My Introduction
Dominic Legge’s book, The Trinitarian Christology of St. Thomas Aquinas, seeks to affirm one simple but critical statement: “Aquinas’s Christology is Trinitarian.”
The significance of this statement is threefold:
- For apologetic reasons – to defend Aquinas against those who, like Rahner and Balthasar, accused Aquinas of divorcing Christology from the Trinity;
- For Thomistic reasons – to present Aquinas’ unity of thought and the intelligible order he discerns in the whole dispensation of salvation history (as it emerges from the Trinity and leads us back to the Trinity);
- For salvific reasons – to allow Aquinas to “draw us into the search for the highest truths – and into the delightful contemplation of the divine mystery – that animated his own life” (7).
I highly recommend you read this book yourself. My “summary” is very brief, is based mostly on my 3-page book review that I did for Fr. White’s Trinity class at the Angelicum (click here for that), misses a lot of importance distinctions that Legge makes throughout this great book.
Part I: The Trinity and the Dispensation of Salvation
Part I establishes the foundation for a Trinitarian Christology by looking at Aquinas’s writings on the relation between eternal processions and divine missions.
Eternal processions describe the ad intra life of God.
The Son proceeds from the Father by way of the intellect as the Word (cf. John 1:1-2, 8:42) and the Holy Spirit proceeds from the Father and the Son by way of the will as the Love between the Father and the Son (cf. John 14:25-26, 15:26, 16:7). For Aquinas, eternal processions are “the ultimate basis for the distinction of the persons within the Trinity” (12).
Divine missions describe the ad extra life of God.
The Son’s visible mission in the incarnation and the Holy Spirit’s invisible mission to Christ’s humanity and visible mission to the apostles at Pentecost are three important examples of divine missions among many others. For Aquinas, divine missions, which can be (1) visible (e.g., the incarnation) or (2) invisible (e.g., the indwelling of the divine persons in a soul by grace cf. Gal 4:6), “include the eternal procession, and adds something, namely, a temporal effect” (STh I. q. 43, a. 2 ad 3). In addition, in speaking about the purpose of the two different types of missions, Aquinas states that “the visible missions are ultimately ordered to the invisible missions” (Ecce rex tuus) whereby the divine persons may be in us (through sanctifying grace), conform us to their processions & missions (through the gifts of wisdom and love), and lead us back to the Father (cf. Rom. 8:15).
Eternal processions are the cause and ratio of divine missions.
Based upon the principle that “the first procession is the cause and ratio of every subsequent procession” (I Sent. prol.), Aquinas presents the eternal processions to be the cause and ratio (i.e. reason, meaning, explanation) of the divine missions. In a way, “the eternal processions in God are ‘extended’ into time in the divine missions” (5). As a result, the eternal processions are the cause and ratio of the entire exitus (of creatures from God) and reditus of salvation history (of creatures back to God). Thus, “the visible mission of the Son in the incarnation – accompanied by the missions of the Holy Spirit to Christ and, at Pentecost, to the Church – are the means, “the way,” by which all of creation is brought back to the Triune God as its final end” (13).
Part II: Jesus Christ, the Word of the Father Sent in the Flesh
Legge narrows his focus in Part II to explain why, for Aquinas, the eternal processions are the cause and ratio of the central event in salvation history – the visible mission of the Son in the incarnation. He structures his discourse around three proper names (Word, Son, Image) and one proper designation (Author of Sanctification) for the second person of the Trinity – thereby manifesting the “deep intelligibility of this mystery” (62) and the supreme fittingness of why the Word became incarnate.
1st: Word.
Since the second person of the Trinity proceeded from the Father by way of intellect as “both begotten wisdom and the divine exemplar of all things,” (71) as is thereby properly named the Word (i.e., “since a word represents a conception of understanding in the intellect and “proceeds as the fruit of understanding” (66), it was fitting that God would manifest this eternal procession through the visible mission of the incarnation in order to recreate all things according to the same eternal wisdom and divine exemplar of the Word (cf. John 1:14; 1 Cor. 1:24; Wis. 9:19).
