A Study of Thomas Aquinas’ Baptism of Aristotle’s Ethics
In his paradigm-shifting work on Christian ethics, Alasdair MacIntyre declares, “No doctrine vindicated itself in so wide a variety of contexts as did Aristotelianism: Greek, Islamic, Jewish, and Christian . . . Aristotelianism is philosophically the most powerful of pre-modern modes of moral thought.”  At no place has Aristotelianism had a greater point of intersection with the Christian faith than in the work of Saint Thomas Aquinas. The rediscovery of Aristotelian thought by the medieval theologians saw Thomas emerge as arguably the most prominent Aristotelian scholar of the Middle Ages, which culminated in his systematic application of Aristotelian philosophy to the church doctrines in a way that became the dominant theological understanding of the church for centuries. Alasdair MacIntyre contends that Aquinas’ approach is the successful blending of Aristotle’s moral philosophy with Augustine’s moral theology. “It is widely appreciated that Aristotle is a prominent authority in the Summa Theologiae: Aristotle is referred to in explicit citations almost as often as Augustine.”  In many ways, Aristotle plus Augustine yields Aquinas. Aquinas demonstrates in his Commentary on Aristotle’s Nicomachean Ethics that he understood Aristotle quite accurately on his own terms. In the commentary, he resists the temptation to import a hidden theological agenda onto Aristotle and relies on principles from Aristotle’s natural philosophy and metaphysics to resolve issues in Aristotle’s own work. Aquinas differs significantly from Aristotle in key areas, however, in his own theological writings. While borrowing liberally from Aristotle in constructing a Thomistic moral philosophy, Aquinas intentionally imports ideas from other traditions as well as offering his own original thoughts in intentionally diverging from strict Aristotelian thought. Where Aristotle’s ethics center on earthly well-being achieved through naturally acquired virtue, Thomas’ ethic incorporates Augustine’s theology and its contention that true human completeness exists only in the afterlife and is only attained by a supernatural infusion of faith, hope, and love. This article contends that while Aquinas rightly understood Aristotle, his interaction with Aristotle in his theological works aims at the discovery of higher truth rather than rightly representing Classic Aristotelianism. As Aquinas brings to Aristotelian thought the benefit of divine revelation, he concurrently offers those questions underdetermined by Augustine and the Scriptures the benefit of Aristotle. By briefly tracing a small number of Aquinas’ more significant intentional divergences from Aristotle, grouped under teleological issues and issues pertaining to the will, it will be clear that Aquinas deviates significantly from Aristotle’s ethics while leveraging Aristotle’s framework for the construction of an original Christian virtue ethic.
In Aristotelian teleology, the quality of the performance of rationality is manifest in a notion of “excellence” or “virtue,” and virtue is what makes man good and perform his function well.  The idea that man exists with a certain function to perform couches “Aristotle’s analysis of human practices in terms of means and ends,” and integrates them from the outset into “a kind of metaphysical and speculative framework.”  Adopting Aristotle’s metaphysical framework, Aquinas agrees that everything has a teleological desire to achieve goodness that aims to the final perfection of its operation.  In Books 1 and 10 of the Nicomachean Ethics Aristotle develops his account of man’s end. Aristotle states, “If then there is some end in our practical projects that we wish for because of itself and we do not choose everything because of something else, . . . it is clear this will be the good, i.e., the highest good.”  This highest good is man’s telos, or the “most final end” for which he is purposed. Aristotle suggests that this highest good is not identified with money, honor, or pleasure, but with what he identifies as eudaimonia. Eudaimonia is typically translated as happiness, well-being, or human flourishing. While Aristotle locates man’s end in eudaimonia, he fails to provide definitive arguments for the content of eudaimonia, and instead leaves the definition relatively open. Aristotle does, however, explain that eudaimonia finds its fulfillment in the perfection of reason which leads to a “twofold” ultimate end for man locating supreme happiness in the contemplative philosophical life, and in the result that the philosophical life will lead a man to deliberately choose the secondary happiness of moral virtue within the civic life. This fits Aristotle’s description of man as both a composite being comprised of soul and body, and a naturally political animal. “Aristotle regards ethics as falling within the discipline of statecraft [politics] and written mainly for the benefit of legislators.”  Thus, Aristotle places a strong emphasis on man’s contribution and inclusion in the polis.
