Thomas Aquinas’s theology of charity testifies throughout to Paul’s proclamation that “God’s love has been poured into our hearts through the Holy Spirit who has been given to us” (Rom 5:5).1 Charity is a supernatural virtue, infused by God the Trinity in order not only to heal the fallen human will, but also to elevate the human will to a sharing in Trinitarian life. As a deeper participation in the divine love, charity relates the human person in particular to the Person of the Holy Spirit, even though as a created effect in the soul, charity is not the same as the Holy Spirit.2
 Aquinas recognizes that supernatural charity is not the sole foundation of love in the human person. Plato, in the voice of Diotima, describes human beings as “lovers of the good” who desire to possess the good forever; fueled by lack, love desires the “everlasting loveliness which neither comes nor goes.”3 As Plato summarizes the ascent of eros: “Starting from individual beauties, the quest for the universal beauty must find him ever mounting the heavenly ladder, stepping from rung to rung — that is, from one to two, and from two to every lovely body, from bodily beauty to the beauty of institutions, from institutions to learning,” and from learning to the heavenly form or idea of beauty.4 Without directly taking up Plato’s discussion of the erotic ascent, Aristotle adds to it a rich discussion of friendship in Books VIII and IX of his Nicomachean Ethics.
 Many of the most enduring debates about charity have been about the relationship of eros and philia to agape (as used in the New Testament to describe self-giving love).5 In the Summa theologiae, Aquinas discusses amor in his treatment of the sense passions that arise in response to a good.6 He distinguishes amor from dilectio and caritas. Dilectio includes the element of free choice, intellectual consent to the good; while caritas adds to dilectio supernatural elevation of the will to the Trinitarian good, so as to love God and all others in God.7 For Aquinas every love, not only charity, involves the real union and mutual indwelling of the lover and beloved.8 Every love involves an “extasis” or going out of oneself toward the beloved.9 Furthermore, Aquinas appreciates the complexity of the interplay between our sense powers and intellectual powers. The passion of love is integrated into rational love; charity contains the movement of eros.
 As Michael Sherwin has eloquently shown, Aquinas holds that to understand charity one must understand faith, since the intellect and will operate together.10 Faith unites the intellect to God as “First Truth.” Interpreting Hebrews 11:1 Aquinas defines faith as “a habit of the mind, whereby eternal life is begun in us, making the intellect assent to what is non-apparent.”11 First Truth, as the object of faith revealed by God in history, contains the realities of salvation, above all the mysteries of Christ Jesus and the Kingdom of God.12 Relying on Hebrews 11:6, Aquinas teaches that these mysteries can be known implicitly or explicitly, thereby ensuring that not only those who come after the time of Christ can be saved.13 The most profound mystery that we know when our minds are raised by the grace of the Holy Spirit to First Truth is the mystery of the divine Trinity. As Aquinas notes, “God’s sovereign goodness as we understand it now through its effects, can be understood without the Trinity of Persons: but as understood in itself, and as seen by the Blessed, it cannot be understood without the Trinity of Persons.”14 We do not merely understand the Trinity conceptually, but rather the historical missions of the Son and Holy Spirit draw us into the very life of the Trinity.
