In the study of Christology, St. Thomas’ use of Aristotelian natural science helps to avoid two extremes: 1) the neo-modernist “Christology from below” with its Nestorian and Arian tendencies and 2) the Monophysitism implicit in any theology which denigrates our Lord’s Sacred Humanity. The key concept in Aristotelian philosophy ad rem to this subject is the “analogy of being.”
Central to a proper notion of analogy is the Aristotelian notion of which science is the ultimate science, the one which coordinates all the others. Such a science would render possible epistemological transitions from one field of knowledge to another without doing violence to the principles proper to each. Included in these diverse fields would be those treating realities that rise above the natural sciences (in the sense of “sciences which rely only upon natural reason”). That ultimate science is metaphysics, or ontology: “Such a First Science preserves the autonomy of the special sciences but coordinates them by comparing their basic principles and concepts according to their similarities and differences (analogy). This ultimate science came to be called metaphysics (after physics or natural science).”
In applying the concept of analogy to Christology, we can divide our subject matter into (I) God considered in His essense and attributes, (II) the Trinity and the Logos asarkos, and finally, (III) the Logos ensarkos.
I. Speaking of the “violent anti-intellectualism” of the Protestant Reformation, Mortimer Adler faulted Protestant “Theology” for its failure to grasp the analogy of being. Exemplifying the foundational importance of analogy to the vocabulary by which we speak of God, he pointed out the failure of modern Protestantism to deal with the challenge posed in Ludwig Fauerbach’s The Essence of Christianity: “[Fauerbach] noted that the attributes of God and of man appear to be the same. We say that God lives and that man lives, that God knows and that man knows, that God wills and that man wills, that God loves and that man loves. Feuerbach then pointed out quite rightly that when two objects have the same attributes, they must be identical. God and man have the same attributes, hence they are identical. …
“The remarkable fact is that six generations of German Protestant theologians from Schleiemacher to Karl Barth and down to the present day, all knew that this was a deathblow to Christianity. Yet none was able to answer Feuerbach by correcting the basic error he made. His basic error was his failure to see that while God and man have the same attributes, ‘living,’ ‘knowing,’ ‘willing,’ and ‘loving’ when said of God and man are said analogously, not univocally…”
What Adler applies to the acts of God, we may apply to His essence and attributes. God is. I (Brother André Marie) am. But while I am, I may never say of myself “I am who am.” My being is derived, contingent, utterly dependant on the only Being whose essence to exist. That being, and He alone, may say “I am who am” because he is the necessary being, the being who is the fullness of being.
So, too, when I am merciful, or just, or provident to those depending on me, etc., I am all those things in a finite, derived sense and secundum quid. God is all those in an infinite, absolute sense, and simpliciter.
To speak at all intelligently about God, and especially to deal with the perverse objections thrown out by modernists and secularists such as Fauerbach (e.g., when they mock the anthropomorphisms in Holy Scripture), we must resort to the concept of analogy. That we may do so – and, further, that we may cite such an elevated philosophical insight in the writings of Medieval theologians – will go a long way in disabusing the proud modern mind of its anti-Catholic prejudices.
II. Regarding the doctrine of the Trinity and, therefore, of the Logos asarkos (which must be touched upon before any Christology can be formulated), we use analogy in the term by which we distinguish Father, Son, and Holy Ghost: Person. “[M]etaphysics helps us to apply the relational implications of the analogous term ‘person’ to God. To be a human person is not only to exist but also to be capable of personal relations, since a person is intelligent and capable of love and what any person chiefly knows and loves are other persons with whom that person enters into relationship.”
Thus the data supplied us by revelation can be clearly and intelligently presented in the face of the sophisms of a Fauerbach. For instance, in the prologue of St. John’s Gospel, the Logos is said to be “with God” and “God.” He shares a “what-ness” with the Father, but has a “who-ness” that is distinct. All throughout the Prologue, and all throughout St. John’s Gospel, we read constant references to the “oneness” that the Son and Father have, yet with something distinguishing them so that they may be seen “in relation” to each other. What distinguishes them is personhood.
What we say of the analogous use of the term “person” may also be said of the analogous use of the names of each of the Three: “The term ‘father’ with respect to God is taken from human relationships, which are created. It cannot be applied to God without some change in meaning to befit an infinite being.”  “[‘Father’] is generally ascribed to God in the Old Testament to manifest his transcendence and immanence to creation… The New Testament adds a new dimension [to the analogy] – a Trinitarian dimension.”
