¹ The typical example Saint Thomas gives is of heat. What has the maximum of heat is the cause of all heat. See, for instance, Summa Theologiae, 4 vols. (Ottawa: Commissio Piana, 1953), (hereafter ST), III, q. 9, a. 2, co.: ‘What is in potency is reduced to act by that which is in act, for it is necessary that what makes other things to be hot itself be hot’. Unless otherwise noted, all translations from the Latin and French are my own. On the causality of the maximum see V. de Couesnongle, ‘La causalité du Maximum: L’utilisation par Saint Thomas d’un passage d’Aristote’, Revue des Sciences Philosophiques et Théologiques, 38 (1954), 433–44 and ‘La causalité du maximum: Pourquoi Saint Thomas a-t-il mal cité Aristote?’ Revue des Sciences Philosophiques et Théologiques, 38 (1954), 658–80.

² ST III, q. 8, a. 6, co.

³ Arguably, this is the chief aspect of headship. See ST III, q. 8, a. 1, co. St. Thomas names three respects in which the headship of Christ is similar to the natural head: order, perfection, and power. While Christ is head in all three ways, the first and second aspects clearly correspond to the grace of union and Christ’s singular grace, respectively. Thus, it is primarily in relation to the third aspect, the power of causing sense and motion in the members of the body, that Christ is called head – i.e., inasmuch as he bestows grace on all the members.

⁴ Saint Thomas is not unique in seeing the angels as subjected to Christ’s headship. The teaching has its roots in Scripture (Eph. 2:20–22; Col. 2:10) and in the authority of Dionysius (Celestial Hierarchy, ch. 7). Thomas argues for the unity of angels and human beings on the basis of their common supernatural end. See ST III, q. 8, a. 4, ad 2. Since Christ is not only head of wayfarers but also of comprehensors, it follows that he is the head of the blessed angels – for he has the fullness of grace and glory.

⁵ Or, as Karl Barth might put it, through the Logos incarnandus – i.e., the Word about to be Incarnate. See Church Dogmatics IV/2. Of course, the notable difference between the Old Testament saints and the blessed angels is that the former existed after the fall, whereas the latter would not have been redeemed from a fallen state, but would have moved from a state of original grace to glory.

⁶ Cf., ST III, q. 1, a. 3: ‘For those things which arise from the will of God alone, beyond the due of any creature, cannot be known by us unless it be handed down in Sacred Scripture through which the divine will is known. Wherefore, since in Sacred Scripture the reason [for the Incarnation] is taken from the sin of the first man, it is more fittingly (convenientius) said that the Incarnation is ordered by God in remedy for sin, so that, if sin had not existed, the Incarnation would not have occurred. Yet, the power of God is not restricted to this, for, even if sin had not existed, God could still have become incarnate’. While Thomas clearly recognizes that things could have been otherwise (i.e., God could have become Incarnate even without sin), nevertheless, he seems committed to saying no more than what is given to us explicitly in Sacred Scripture.

⁷ According to St. Thomas’s Compendium theologiae Bk I, ch. 2, two truths in particular fall under this category: the divinity of the Trinity and the humanity of Christ. It is helpful to compare the use of Thomas’s principle of the causality of the maximum in his account of Christ’s perfection with his use of the same principle in his demonstration of God’s existence in the fourth way (see ST I, q. 2, a. 3, co.).

⁸ In other words, the ambiguity in Thomas’s account is a concrete example of his theological method as spelled out in ST I, q. 1, a. 8, ad 2.

⁹ ST III, q. 8, a. 1; a. 4, co. This is in distinct contrast to the Franciscan idea of Christ as head primarily according to his conformity to us.

¹⁰ See ST III, q. 7, a. 9, co.