 If faith is the first step in this union with the Trinity, charity is the “form” of faith because our knowing God is ordered to bearing fruit in love of the Father, Son, and Holy Spirit. The end or goal of our faith in the Trinity is that we share in the divine goodness by loving the Trinity.15 This goal fuels our hope, because faith teaches us to hope that by his salvific power, God will give us eternal communion with himself, infinite triune goodness.16 Following Jesus’ words to his disciples in John 15:15, and indebted also to Aristotle’s Nicomachean Ethics, Aquinas identifies this communion with the Trinity as a “friendship”: God enables us to love him as his friends by establishing a communication (communicatio) and likeness (similitudo) between us and God.17 For Aquinas, as Guy Mansini points out, “communicatio means having goods in common” so as to provide the basis for “friendly concourse.”18
 By communicating to us his blessedness (that is, himself), God causes in us a likeness in love, “a participation of divine charity.”19 This communication comes about in Christ and his sacramental Body, the Church.20 In Christ and through the grace of his Holy Spirit, believers are configured to God’s charitable likeness by means of the sacraments, benevolence, the works of mercy, and so forth. Thus although charity is beyond our natural powers, and although it orders us to eternal communion with the Trinity, charity is no otherworldly virtue. Rather, charity transforms and elevates our natural love so as to build up communities ordered to the common good, the Trinitarian communion of love.21 While in our earthly lives the “communication or fellowship [conversatio]” and “likeness” are imperfect, so that our charity is as yet imperfect, our charity will be perfected in the glory of our heavenly sharing in God the Trinity.22
 I should emphasize that Aquinas denies that the grace of the Holy Spirit gives us charity in proportion to our natural virtue. The gift of charity, while certainly building upon natural virtue, is entirely gratuitous; the fact that we are naturally disposed to friendship does not mean that we have an advantage over others as regards attaining to supernatural charity. As a participation in the divine love, charity enlarges our heart and enables us always to increase in charity during this life. Yet charity can also be lost. Certain actions are incompatible with charity. As the Letter of James teaches, we cannot lay claim to charity while neglecting God or our neighbor; we must “be doers of the word, and not hearers only” (James 1:22). If we freely act against God’s law of love, we thereby lose charity by preferring “sin to God’s friendship, which requires that we should obey his will.”23 Given our weakness, the life of charity depends upon the grace of the Holy Spirit which frees a person to “deny himself and take up his cross and follow me [Jesus]” (Mk 8:34). Servais Pinckaers observes in this regard that “radical self-renunciation is a necessary condition for love of Christ. There is no real charity without detachment and self-renunciation. As love deepens through trial, so its capacity for sacrifice grows stronger.”24
 In charity, we love God and neighbor (as well as ourselves) in the same act, in the sense that our love for God must always include our love of self and neighbor, and our love for self and neighbor must always be ordered to our love for God. At first glance this might appear to be a strange teaching. When we are loving the infinitely lovable God, must we have in view our far less lovable neighbor, let alone ourselves? Aquinas sees things in an eschatological perspective: “the aspect under which our neighbor is to be loved, is God, since what we ought to love in our neighbor is that he may be in God. Hence it is clear that it is specifically the same act whereby we love God, and whereby we love our neighbor.”25 The same holds with our love of self.26 This eschatological perspective is rooted not only in the theology of salvation, but also in that of creation. We love our neighbors, including our enemies, because insofar as they exist, they participate in God the Trinity. We love them as creatures called to attain to the fullness of beatific participation in God the Trinity. Thus we can love them without loving their sins (their lack of participation in God). We do not love irrational animals or demons in this act of charity, because neither irrational animals nor demons can share in the Trinitarian communion; although in another sense we do love them in charity by wishing them to endure (and glorify God) as regards their natural being which is good. Charity has a particular order defined by relation to the good and by obligations that we have with regard to others’ welfare.27
 Quoting Étienne Gilson’s remark that “the most marvelous of all things a being can do is to be,” Josef Pieper attempts to describe the basis of love: “For what the lover gazing upon his beloved says and means is not: How good that you are so (so clever, useful, capable, skillful), but: It’s good that you are; how wonderful that you exist!”28 God’s creative act, pouring forth the goodness of finite being, is sheer love. God loves us into existence and rejoices in created goodness: “And God saw everything that he had made, and behold, it was very good” (Gen 1:31). When by God’s gift we experience the joy of loving God in himself — his Trinitarian communion — our joy also involves peace; our rational appetite finds its fulfillment in loving the infinite goodness of God (and the participated goodness of our neighbors).
 Faced with evils or defects in goodness, the charitable person’s response is mercy. God has mercy upon us by bountifully healing our defects through his causal love, and in light of our defects we have mercy on each other by seeking to do good to each other. As regards outward acts, this manifests itself as beneficence — the bestowal of gifts — and the works of mercy, among which Aquinas numbers “to feed the hungry, to give drink to the thirsty, to clothe the naked, to harbor the harborless, to visit the sick, to ransom the captive, to bury the dead,” as well as “to instruct the ignorant, to counsel the doubtful, to comfort the sorrowful, to reprove the sinner, to forgive injuries, to bear with those who trouble and annoy us, and to pray for all.”29 The works of mercy also include fraternal correction, to which Aquinas gives special place because of its difficult but necessary role in sustaining the communion of the people of God.