From the outset, Aquinas agrees with Aristotle that the virtues are “precisely those qualities the possession of which will enable an individual to achieve eudaimonia and the lack of which will frustrate his movement toward that telos.”  When Aquinas picks up the concepts of telos and eudaimonia, he pairs Aristotle’s framework with the Christian notion that well-being is grounded in life in Christ, and the un-Aristotelian notion that happiness in eternity is far greater than any happiness to be attained in this life.  Aquinas further contends that this teleological principle pervades all of nature, not just humanity, and man has a natural desire for happiness because, like all creatures, his existence is ordered toward his perfection in action by a divine intellect.  Aquinas suggests that every created thing naturally acts and strives for its own perfection, which is realized by all creatures, not in achieving well-being through perfect reason, but instead in assimilation to God who is the highest good and single end of all creatures.  Where Aristotle sees man’s ultimate end in the contemplative philosophical life and contribution to the polis, Aquinas sees man’s end in relationship with God, and in inclusion in His Kingdom.
The theological convictions of Aquinas are a significant divergence from the more naturalistic pre-Christian philosophy of Aristotle. “In the De Caelo Aristotle is presuming that the heavens are living and even divine,” but Aristotle insists that men have no access to the divine and he in no way indicates that his prime mover is a personal being with which people can relate. Aristotle suggests that even the most virtuous of men in the polis cannot be friends with God because friendship is founded on a “kind of equality.”  Friends cannot be so separated in virtue they lack commonality, and friends do not come to love each other when one significantly lacks virtue.  Aristotle contends that man’s separation from the divine is in excess such that no personal relationship exists between them. The gods “greatly exceed men in good things,” and men should never expect to be friends with God because God cannot relate due to their “great difference in virtue.” 
Having the benefit of special revelation, Aquinas incorporates the means of grace by which God enables men to know Him. Aquinas says, “God is supremely lovable in Himself, in as much as He is the object of happiness. But He is not supremely lovable to us in this way, on account of the inclination of our appetite towards visible goods. Hence it is evident that for us to love God above all things in this way, it is necessary that charity be infused into our hearts.”  Additionally, Aquinas shows particular concern for Aristotle’s criteria of “ultimate finality” and “self-sufficiency” for true eudaimonia.  Aquinas asserts that self-sufficiency can only be attributed to God, and ultimate finality accomplished only by the work of God. Thus, in Aquinas’ understanding, there is a pervasive shortcoming in Aristotle’s eudaimonia as it is comprised of only human activities which will always fall short of the fullness of the flourishing Aristotle has in mind. Aristotle’s happiness is an imperfect happiness, which Aristotle himself may have recognized at the end of the discussion of the “Solonic problem” in Nicomachean Ethics chapter 10. In this discussion, Aquinas believes Aristotle casts doubt on whether anyone can be perfectly happy while he is still living. Aristotle concedes that the person “who is active in accordance with perfect virtue . . . through a complete life” is happy, “but happy as a human being.”  Aquinas sees fit to qualify this “happiness in a human way” as an imperfect happiness that cannot compare to the ultimate happiness experienced by higher beings like angels and God.  “From this, Aquinas gleans a third criterion for happiness, “stability of virtuous activity,” in addition to ‘ultimate finality’ and ‘self-sufficiency.’ While Aristotle said, “The good for man is an activity of soul in accordance with virtue . . . in a complete lifetime,” Aquinas counters that perfection and fulfillment of these conditions cannot be achieved in this life.  “Thus continuity and perpetuity, which are not found in the present life, belong to the nature of perfect happiness. Hence perfect happiness cannot be had in this life.”  “Even the [perfect happiness in the contemplative life] does not really meet the Aristotelian criteria of ultimate finality and self-sufficiency,” but is radically deficient.  In Aristotle’s own definition of happiness the human intellect’s aim is to attain truth, but Aquinas argues the intellect can only attain ultimate truth when it rests in the truth itself which is God.  