1. See Thomas Aquinas, Summa theologiae, trans. Fathers of the English Dominican Province (Westminster, MD: Christian Classics, 1981 [1920]), 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.