¹¹ Saint Thomas’s enumeration and explanation of these three types of grace can be understood as an explication of John 1:14 and 16, which speak of the Word becoming flesh (order: grace of union), full of grace and truth (perfection: individual grace), from whose fullness we have all received (power: capital grace). See Franklin T. Harkins, ‘Christ’s Perfect Grace and Beatific Knowledge in Aquinas: The Influence of John Damascene’, in Reading the Church Fathers with St. Thomas Aquinas: Historical and Systematical Perspectives, ed. by Piotr Roszak and Jorgen Vijgen (Turnhout: Brepols, 2021), pp. 339–72. Harkins does an excellent job showing how Thomas’s doctrine of Christ’s grace and beatific knowledge is grounded in a careful reading of John 1:14 and 16.

¹² This is based on yet another metaphysical principle pertaining to a thing’s nearness to its causal source, which is cited in other passages. See III, q. 7, a. 9, co.: ‘The nearer a thing is to the flowing cause, the more perfectly it participates in its effects’.

¹³ See ST III, q. 7, a. 9, co. In this regard, Saint Thomas will also say that Christ’s grace is infinite, see ST III, q. 7, a. 11, co. See also, ST III, q. 7, a. 11, ad 3.

¹⁴ ST III, q. 8, a. 1, ad 1 distinguishes between the authoritative and instrumental communication of grace. Only the latter belongs to Christ as human, which nevertheless does not exclude Christ’s humanity as an efficient cause of grace. This distinguishes Christ from others who also communicate grace instrumentally.

¹⁵ See for example Alexander of Hales, Doctoris Irrefragabilis Alexandri de Hales Ordinis Minorum Summa Theologica, 4 vols (Quaracchi: Collegium S. Bonaventurae, 1924–48), Vol III, In1, Tr3, Q1, Ti1 (p. 141): ‘It must be said that in Christ, according as he is man, there is grace according as he is head of the Church. In order to understand this, it must be known that the influence of grace is from God either without a medium or through a medium. Without a medium Christ, as God, is immediately the giver of grace by authority and by the proper reason of efficient causality […] Through a medium Christ, according as he is man, in many ways: for he is a medium by way of faith, by way of merit, by way of desire or prayer, and by way of disposition’. The Halensist proceeds to describe the various ways in which Christ, as human, acts as a medium of grace. Notably, none of these is by way of efficient cause. Rather, in each case, Christ disposes God (through prayer, merit, etc.) to give grace to believers through the Holy Spirit. For the Halensist, grace is communicated only through the Holy Spirit. This is true of Christ’s created grace, as well as the grace of others. In this way, the relationship of the Holy Spirit to Christ is in many ways parallel to the relationship between the Holy Spirit and other pure human beings. The created grace of union, ‘not only disposes [the human nature of Christ] to knowledge and love of God, but even to the personal unity with God’, Vol III, In1, Tr3, Q1, Ti2 (p. 145). For a text which provides a similar distinction in the two ways that Christ is the source of grace, see Bonaventure, see In III Sent., dist. 13, a. 2, q. 1, resp. (Opera omnia, Quaracchi, t. 3, 1887, pp. 284–85): ‘But the properties, namely of influencing sense and motion, belong to him by reason of the divinity and by reason of the humanity. For to communicate (influere) the sense and motion of grace belongs to him in two ways: either through mode of one preparing (praeparantis), or through the mode of one imparting (impartientis). If through the mode of one preparing, then it belongs to Christ by reason of his own human nature, in which he suffered for us and by suffering satisfied and removed the enmity and disposed [us] for the reception of perfect grace. If through the mode of one imparting or conferring, then it belongs to Christ by reason of the divine nature, who “alone is God, who illuminates pious minds,” it is he alone who baptizes interiorly, because “our mind is formed directly by Truth itself,” as Augustine often says. – Or to say the same thing in different words, to influence through the mode of meriting belongs to Christ the man; through mode of efficient cause, to Christ God; or to influence as to the remission of the punishment (poenae), to Christ the man, as to the remission of fault (culpae), to Christ God. And thus, influence in one way pertains to Christ according to the created nature, in another way according to the uncreated nature’.

