualification—that He came to be in His humanity (III, 16, 9).
Maas’ second consideration addresses the use of abstract terms, which generally respect one or the other nature. Statements concerning Divine and human properties of Christ are, in general, incorrect if either subject, predicate, or both are abstract.[xi] For example, we cannot say that Christ’s humanity is omnipotence or that His Divinity was humanized. However, some exchange of abstract is acceptable, and we can predicate abstract names of the Divine nature of concrete names of the human nature: for example, this Man, Christ, is the Omnipotence.[xii] There is less danger when we begin talking specifically about the Second Person of the Trinity since abstract properties of either nature can be attributed to Him as the Person of the Son of God. Yet again, this does not mean that the abstract properties of one nature can be attributed to the other. We cannot, without error, say that “The Word is the humanity” or “the Word is the soul or the body of Christ.”[xiii]
St. Thomas addresses the use of abstractions specifically in part III, question 16, articles 3 and 5. In article 3, he discusses the predication of the terms God and Lord denominatively. While we call the Son of God Lord, we cannot call Him “lordly Man” since to do so would derogate the truth about the union of natures in the Person of Christ. In article 5, he writes of the predication of properties of the human nature of the Divine nature, which likewise is errant. So while we can attribute human properties to the Person of Christ, we cannot attribute them to the Godhead. We can say that Christ suffered and died. We cannot say that the Godhead suffered and died or suggest that the Godhead is passible or corruptible.
The third consideration is that statements must be used with care to avoid destroying the properties of one or the other nature.[xiv] Such statements would include those that speak to Christ’s humanity in such a way that His Divinity is put into question. For example, one can say the God was made man without inferring anything about Christ contrary to either nature. However, if the terms are traded and one says “man was made God,” an incorrect impression is given that man subsisted in his human nature prior to being assumed by the Second Person of the Trinity (III, 16, 7). In the same sense it would be incorrect to say that “Christ began to be” without qualifying the statement further: for example, “this Man, Christ, began to be in His humanity” (III, 16, 9).
Maas notes that negative sentences can sometimes be used in such a way that one or the other nature is denied. While it might be true in one sense that the Son of God did not die (in His Divine nature), one cannot say “the Son of God did not die” without implicitly denying His human nature. One might also (errantly) speak restrictively in a way that denies one or the other nature: for example, that Christ was not passible or that Christ was a creature (III, 16, 8). Again, while these statements can be true of one or other of the natures of Christ, they cannot be said to be true of the Person of Christ without denial of either His Divinity or His humanity.
Some theologians say that heresy is the emphasis of one truth to the exclusion or detriment of others. The Arians, not wanting to make Christ the equal of God, emphasized His humanity to the detriment of His Divinity. The Nestorians, not wishing to reduce His Divinity, weakened the union of natures in the Person of the Son. Still later, the Monophysites emphasized the union to such a degree as to destroy the distinction between the two natures. Along the way, simple lack of precision played a part in advancing error (for example, when Euthyches and his adherents misinterpreted St. Cyril’s writings about the union of natures in the Person[xv]). For this reason, theologians must take great pains for clarity in their use of Christological language, particularly in the area of communication of idioms. As the author of Hebrews wrote, “Jesus Christ is the same yesterday and today and for ever” (13:8). Yet Jesus was born of a virgin, suffered, and died. We hold many truths in tension, and so our words we must choose with clear intention.
Aquinas, T. (2000). Summa Theologica, Tertia Pars. Retrieved September 18, 2010, from New Advent: http://www.newadvent.org/summa/4.htm
Baker, K. (1983). Fundamentals of Catholicism (Vol. 2). San Francisco: Ignatius Press.
Maas, A. (1908). Communicatio Idiomatum. Retrieved November 7, 2010, from New Catholic Encyclopedia: http://www.newadvent.org/cathen/04169a.htm
Mosey, R. D. (2006). "Patristics: Lecture 3." International Catholic University. Catholic Educational Television, Inc.
Ocáriz, F., Mateo-Seco, L. F., & Riestra, J. A. (2008). The Mystery of Jesus Christ. Dublin: Four Courts Press.
Ott, L. (1974). Fundamentals of Catholic Dogma. Rockford, Illinois: Tan Books and Publishers.
i. Ludwig Ott, (1974), Fundamentals of Catholic Dogma, (Rockford, Illinois: Tan Books and Publishers), p. 144.
ii. Douglas Mosey, (2006), “Patristics: Lecture 3,” International Catholic University. Catholic Educational Television, Inc.
iv. F. Ocáriz, L. F. Mateo-Seco, & J. A. Riestra, (2008), The Mystery of Jesus Christ, (Dublin: Four Courts Press), p.135.
v. Kenneth Baker, (1983), Fundamentals of Catholicism (Vol. 2), (San Francisco: Ignatius Press), p. 241.
vi. Anthony Maas, (1908), Communicatio Idiomatum, Retrieved November 7, 2010, from New Catholic Encyclopedia: http://www.newadvent.org/cathen/04169a.htm.
vii. Ocáriz et al have a more complex breakdown that also treats the subject well, but the author has chosen Maas’ more basic approach for simplicity’s sake.
viii. Maas, http://www.newadvent.org/cathen/04169a.htm.
ix. Ocáriz, p. 134.
x. Maas, http://www.newadvent.org/cathen/04169a.htm.
xi. Maas, http://www.newadvent.org/cathen/04169a.htm.
xii. Ocáriz, p. 135.
xiii. Maas, http://www.newadvent.org/cathen/04169a.htm.
xv. Ott, p. 146.