Luther’s Certainty of Faith: Thomistic Hope or Presumption?

Reading Time: 13 minutes

By Sam Agra: St. Louis University

Is the Christian believer assured of his or her salvation and, if so, to what extent? Are we bound to an once saved always saved method by which we achieve complete eternal security by a personal act of faith in Jesus, or must we continually fear our damnation and wretchedness in comparison to God’s perfect judgement? Christian theologians since the very beginning have pondered this question, and the touchstone thinkers examined in this paper, Aquinas and Luther, are no exception. Luther, in the early 16th century, found himself in the latter position, dreading every fault and in constant despair of his state before Christ. Through the development of his famous doctrine of justification by faith alone which has shaped theological discourse ever since, Luther comes to the conclusion that the Christian in and through faith may be assured, in a certain sense, of his salvation. To Catholics who have grown up with the teachings of confession, mortal sin, and the sacraments, Luther’s proclamation sounds prima facie like a ludicrous claim. 

This case, of course, requires more nuance, for Thomas Aquinas himself, foremost of Catholic theologians, taught in his Summa Theologiae that there is a certainty of salvation in the hope of the living Christian. Aquinas, however, distinguishes this certain hope from one of its privations, the vice of presumption. The task of this short paper is, then, to give an examination of Luther’s certainty of faith based on the Thomistic distinction between the certainty of hope and that of presumption. The main primary sources I will employ are Aquinas’s Summa and Luther’s The Freedom of a Christian. Through a careful examination and comparison of these three terms, Luther’s faith and Thomas’s hope and presumption, I will conclude that though Luther’s conception of faith involves total dependence on God, a trust in His saving power, and an integration of acts of charity toward God and neighbor, all aspects which appear in Thomistic hope and Aquinas’s understanding of the efficient means of salvation, insofar as Luther’s faith does no trequire one essentially to commit good works or turn from sin, his doctrine of the certain of faith falls under Thomas’s condemnation of presumption. I will proceed by examining Aquinas on hope and then Luther on faith both in its essence and its certainty and will note similarities between the two. Next, attempting to contrast the two thinkers, I will turn to Aquinas on presumption and Luther on the role of works. Finally, I will show how Luther’s understanding of works more closely aligns him with Thomistic presumption rather than hope.

The first task of this paper is to set forth Aquinas’s teachings on the virtue of hope and its certainty toward salvation. Aquinas defines hope within the larger context of the three theological virtues: faith, hope, and charity. These virtues are infused by God’s direct gift to one in grace, have their final end in God, and are perfective of the person to whom they are given. Hope is that virtue which exists in, perfects, and assists the will as it strives toward the difficult end of heaven and eternal union with God. Hope is what allows one to continue pursuing Christ in the face of difficult circumstances. The fact that hope exists in the will and directs us toward a future divine union distinguishes it from faith which exists in the intellect and charity which unites our will to God in this life. Since the end of heaven, the goal of hope, is entirely beyond human power alone, the virtue of hope rests and trusts in the power of God to accomplish this, that is to say, hope has God as its efficient cause in addition to its final cause.

It is due to the efficient nature of hope that Aquinas can say that the hope of a wayfarer, a Christian in this life, is certain of its completion. That is, hope carries with it an assurance of salvation. To understand what Aquinas means by the certainty of hope, we must briefly examine that upon which hope is built: the certainty of faith. In Aquinas’s discussion of faith, he notes that, “Science is not more certain than faith; nor is anything else.” He explains that understanding which has a more certain cause is itself more certain. Thus, an experiment understood via a rigorous application of the scientific method is more certain than one based upon a guess. However, since faith is founded on the direct revelation of God who can neither err nor deceive, it follows that nothing is more certain than faith, considered in its cause. Though on the part of the subject, the one with faith, faith may seem uncertain, this does not lessen the objective certainty. It is, rather, a defect in our own grasping of the truth.

Returning to the discussion of hope, the mere existence of hope necessitates the presence of faith. Hope draws upon the intellectual certainty of faith and attaches to this certainty its own trust in God’s mercy and ability to affect our salvation. By faith, God’s mercy and ability to save are known with certainty, so by trusting in these truths via hope, the wayfarer is assured of his salvation. As Stephan Furtner explains, “Since… God in his mercy and omnipotence is perfectly reliable, the hope of salvation also gains an absolute certainty.” However, two important caveats must be drawn here from the objections in the same article. In the second Aquinas argues that since no one can know that she is in a state of grace, there can be no certainty. In the third objection he notes that those who initially have the virtue of hope may fail to attain heaven and thus there can be no certainty in hope. The certainty of hope does not, Aquinas says, depend on whether one will be in a state of grace tomorrow or at any one time save the moment of death. Hope trusts in God’s ability to bring about this state of grace at or before the moment of my death. Further, my trust in His mercy lets me know that He desires my salvation. Second, the falling of one into hell is not due to a lack of divine power or mercy, that in which the certainty of hope is found. Rather, Aquinas argues, a soul does not obtain heaven due to her free will placing the obstacle which is mortal sin between herself and God’s mercy. Thus, the nuanced certainty of Thomas’s hope is not a case of logical necessity where all those with hope must attain salvation in the same way that any real number multiplied by zero will equal zero. Rather the certainty of hope is similar to the certainty by which a patient, trusting in the ability and goodwill of his doctor and barring his own resistance, knows that his simple malady will be cured.