The contemplative life alone cannot reach God, and is again radically deficient in attaining man’s telos which can only come in attaining the truth and universal goodness in relationship with God in direct heavenly union.  This relationship can only come about by the self-revelation of God by which man comes to understand the appropriate orientation and end for his life. For Aquinas, both theological and philosophical considerations require that God be the essence of perfect human happiness because self-sufficiency, stability of virtue, and ultimate finality can only be attained through the promises of God for the afterlife.  God is the intrinsic formal cause of the beatific vision which can only be fulfilled in God by the assistance of His supernatural perfecting grace. While he makes mention of the divine, “Aristotle’s god is not the almighty creator of Aquinas’s theology,” and “Aristotle certainly did not hold that this highest good was best identified with beatific union with God in a resurrected life.”  Aquinas’ theological concerns, specifically the commands of God in Scripture, lead him to see practical wisdom and Aristotle’s principle virtues as insufficient, but needing to be couched in a life of faith and repentance. Given his theological convictions, Aquinas further believes the virtues are best understood as giving more specificity to human reason bound by natural law, understood in the broader context of divine or eternal law. . . . Aristotle does not have a divine law approach to ethics, whereas natural law and a divine legislator provides the framework for discussion of ethics in Aquinas.” 
Additionally for Aquinas, the grace of God makes virtue, and consequently eudaimonia, available to all people. Where Aristotle contends that the effects of having developed a vicious disposition are irreversible and ‘incurable,’ Aquinas rejects this irreversibility of disposition on both theological and psychological grounds.  Theologically, Aquinas follows Augustine where he says “it is indeed in a human’s power to change his will for the better, but there is no power unless it be given by God.”  In Disputed Questions on Truth, Aquinas argues that even in man’s natural power God grants the ability to change and a bad moral disposition never so completely corrupts the soul that a person cannot be led away from vice by reason. 
“Many contemporary scholars agree . . . Aristotle had neither a word nor even the notion corresponding to the medieval (and modern) concept of will” as a faculty distinct from rational cognition.  “The notion of the will was lacking in Aristotle,” and he simply presupposes freedom without having a knowledge of the inherent difficulties.  Aquinas, however, has an elaborate conception of the will built upon a foundation introduced in Christian theology, and has a much more elaborate action theory than Aristotle. Bonnie Kent suggests that “when [Aquinas] explains in the Summa how the mental act of consent differs from other mental acts, he certainly does not appeal to Aristotle. He draws instead on John Demascene and Augustine.”  Whether or not Aristotle allows for true contrary choice is a topic of some controversy, but Aristotle places the moment of choice within the faculty of intellection, and sees the determinate choice as flowing from disposition and reason. Conversely, Aquinas describes the will as a power of the soul separate from both intellect and non-rational inclinations (i.e. emotions and passions), and his views on the will imply that the systematic structure of his action theory and ethics differs from Aristotle’s in a crucial respect. Using Aristotelian language in concert with Augustine’s discussion of human freedom and volition, Thomas creates his own conception of the interaction of the intellect in concert with a secondary faculty, the will, in bringing about free humans acts known as liberum arbitrium. Where Aristotle’s choice issues from the intellect’s dispositions, Aquinas’ will looks to the end action when making a choice between possible potentialities presented to the will by the intellect.  Aquinas specifically assigns to man a liberum arbitrium (free will) which allows man the freedom of deliberation of intellect to choose one of multiple potentialities.  Aristotle states in The Nicomachean Ethics that “choice presupposes deliberation,” and Aquinas shows little hesitation in stepping into Aristotle’s ambiguity and suggesting that election has to be understood as a true choice by which an agent opts for one of multiple possible courses of action.  “Thus the will depends upon the possibilities presented to it by the practical intellect, which guides it to its decisions. Practical reason itself, however, is not determined to one concrete object, for there is a great variety of goods one may pursue.” 