 In all these ways, we say to the beloved, whether God or our neighbor: “It’s good that you are; how wonderful that you exist!” We say this not merely on the natural level, but in light of God’s gift of a participation in his own Trinitarian life, eternal life with the Father, Son, and Holy Spirit. With the Father, Son, and Spirit we proclaim, “It’s good that you are; how wonderful that you exist!” In this proclamation, when it attains its fullness in interpersonal communion, is the joy and peace of charity.
 By contrast, the sins against charity bespeak the opposite of this joy and wonder in another’s existence. Far from rejoicing in God or neighbor, hatred sees the existence of God or neighbor as opposed to our own good. The freshness of joy and wonder is lost in sloth, which sorrows rather than exults about God’s gifting, with the result that the slothful person falls into despair, cowardice, sluggishness, spite, malice, and unlawful bodily pleasures. In its selfish joylessness, envy cries out, “How sad it is that you exist more perfectly than I do!” rather than “How wonderful that you exist!” Discord and contention, rooted in pride, set up one’s own opinion over against the gift of communion with God and neighbor; joy and wonder are squelched by the desire to dominate others. Schism severs the visible unity of the people of God, the Body of Christ to which we should rather respond, with ever greater praise, “How wonderful that you exist!” War, as unjust slaughter driven by the desire to dominate, destroys the earthly existence of people and communities; and strife and sedition aggressively seek to harm others. Scandal actually seeks the eternal spiritual harm of others. How profoundly opposed these actions are to joy and wonder in another’s being!
 Aquinas does not suppose that charity is contrary to law, although he recognizes that as Paul says, “where the Spirit of the Lord is, there is freedom” (2 Cor 3:17).30 As Aquinas puts it, “The obligation of a precept is not opposed to liberty, except in one whose mind is averted from that which is prescribed.”31 Following Jesus (and Paul), he identifies charity as the goal of the Torah. He recalls Jesus’ words in Matthew 22:37–40, where Jesus responds to a scribe’s question about the greatest commandment of the Torah: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the great and first commandment. And a second is like it, You shall love your neighbor as yourself. On these two commandments depend all the law and the prophets.”32 The Gospel of John reports similar words of Jesus that make clear that Jesus’ Cross fulfills the Torah: “This is my commandment, that you love one another as I have loved you” (Jn 15:12; cf. 1 John 4:21).33 Likewise Paul explains that “he who loves his neighbor has fulfilled the law” (Rom 13:8).
 Although the Decalogue does not contain the commandments to love God and neighbor, which are found instead in Deuteronomy 6:5 and Leviticus 19:18 respectively, Aquinas notes that as regards our natural capacities, these two commandments are “the first general principles of the natural law,” which inclines toward the good.34 When supernatural charity fulfills the Torah by making us friends of God and neighbor, the grace of the Holy Spirit infuses in the charitable person the moral virtues needed for such friendship.35 Such bountiful divine gifting accords with Jesus’ promise to transform us: “If a man loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him” (Jn 14:23). On the other hand, Aquinas retains an eschatological dimension in his account of our fulfillment of the Torah through charity. Perfect fulfillment of the law of love requires the perfect union with God attained only in the final consummation, when God is “everything to every one” (1 Cor 15:28).36 Until then, humans fulfill the law of love only imperfectly and to varying degrees, although Aquinas makes clear that such imperfection has to do with the extent, intensity, and effect of love, not with the will’s actually cleaving to something opposed to charity.37
 Aquinas concludes his discussion of charity in the Summa theologiae by exploring the gift of the Holy Spirit that specially enhances our ability to live the charitable life: the gift of wisdom.38 Following the patristic and medieval exegetical tradition, his understanding of this gift relies upon Isaiah and Paul. According to Isaiah, the Davidic Messiah will possess the Spirit of the Lord, “the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and the fear of the Lord” (Is 11:2).39 In Christ, believers share in these gifts. Aquinas cites 1 Corinthians 2:10 and 2:15, where Paul seeks to show that “we have the mind of Christ” (1 Cor 2:16) because we “receive the gifts of the Spirit of God” (1 Cor 2:14) who “searches everything, even the depths of God” (1 Cor 2:10). In the person who has faith and charity, the gift of wisdom makes it possible to judge the truth of divine realities “on account of connaturality with them,” and not merely by study.40 The gift of wisdom assists in guiding our action so that it accords with God’s law of love. With Augustine, Aquinas associates this gift with the beatitude “Blessed are the peacemakers, for they shall be called sons of God” (Mt 5:9). Charity and wisdom unite in the effect of peace and configure us to the image of Wisdom incarnate, Jesus Christ.41
1. See Thomas Aquinas, Summa theologiae, trans. Fathers of the English Dominican Province (Westminster, MD: Christian Classics, 1981 ), II–II, q. 24, a. 2, sed contra. This essay is drawn from my The Betrayal of Charity: The Sins that Sabotage Divine Love, forthcoming from Baylor University Press.