¹⁶ On Christ’s humanity as the instrument of the divinity see Theophil Tschipke, L’humanité du Christ Comme Instrument de salut de la divinité, trans. by Philibert Secrétan (Fribourg: Academic Press Fribourg: 2003) and Gilles Emery, ‘Christ, le Mediateur’, in ‘Christus–Gottes schöpferisches Wort’: Feschrift für Christoph Kardinal Schönborn zum 65. Geburtstag eds. George Augustin, Marian Brun, Erwin Keller, Markus Schulze (Freiberg: Verlag Herder GmbH, 2010), pp. 337–55. We see at least the beginning of a shift in Albert, who explicitly denies that the grace of union is created and instead prioritizes the grace of headship first in his De incarnatione, tract. 5, q. 2, and later in his commentary on the Sentences. See Albert the Great, In III Sent., dist. 13, a. 2, sol. (ed. Borgnet, t. 28, 1894, p. 238a). Here, Albert’s account is a bit muddled (for he seems at times to speak as though Christ as human is the source of grace, at other times as if this is restricted solely to the divinity). But he tells us that the head assimilates members to itself ‘through something which it communicates, which is like a form’. He continues, ‘in this way [Christ] is the head of the blessed and of those existing in grace, to whom he flows something like (quasi) a similitude of his own life, both his motion and his sense, in gifts perfecting the intellect and affection (intellectum et affectum)’. The immediate context suggests that this is according to Christ’s human nature. For Albert, it is not so much his conformity to the members of the body that makes him, as human head, but rather the way in which he, through his humanity, conforms the members of the body to himself.

¹⁷ See ST I, q. 2, a. 3, co.: ‘[T]he maximum in a genus is the cause of all that belongs to that genus, as fire, which is the maximum of heat, is the cause of heat in all that is hot’.

¹⁸ The broader context is a treatment of Christ’s grace in terms of final, efficient, and formal cause. The treatment of the various luminary bodies arises with respect to efficient causality. This might lead some to think that the Halensist is attributing efficient causal power to Christ’s humanity itself. This is not the case, however. Due to the Halensian understanding of the uncreated grace of union, to speak of Christ’s grace in terms of efficient causality turns out to be more a statement of the action of the Holy Spirit (who communicates grace to Christ and to others) than that of Christ as human. Thus, to speak of Christ’s grace in terms of efficient causality, and therefore in terms of his headship, is to speak of his grace inasmuch as he is conformed to the members of the Church. See Summa fratris, Vol III, In1, Tr3, Q1, Ti2 (p. 150): ‘For the whole Trinity moves and rules the Church and infuses grace into her, by which she might sense through faith and be moved through charity [….] but according to the humanity, Christ is properly called head because he is related to the Church on account of his conformity to her through grace and nature’. Against an objection that the Holy Spirit is thus constituted as the head of the Church rather than Christ, the Halensist responds: ‘[A]lthough the influence to the Church of every sense and motion of spiritual grace is from [the Holy Spirit], nevertheless, it does not belong to him to be in conformity of nature with the Church, and, therefore, it is not fitting that he be head, properly, but commonly, or less properly’, (Summa fratris, Vol III, In1, Tr3, Q1, Ti2 (p. 151).

¹⁹ See In III Sent., dist. 13, q. 1, a. 2, qc. 1, co.

²⁰ See In III Sent., dist. 13, q. 1, a. 2, qc. 1, co.

²¹ Thomas Aquinas, Quaestiones disputatae de veritate, Leonine edn, Vol. 22, parts 1–3 (Rome: Editori di san Tommaso, 1970–76), (hereafter DV), q. 29, a. 5, co. The use of rational (rationales) rather than intellectual suggests that here Thomas is considering Christ’s headship with respect to humans alone.

²² See ST III, q. 7, a. 9, co. Emphasis added.

²³ ST III, q. 8, a. 6, co.

²⁴ For more on how these various principles (i.e., the causality of the maximum and the principle of propinquity) function in Thomas’s understanding of Christ’s perfection, see Joshua H. Lim, ‘The Principle of Perfection in Thirteenth-Century accounts of Christ’s Human Perfection’, The International Journal of Systematic Theology, 24 (2022), 352–79.