While Aquinas places this trusting aspect within hope, keeping faith within the intellect, Luther’s faith has both intellectual and trusting aspects. As the argument transitions to an examination of Luther, the immense role which faith plays in his theology must be briefly mentioned. Luther’s revolutionary concept in the world of theology was the justification of believers sola fide. A Christian is brought into right relationship with God, justified, by faith in Christ alone. Luther developed this doctrine against what he saw as the semi-Pelagian theology popular in his time. In his Smalcald Articles, a Lutheran counter-council in response to the calling of Trent, it is written, “[we are] justified without merit by his [Christ’s] grace, through the redemption that is in Christ Jesus by his blood… It is clear and certain that this faith alone justifies us…” The act of faith, and nothing else, is that by which we are called righteous and worthy to enter paradise, according to Luther. 

To understand the relationship of Luther’s faith to Thomistic hope, we must first understand what Luther means by the word “faith.” While Luther’s understanding of faith is nuanced and complex, I note two aspects of it essential to the discussion at hand: personalization and trust. First, faith always has a strong personal dimension. It is not merely an intellectual assent as if one may assent to “Christ is risen” in the same manner that she will agree that, “There exists a force which pulls objects earthward.” Luther rejects this view of faith which stops at a mere conceptual level. He distinguishes between false and true faith, writing that false faith is when one says, “’I believe that the Son of God suffered and rose again.’ But true faith says ‘ I certainly believe that the Son of God suffered and rose, but he did this all for me’… Accordingly, that ‘for me’ or ‘for us,’ if it is believed creates that true faith… that alone justifies.” Faith requires a personalization of the articles of faith. This effective and justifying faith both knows that the historical events of salvation occurred and that they occurred, “for me and for my sake, This ‘for me’ is the decisive and essential fact which definitely distinguishes it from everything else which we otherwise call faith.” Second, faith, like Thomistic hope, has an element of trust. It not only recognizes that the facts of salvation were done for me, but it clings to these beliefs. Robert Kolb notes that in Luther’s study of Greek he “learned that pistis [faith] referred to the trust that clings to an object, particularly a person,” where the person referred to is Christ. This aspect of faith is clearly added to his theology on the topic. Luther himself defines faith at one point as “A certain trust in the heart and a firm assent through which Christ is grasped.” Note how faith has both an intellectual and trusting aspect which is not entirely dissimilar to one who possesses Thomas’s faith and hope. Luther’s faith, as has been shown, is a personal acceptance and application of the truths of salvation history to one’s own life combined with an interior trust which clings to Christ.

Having a basic understanding of faith in Luther’s mind, the paper can proceed to the relation of faith to certainty. Recall that hope for Aquinas has a certainty based upon the ability of God to save and His merciful desire to do so, if the believer does not create the impediment to grace which is mortal sin. Luther’s notion of the certainty of faith, in my interpretation, is similar with a few important differences. This paper will examine three aspects: the theocentricity of faith’s certainty, its knowledge that one stands in right relation to God, and the inability of anything to remove this certainty.  First, we must see the main tension of Luther’s certainty, one that saves him from being easily distanced from Thomas’s hope. Sven Grosse writes, “[Faith] trusts with assurance that the believer is acceptable to God, that his sins are forgiven, and that he will attain eternal life… [On his own] the believer has no self confidence, and, before God, gives up his own ability to judge—gives up that discernment through which he might judge himself to be free from sin, or his works to be good, or that he will attain eternal life.” As Aquinas’s hope is purely theocentric, so is Luther’s. The believer is certain of salvation because God judges him so, not due to anything on his part, apart from God. Were Luther to assert that this confidence came from human self-estimation, his faith would clearly be something different than Thomistic hope. 

Second, note that Luther’s certainty of faith is both closely related to one’s place before God and the non-ability of anything to separate the believer from God. Referring to Luther’s lectures on Romans, Sven Grosse writes, “In Rom 8:33: ‘Who will bring any charge against God’s elect?’ means that ‘we are certain that no sin will be charged against us,’… Finally, [Luther] declares in Rm 8:38 that he is certain that nothing will separate him from the love of God.” The Christian is certain that nothing will take her away from God, since God is all powerful and desires the believer’s salvation, and that God will charge no sin, that is nothing damnable, to her. Toward the first point, I must note a connection and add a qualifier. See how the inability of an outside power to take away salvation is linked to the theocentric operation of faith: 

Now, since God has taken my salvation out of my hands into His, making it depend on His choice and not mine, and has promised to save me, not by my own work or exertion but by His grace and mercy I am assured and certain both that He is faithful and will not lie to me, and also that He is too great and powerful for any demons or any adversaries to be able to break Him or to snatch me from Him…

Because the certainty of faith is based entirely in God’s hands, and God is omnipotent, it follows that it is impossible for one to be taken from this certainty by “any adversaries.” The qualifier regards how one who is a Christian, then, may ever be lost. Luther does not advocate a “once saved always saved” theology. Grosse summarizes Luther’s thought on the certitude of faith, writing, “If he believes, and so long as he believes, his future salvation is assured, and he is also certain of his election.” The lack or loss of faith in Luther’s thought plays an analogous role to the obstacle of grace in Thomas’s.