2. For background to Aquinas’s discussion of charity, see Michael Sherwin, O.P., “Aquinas, Augustine, and the Medieval Scholastic Crisis concerning Charity,” in Aquinas the Augustinian, ed. Michael Dauphinais and Matthew Levering (Washington, D.C.: Catholic University of America Press, 2007) 181–204; Robert Wielockx, La discussion scholastique sur l’amour d’Anselme de Laon à Pierre Lombard d’après les imprimés et les inédits (Ph.D. dissertation, Catholic University of Louvain, 1981).
3. Plato, Symposium, trans. Michael Joyce, in The Collected Dialogues of Plato including the Letters, ed. Edith Hamilton and Huntington Cairns (Princeton: Princeton University Press, 1961), 206a (p. 558) and 211a (p. 562); cf. 201b (p. 553).
4. Ibid., 211c (pp. 562–63). For discussion see L. A. Kosman, “Platonic Love,” in Eros, Agape, and Philia, ed. Alan Soble (St. Paul, MN: Paragon House, 1989) 149–64; Robert E. Wagoner, The Meanings of Love: An Introduction to Philosophy of Love (Westport, CT: Praeger, 1997) chapter 2.
5. See Ceslaus Spicq, O.P., Agape in the New Testament, 3 vols. (St. Louis, MO: B. Herder Book Co., 1963). See also Søren Kierkegaard, Works of Love: Some Christian Reflections in the Form of Discourses, trans. Howard and Edna Hong (New York: Harper & Row, 1962), for a radical rejection of eros and philia.
6. See I–II, q. 25, a. 2.
7. I–II, q. 26, a. 3.
8. See I–II, q. 28, aa. 1–2.
9. See I–II, q. 28, a. 3.
10. Michael Sherwin, O.P., By Knowledge and By Love: Charity and Knowledge in the Moral Theology of St. Thomas Aquinas (Washington, D.C.: Catholic University of America Press, 2005).
11. II–II, q. 4, a. 1. See Romanus Cessario, O.P., Christian Faith and the Theological Life (Washington, D.C.: Catholic University of America Press, 1996).
12. II–II, q. 2, a. 7.
13. See II–II, q. 2, a. 7, ad 3 and elsewhere.
14. II–II, q. 2, a. 8, ad 3.
15. II–II, q. 4, a. 3.
16. II–II, q. 17, a. 2.
17. See II–II, q. 23, a. 1, including the sed contra.
18. Guy Mansini, O.S.B., “Similitudo, Communicatio, and the Friendship of Charity in Aquinas,” Recherches de théologie ancienne et médiévale, Supplementa vol. 1: Thomistica, ed. E. Manning (Leuven: Peeters, 1995): 1–26, at 5. Mansini draws upon Joseph Bobik, “Aquinas on Friendship with God,” New Scholasticism 60 (1986) 257–71. For background see also Jean-Pierre Torrell, O.P., “La charité comme amitié chez saint Thomas d’Aquin,” La Vie spirituelle no. 739 (2001) 265–83; Bobik, “Aquinas on Communicatio: The Foundation of Friendship and Caritas,” Modern Schoolman 64 (1986) 1–18; Mansini, “Aristotle on Needing Friends,” American Catholic Philosophical Quarterly 72 (1998) 405–17; Anthony W. Keaty, “Thomas’s Authority for Identifying Charity as Friendship: Aristotle or John 15?,” The Thomist 62 (1998) 581–601.