²⁵ For example, Eph 1:20–23; Col 1:15–20; Heb 2:5. For Thomas’s teaching on the angels in general, see Serge-Thomas Bonino, Angels and Demons: A Catholic Introduction, Thomistic Ressourcement Series, Vol. 6, Trans. by Michael J. Miller (Washington, DC: The Catholic University of America Press, 2016). Bonino’s work contains an excellent review of the problem of Christ’s headship over the angels in Aquinas and the position of subsequent commentators in ch. 11, ‘Jesus Christ, Head of Angels’, pp. 221–30. See also Bernhard Blankenhorn, The Mystery of Union with God: Dionysian Mysticism in Albert the Great and Thomas Aquinas, Thomistic Ressourcement Series, Vol. 4 (Washington, DC: The Catholic University of America Press, 2016), pp. 215–48. Thomas quotes Dionysius’s Celestial Hierarchies, ch. 7 in III, q. 12, a. 4, s.c.: ‘… the highest angels question Jesus and from him learn the knowledge of the divine work for us, and Jesus teaches them immediately (sine medio)’.

²⁶ ST III, q. 8, a. 4, co., emphasis added.

²⁷ ST III q. 8 a. 4, arg. 1.

²⁸ ST III, q. 8, a. 4, arg. 3.

²⁹ ST III, q. 8, a. 4 ad 1. The third objection, namely, that Christ effects change in human bodies, which angels lack, means that Christ, who gives life to human beings, cannot give life to angels. In his reply to the third objection, Saint Thomas states that the humanity of Christ can cause an effect even in angels ‘on account of his highest union (maximum coniunctionem) to God’. Ambiguously, this is accounted for by an appeal to the power of Christ’s spiritual nature (ex virtute spiritualis naturae).

³⁰ ST III, q. 8, a. 4, ad 2. Notably, this argument underscores the necessity of Christ’s earthly beatific vision inasmuch as it enables Christ’s humanity to be the source of grace and glory from the first moment of his conception. For more on the soteriological character of Thomas’s teaching on Christ’s vision see Joshua Lim, ‘The Necessity of the Beatific Vision in Christ’s Humanity: A Re-Reading of Summa Theologiae III, q. 9’, The Thomist, 86 (2022), 515–42; Joshua H. Lim, ‘“An Encyclopedic Pico della Mirandola?” Re-Thinking Aquinas on Christ’s Infused Knowledge’, Nova et Vetera (English edn), 21 (2023), 147–174; Guy Mansini, ‘Understanding St. Thomas on Christ’s Immediate Knowledge of God’, The Thomist, 59 (1995), 91–124. For a contemporary Thomist account of Christ’s beatific knowledge, see Simon Francis Gaine, Did the Saviour See the Father? Christ, Salvation and the Vision of God (London: T&T Clark, 2015); Thomas Joseph White, ‘The Necessity of the Beatific Vision in the Earthly Christ’, in White, The Incarnate Lord: A Thomistic Study in Christology (Washington, DC: The Catholic University of America Press, 2015), pp. 236–76; Dominic Legge, The Trinitarian Christology of St. Thomas Aquinas (Oxford: Oxford University Press, 2017), pp. 172–86; for a study of Thomas’s doctrine, especially from his biblical commentaries see Charles Rochas, La science bienheureuse du Christ simul viator et comprehensor: Selon les commentaires bibliques et la Summa theologiae de saint Thomas d’Aquin (Paris: Les Éditions du Cerf, 2019); Harkins, ‘Christ’s Perfect Grace and Beatific Knowledge in Aquinas’, pp. 339–72.

³¹ ST III, q. 8, a. 4, ad 3.

³² ST III, q. 59, a. 1, s.c. I am indebted to John Goyette for first bringing this text to my attention.

³³ ST III, q. 59, a. 1.