Also, since “a word manifests its speaker,” it is proper for the Word to manifest the Speaker – the Father (cf. John 17:6), and thereby lead us to our final end, “which is nothing other than the perfect knowledge of the Holy Trinity in the beatifying vision of God” (78).
2nd: Son.
Since the second person of the Trinity proceeded from the Father as only begotten and consubstantial, “having the same nature and knowledge as the Father” (Aquinas, In Ioan. c. 1, lect. 11 (nos. 217-218), qtd in Legge, 85), as is thereby properly named the Son, it was fitting that God would reveal this eternal procession through the visible mission of the incarnation so that we could participate in his sonship by “adoption,” sharing in his nature and knowledge of the Father, and return with him to the Father to enjoy his inheritance in heaven (cf. Ps. 15:5; Rom. 8:17).
3rd: Image.
Since the second person of the Trinity proceeded from the Father as the perfect “image of the invisible God” (Col. 1:15), as is thereby properly named Image, it was fitting that God would reveal this eternal procession through the visible mission of the incarnation to restore and perfect this image in us (cf. Rom. 8:29; 1 Cor. 15:49).
4th: Author of Sanctification.
Since the second person of the Trinity, who is, with the Father, “a principle and giver of the Holy Spirit” (97), it was fitting that God would extend this eternal procession of the Holy Spirit into time by giving the Holy Spirit, “who is himself the Gift of sanctification in person” (Ibid) for the forgiveness of sins that man needed (cf. John 20:22-3). Therefore, the proper designation of the second person of the Trinity as Author of Sanctification (cf. Heb. 2:10).
The hypostatic union
With these four titles in mind, Legge ends Part II with Aquinas’s insights into the Trinitarian dimension of the hypostatic union in order to make one clear distinction. Although “the whole Trinity, by virtue of the one nature and one power of all three divine persons, is a principle of the Son’s assumption of a human nature” (104), the second person of the Trinity, and he alone, as a terminus “according to his personal esse” (128), is the incarnate Son. This is an important distinction because it links all of Christ’s activity in his human nature with his unique procession as the Son (in a filial mode) and thereby gives metaphysical depth to Aquinas’s idea that the incarnation truly is the visible mission of the Son in all its Trinitarian scope (cf. John 5:19, 17:4).
Part III: Christ and the Holy Spirit
Part III examines the relation between Christ and the Holy Spirit in order to give a complete picture of how both eternal processions are the cause and ratio of all the divine missions. For the purpose of this summary, two brief points can be made.
First, since “the Word (with the Father) breathes forth the Holy Spirit from all eternity [in the divine processions], so the Word made flesh (who is from the Father) breathes forth the Holy Spirit in time” (6) in the divine missions. Therefore, when “the Word became flesh” (John 1:14) in the visible mission of the incarnation, the Word (with the Father) breathed forth the Holy Spirit in an invisible mission to Christ’s assumed human nature, elevating and perfecting Christ’s human nature through “habitual grace” (which is is the created effect of the indwelling of the Holy Spirit) to accomplish the divine mission he had been given by the Father (cf. Luke 4:18; Acts 10:38).
Second, since the divine missions are only complete in our return back to God, the missions of the Son and the Holy Spirit are also ordered towards leading us back to the Father according to the “very shape and internal structure” (234) of their eternal processions of knowledge (Son) and love (Holy Spirit) (cf. Tit. 3:5-6). These missions, although distinct and in proper order according to the pure order of Trinitarian processions, are always “simultaneous, inseparable, and coordinated” (150). Through our reception of the “missions of the Son and Spirit in sanctifying grace” (14), we are “assimilated to a likeness of the divine persons” (39), made capable of knowing and loving God, and ultimately brought through Christ and in the Holy Spirit to “the glory of heaven, in which [we] are united directly to the Father, Son, and Holy Spirit in the beatifying vision of God” (14).
Going Deeper:
I highly recommend that you watch the following two videos – multiple times if need be! – and follow the Thomistic Institute on YouTube!
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