19. II–II, q. 23, a. 3, ad 1; see also II–II, q. 24, a. 2.
20. See Mansini, “Similitudo, Communicatio, and the Friendship of Charity in Aquinas,” 10–11; Bobik, “Aquinas on Friendship with God,” 269–70; L. Gregory Jones, “The Theological Transformation of Aristotelian Friendship in the Thought of St. Thomas Aquinas,” New Scholasticism 61 (1987) 373–99, at 385.
21. See Michael Sherwin, O.P., “St. Thomas and the Common Good: The Theological Perspective: an Invitation to Dialogue,” Angelicum 70 (1993) 307–28, especially 310–13; Jeanne Heffernan Schindler, “A Companionship of Caritas: Friendship in St. Thomas Aquinas,” in Friendship and Politics: Essays in Political Thought, ed. John von Heyking and Richard Avramenko (Notre Dame: University of Notre Dame Press, 2008) 139–62, especially 151–56; Romanus Cessario, O.P., The Moral Virtues and Theological Ethics (Notre Dame: University of Notre Dame Press, 1991). See also Thomas M. Osborne’s discussion of the limitations of pagan virtue: “The Augustinianism of Thomas Aquinas’s Moral Theory,” The Thomist 67 (2003) 279–305. Osborne’s key point concerns the unity of the virtues: “Although Thomas thinks that pagans without charity can have true virtues, he does not think that they can lead morally virtuous lives” (303).
22. II–II, q. 23, a. 1, ad 1.
23. II–II, q. 24, a. 12. This paragraph briefly summarizes question 24. For related discussion see Lawrence Dewan, O.P., “St. Thomas, James Keenan, and the Will,” in Dewan, Wisdom, Law, and Virtue: Essays in Thomistic Ethics (Bronx, NY: Fordham University Press, 2007) chapter 9.
24. Servais Pinckaers, O.P., The Sources of Christian Ethics, trans. Mary Thomas Noble, O.P. (Washington, D.C.: Catholic University of America Press, 1995) 30.
25. II–II, q. 25, a. 1.
26. See II–II, q. 25, aa. 4–5.
27. This paragraph briefly summarizes questions 25 and 26.
28. Josef Pieper, Faith, Hope, Love, trans. Richard and Clara Winston (San Francisco: Ignatius Press, 1997) 170; Gilson’s remark is from his History of Christian Philosophy in the Middle Ages (London: 1955) 83.
29. II–II, q. 32, a. 2. See also David Bentley Hart, Atheist Delusions: The Christian Revolution and Its Fashionable Enemies (New Haven, CT: Yale University Press, 2009) 29–31.
30. Cited in II–II, q. 44, a. 1, obj. 2.
31. II–II, q. 44, a. 1, ad 2.
32. This passage is cited in II–II, q. 44, a. 1; q. 44, a. 3, sed contra; q. 44, a. 4.
33. Aquinas cites 1 John 4:21 in II–II, q. 25, a. 1, sed contra and q. 44, a. 2, sed contra; he cites John 15 in II–II, q. 23, a. 1, sed contra.
34. I–II, q. 100, a. 3, ad 1.
35. See I–II, q. 65, a. 3.
36. II–II, q. 44, a. 6.
37. See II–II, q. 44, a. 6; II–II, q. 184, a. 2, especially ad 3.
38. See Romanus Cessario, O.P., Introduction to Moral Theology (Washington, D.C.: Catholic University of America Press, 2001) 205–12; Pinckaers, The Sources of Christian Ethics, 152–55, 224–31.
39. Cited in II–II, q. 45, a. 1, sed contra.
40. II–II, q. 45, a. 2.
41. See II–II, q. 45, a. 6.