³⁴ ST III, q. 59, a. 2, co. See also ST III, q. 59, a. 2, co. Throughout the corpus of the article as well as in the various replies to the objections, Saint Thomas repeatedly refers back to the arguments we have seen him use in establishing Christ’s headship based on the principle of propinquity.

³⁵ ST III, q. 59, a. 6, s.c.

³⁶ ST III, q. 59, a. 6, co.

³⁷ Cf., ST III, q. 59, a. 6, co.: ‘Wherefore he also illuminates the angels as Dionysius says in ch. 7 of the Celestial Hierarchy. Thus, it belongs to him to judge them’.

³⁸ ST III, q. 59, a. 6, arg. 1.

³⁹ ST III, q. 59, a. 6, co.: ‘… on account of those things which are done concerning men, of whom Christ is in some special way the head’.

⁴⁰ There is scriptural warrant for such a view (Heb 1:14, which speaks of angels as ministering spirits). In the Gospel narratives we see this in the angels ministering to Christ (Matt 4:11), and Christ sending demons into the herd of swine (8:31). Thomas’s more restricted understanding of Christ’s influence of grace would thus be in keeping with his earlier view found in the DV, q. 29, a. 4, ad 5.

⁴¹ ST III, q. 59, a. 6, co.

⁴² ST III, q. 9, a. 2, co.

⁴³ See ST III, q. 9, a. 2, co.: ‘for it is necessary that that through which others are heated itself be hot’.

⁴⁴ ST III, q. 59, a. 6, co.

⁴⁵ ST III, q. 8, a. 6, co.

⁴⁶ See ST III, q. 8, a. 3, ad 3. Here, too, Saint Thomas’s argument is somewhat ambivalent. He argues to the unity of the members of the Old Covenant with us insofar as they are ultimately ordered to Christ; thus, they are members of the same Church.

⁴⁷ Torrell, ‘S. Thomas et la science du Christ: Une relecture des questions 9–12 de la “Tertia Pars” de la Somme de Théologique’, Saint Thomas au XXe Siècle: Colloque du centenaire de la ‘Revue thomiste’ (1893–1992); Toulouse, 25–28 mars 1993, p. 401.

⁴⁸ ST III, q. 1, a. 3.

⁴⁹ Pace Jean Galot’s characterization of the medieval approach in ‘Le Christ terrestre et la vision’, Gregorianum, 67 (1986), 432.

⁵⁰ Serge-Thomas Bonino, Reading the Song of Songs with St. Thomas Aquinas, Thomistic Ressourcement Series, Vol. 22, trans. by Andrew Levering (Washington, DC: The Catholic University of America Press, 2023), pp. 86–87.

⁵¹ Perhaps one way to state this is to say that Christ’s grace is the universal source with respect to grace in its twofold respect of healing and elevating. It is the fall of man that brings about the need for grace to heal. See ST I-II, q. 109, a. 2, co.; q. 109, a. 3, co. While it is one and the same grace through which humankind is saved, nevertheless grace has a twofold aspect on account of the fallen state of the human soul to which it is applied. Even given such a distinction, however, it is unclear whether this is sufficient to preserve the universality that Saint Thomas attributes to Christ’s headship via the causality of the maximum. Further, to state, as I do, that the grace of the first parents prior to the fall is not mediated by Christ’s humanity is not to say that it does not in some way entail the proleptic glance of faith as did the faith of the Old Covenant Patriarchs and Prophets. Notably, Thomas holds that even prior to the fall there was need for an explicit faith in the mystery of Christ in order to be saved. See II-II, q. 2, a. 7. Briefly, it seems that Thomas can hold this position on account of the predestination of Christ (III, q. 24). Within the broader scope of divine predestination, it is necessary to say that Christ’s humanity was predestined from eternity with a view to the redemption of humanity. See III, q. 24, a. 4, co.: ‘Because [God] foreordained the Incarnation of Christ, he simultaneously foreordained that he would be the cause of our salvation’. This, however, is the matter for another paper.

⁵² ST I, q. 1, a. 5, ad 2.