In 3.3 of his Commentary on the Ethics, Aquinas asserts that the immediate result of virtue is not exterior action, but interior choice. For Aristotle, intellectual dispositions determine action in a single act. On Aquinas’ account, however, a human being’s most fundamental action is the “internal act” of choice in which the will settles one course of action proposed by reason. For Aquinas, the “external act” is a secondary phenomenon. This external act is the only action Aristotle speaks of. For Aquinas, however, the will provides a separate adjudicating moment that allows for a person’s action to be informed by their dispositions, but not necessarily determined by them. “At any given moment, reason can focus its attention on objects to which the person is not inclined by his or her already existing dispositions. Consequently, the will can choose differently from what an individual’s virtues would suggest. Thus Aquinas ascribes to virtue a much less determining role than Aristotle did.” It is controversial whether Aristotle believed humans have true freedom to choose between alternative possibilities, or whether they are determined by the disposition of their reason, but for Aquinas choice is closely connected to the ability to act otherwise. Whether Aristotle allows for choice as the product of rational judgment within the intellect or not, it is certain that Aquinas clearly spills more ink on the issue in outlining this second faculty of will to adjudicate the proposals of the rational intellect. Extensive debate surrounds whether Aristotle’s ethics imply Aquinas’ theory of will, or alternatively if Aquinas’ will is a notion that he reads into Aristotle’s theory of action.
What is evident, however, is that Aquinas does something clearly un-Aristotelian in separating the agent’s interior choice from his external action. For Aquinas, it is not the exterior action that is blameworthy or praiseworthy, but the inner choice. For Aristotle, there is no distinction between interior choice and external action.  The choice is equivalent to the external action. If no action has been carried out, no choice has been made.
For Aquinas, the will is essential to morality because he “believes that we are responsible for our actions [only] insofar as we have wills.” Importing an idea from Cicero, which states that circumstances “increase an action’s blameworthiness or praiseworthiness,” Aquinas constructs the concept that moral knowledge and moral choice are informed not only by virtue but by circumstances. “For Aquinas, moral knowledge must cover not only universal rules but also circumstances, that is, the specific features of the agents and their actions.”  Rational judgment implies that the objects of choice are good only from a certain perspective, and objects of human actions are “particular contingent things,” which include many conditions or circumstances.”  “Man is capable of directing his acts . . . in an individual way, because he has intellect and reason. By them he can perceive the different ways in which something is good or bad, depending upon its fittingness for different individuals, times, and places.”  Therefore, on Aquinas’ account, the agent’s choice is always dependent upon his perception of the particulars of his circumstance; and the praiseworthiness or blameworthiness of his choice is dependent insofar as he has the ability to will. Separating interior choice from external action allows for a person to maintain virtuous character and moral fortitude even when their action is compelled against their will, and also places the committing of sins at the heart level (Matt 5:28).
In studying the historical accuracy of Aquinas’ interaction with Aristotle, T. H. Irwin says, Aquinas “does not study Aristotle in order to understand Aristotle, but in order to discover the truth.”  It does not follow therefore that Aquinas commits an anachronism, misunderstands, misrepresents, or even attempts to rehash Aristotle. As Aquinas brings to Aristotelian thought the benefit of divine revelation, he concurrently leverages an Aristotelian framework to answer those questions underdetermined by Augustine and the Scriptures. In his systematic application of Aristotelian philosophy to the church doctrines, Aquinas shaped the church’s understanding of divine truth in a way that arguably no one else has. In considerable ways, Aquinas made significant deviations from Aristotle, but in his own words, “the study of philosophy does not aim at knowledge of what people have thought, but at knowledge of how the truth of things is.” 
***To learn more about Calvinists’ ability and history in embracing Thomas Aquinas’ conception of the human will, see my article on Calvinism and the Free Will Defense.***
Chad W. Hussey is an average Jesus loving iconoclastic non-conformist neighborhood hope dealer from Houston Texas – a husband, father, preacher, and Master of Divinity student at The Southern Baptist Theological Seminary.