This seems to be what St. Paul was getting at when he said, “I bow my knees to the Father of our Lord Jesus Christ, of whom all paternity in heaven and earth is named.” The primary analogue is God’s Fatherhood; the secondary is created fatherhood.
In analogy, something is the same and something is different. What is it that is the same and what is different in the analogous use of the word “father”? “St. Thomas is very exact: ‘The name of Father signifies directly a relation and, obliquely, the essence with which it is identical.’ The term ‘Father’ within the Trinity refers to the difference in ‘relation of origin.’ “ Therefore, the word must be mentally purged of any notions of precedence in time, of bodily generation, of superiority to a subordinate son, etc., all of which are present in human fatherhood: all of these notes are different. What is the same is the concept of relatio originis.
If this is true of “Father,” so also, the Trinitarian correlative, “Son” must be analogously applied to the Logos.
Stealthily citing the Augustinian Rule, Father Ashley notes the analogous concept of “community” in God: “When we know and love another intimately we enter into community with that other person, giving ourselves to that other and become, as it were, ‘of one heart and one mind.’… Hence it is not contradictory to see that in God who is supreme Intelligence and Love this self-giving of the Father eternally pours out into the Son, and between the Son and the Father there is a total equality of life, knowledge, and love in the Holy Spirit.” Thus, in the community of the Blessed Trinity, we have the primary analogue for the community of the Church and of all human societies, beginning with the family.
An attentive reading of Father Ashley’s text will show that this analogous community life in the Trinity goes beyond the processions and includes the notion of perichorisis, the mutual indwelling of all three Persons. Without perichorisis, the Holy Ghost would not be able to “share” anything of His Person with the Father; He would only be the recipient of the active spiration of the Father and the Son.
Citing Karl Rahner in a rare burst of pithy orthodoxy, Father Ashley points out that the economic Trinity reveals the ontological Trinity, i.e., the Trinitarian works (including the missions) ad extra in time reveal the Trinitarian processions in eternity: “as the Father is manifest in Creation, the Son is manifest in the historic Incarnation, and the Holy Spirit is manifest in the historic work of the Church. Thus world history is a manifestation of the eternal outpouring of life and love within God.” In the context, this was Father Ashley’s ironic twist on the historicist idea of history as the science which coordinates all other sciences. For our purposes, Rahner’s insight provides a useful segue into considerations of the Logos ensarkos, and therefore of Christology proper.
III. In the philosophical consideration of the human person, we normally speak of nature as that which “is had” and person as that which “has” (persona habet, natura habetur). In natural philosophy, there is a one-to-one correspondence in these concepts, so that one person “has” only one nature and one nature “is had” by only one person. However, even in psychology, there is a real distinction between the two. Only in God do essence and existence strictly coincide. How, then, do we understand Christ to be a divine person with two natures, as we must believe on the authority of God revealing through the Council of Ephesus? By analogy:
“Since for this necessary First Cause or God existence and essence (nature) must be identical (otherwise it would not necessarily exist), essence (nature) and existence in the material and spiritual creatures that are God’s effects, must be really distinct. Thus Jesus’ human nature was really distinct from his personhood, since by “person” we mean the very existence of a being who has spiritual intelligence and free will. The metaphysical solution is to be found in the analogical concept of ‘person’ as one existent with two essences or natures, total divinity and total humanity.” Here, person has been purged of the notion of a strict one-to-one correspondence with nature (the “something different”), while it still corresponds to existence, as in human psychology (the “something the same”).
Father Ashley seems also to apply analogy to the communicatio idiomatum, the communication of idioms predicated of one nature of Christ to the other due to their ineffable union in one Hypostasis: “Thus it is literally true that God suffers as we suffer, although he suffers not in his divine nature but in his human nature, analogous to the fact that when I have a tooth ache it is in my body that I suffer not in my intelligence, since I may be quite confident that the dentist will soon fix that tooth and take away the pain; yet it is truly I who suffer that excruciating pain.”
These are only a few brief considerations of the utility of the Aristoteleo-Thomistic concept of analogy in Christology.
 Mullady, O.P., S.T.D., Fr. Brian, Man’s Desire for God (Bloomington: 1stBooks, 2003), 40.
 Ibid, 43.
 Ephesians 3:14-15.
 Mullady, 44.