Alasdair MacIntyre, After Virtue (Notre Dame, IN: University of Notre Dame Press, 2007), 118.
Michael Pakaluk, “Structure and Method in Aquinas’s appropriation of Aristotelian Ethical Theory” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 49.
Aristotle, Nicomachean Ethics trans. C. Rowe; philosophical introduction and commentary by S. Broadie (Oxford: Oxford University Press, 2002), 2.6.1106a22-4.
Aristotle, Nicomachean Ethics, 59.
St. Thomas Aquinas, Commentary on Aristotle’s Nicomachean Ethics trans. C. J. Litzinger (Notre Dame, IN: Dumb Ox Books, 1993), 1.2 lines 44-46, 184-189.
Aristotle, Nicomachean Ethics, 1.2.1094a18-22.
 Pakaluk, “Structure and Method,” 46-47.
 MacIntyre, After Virtue, 148.
 Aquinas, Commentary, 1.1 line 171.
St. Thomas Aquinas, Summa Contra Gentiles (New York: Aquin Media, 2010), chapters 2-3, 16, 17-24) and St. Thomas Aquinas, Summa Theologiae (Cambridge: Cambridge University Press, 2006), I-II.
Aristotle, On the Heavens trans. W. K. C. Guthrie (Cambridge, MA: Harvard University Press, 1939), 1157b33-1158a1.
Ibid, 1158a36-1159a3; 1158a36-1159a3.
St. Thomas Aquinas, Summa Theologiae (Cambridge: Cambridge University Press, 2006), II-II Q. 24 A. 2.
Aristotle, Nicomachean Ethics, 60.
 Aquinas, Commentary, 10.13 lines 141-4; 10.16 lines 218-222.
Aristotle, Nicomachean Ethics, 1.7.1098a16-18.
 Aquinas, Commentary, 1.10 lines 165-167; 1.14 lines 177-183.
Jorn Muller, “Duplex Beatitutdo: Aristotle’s Legacy and Aquinas’s Conception of Human Happiness” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 62.
Aristotle, Nicomachean Ethics, 6.2.1139b12; and Aquinas, Summa Theologiaie, 1-2.3.7.
Aquinas, Summa Theologiaie, 3.92.1; 102.2.8-9.
Aquinas, Summa Contra Gentiles, 3.25; 3.57.
Candace Vogler, “Aristotle, Aquinas, Anscombe, and the New Virtue Ethics” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 241.
Vogler, “Aristotle, Aquinas, Anscombe,” 241.
Aristotle, Nicomachean Ethics, 3.5.III4b26-III5a3.
St. Augustine, The Retractions (The Fathers of the Church) vol. 2 (Washington, DC: CUA Press, 1968), 22.4.
St. Thomas Aquinas, Quaestiones Disputatae ed. P. Bazzi, M. Calcaterra, T. S. Centi, E. Odetto, and P. M. Pession. 2 vols. (Turin and Rome: Marietti, 1965), 24.2.
 Matthias Perkams, “Aquinas on Choice, Will, and Voluntary Action” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 72.
 Tobias Hoffman, Jorn Muller, and Matthias Perkams, “Introduction” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 11.
 Aquinas, Commentary, 3.1 lines 7-11.
 Aquinas, Commentary, 3.5 lines 34-9; 3.6 lines 116-20.
Aristotle, Nicomachean Ethics, 3.3.
 Bonnie Kent, “Losable Virtue: Aquinas on Character and Will” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 101.
 Aquinas, Commentary, 3.5 lines 18-28.
 Matthias Perkams, “Aquinas on Choice,” 75.
Aquinas, Summa Theologiaie, 1-2.14.3.
Aquinas, Summa Contra Gentiles, 3.113, 14:360a-b.
T. H. Irwin, “Historical Accuracy in Aquinas’s Commentary on the Ethics” in Aquinas and the Nicomachean Ethics ed. Tobias Hoffman, Jorn Muller, and Matthias Perkams (Cambridge, UK: Cambridge University Press, 2013), 14.
Aristotle, On the Heavens, 1.22.8.