While the lack or loss of faith ends one’s certainty for Luther, it is this obstacle of grace that harms Thomas’s certainty of hope. The obstacle can take the form of presumption, one of the privations of hope. Presumption can be of the “lazy” or “Pelagian” types. As Luther’s faith is clearly nowhere near any type of Pelagianism, it is the “lazy” presumption that we will focus upon here. Thomas discusses this vice in II-II q.21. He calls presumption a sort of unbecoming hope, whereby we desire and expect to achieve something of God in a manner unfitting to Him. Strictly speaking, presumption is when “a man tends toward some good as though it were possible by the power and mercy of God, whereas it is not possible, for instance, if a man hope to obtain pardon without repenting or glory without merits… by presuming thus a man removes or despises the assistance of the Holy Spirit, whereby he is withdrawn from sin.” For Thomas, the certainty of hope requires that one, assisted and led by grace first, repent from her sins and obtain merit through good works. In other words, “it is false that He grants forgiveness to those who persevere in their sins and that He gives glory to those who cease from good works.” 

Thomas’s conception of salvation requires the graced cooperation of the human person. The obstacle to the certainty of hope, the obstacle which would then turn hope into a false presumption, would be the refusal of a person to cooperate. Wawrykow writes that this kind of presumption, as opposed to a Pelagian presumption, is that kind which one is intent on leaving everything to God and ignores what God wants of those whom He wishes to bring to salvation. David Elliot makes the point that lazy presumption is the belief that God is so overwhelmingly merciful that salvation requires no contrition for sin, amendment of life, or good works. In sum, presumption for Thomas is a hope which does not recognize the necessary human cooperation with divine grace through the performance of good works or the repentance of sins. Both are necessary to have a true hope and a true certainty.

The question for Luther, then, is to what extent if any are repentance and works necessary in his conception of the faith and its certainty? If they are not necessary, then Luther, according to Thomas, is presumptuous; if necessary, then Luther is merely asserting Thomistic hope under a different name. Here, one may be tempted to simply quote Luther in The Freedom of a Christian, where he writes, “We are justified by faith alone, it is clear that the inner person cannot be justified, freed, or saved by any external work or act,” and conclude that Luther is indeed presuming salvation. To make such a direct comparison would be to play with definitions rather than make a true argument. We must first lay down more nuance. For when Luther refers to works here, he means something different than Aquinas. As Wawrykow notes in his Article, Luther’s trusting faith excludes any concept of merit while Thomas’s trusting hope allows it. This means that in Aquinas, works for merit are acts done primarily by God working through an aligned human will, though these acts are also truly human acts. When Luther refers to works here, however, he means that works qua human participation apart from divine grace cannot bring us to salvation. While Aquinas would seem to agree with this conclusion, insofar as humans are unable to merit the “first grace” of justification itself, his conception of the noncompetitive nature of the divine and human will means that he must allow works some role in salvation, even if construes these works in a manner that avoids Pelagianism. Luther has no concept of non-Pelagian merit earned in and through grace. Thus, he must reject every idea that works and human acts, be they of charity or repenting from sin, have a role in the salvation of the believer.

Does this difference in the conception of works save Luther from presumption? I think not. For presumption clearly includes thinking that God will bring about my salvation without my own cooperation. Luther writes, “Let us be clear that no one needs do these things [serve his neighbor] to attain righteousness and salvation.” According to Luther, there is no need for works to attain salvation, an idea that would easily fall under Thomas’s notion that it is “false that He… gives glory to those who cease from good works.” Luther affirms elsewhere that, “Such a person does not need works in order to be righteous and saved. Faith alone confers all these things in abundance; however, if a person were to be so foolish as to presume that a good work is needed to become righteous, free, saved, and Christian, then faith and all its benefits would be lost instantly.” The presumption that good works are necessary for salvation would effectively be the loss of trust in God’s saving power and thus in faith.

However, Luther himself and his later commentators are quick to respond to the charge of a lazy Christianity, one in which there is no room or need for works. For while works are unnecessary in one sense, they are entirely needed in another. They do not justify, yet they come from justification. As Luther writes, “From faith there flows a love and joy in the Lord. From love there proceeds [the service of neighbor.]” It would be a strawman if one were to argue that Luther had no role for good works in his theology. Works are necessary insofar as we expect them from a believer and they ought to come from faith, but following the above quotes, we note that they are extrinsic to faith. Richard Olmstead notes that salvation occurs by faith alone, but faith is never alone. That is, works follow faith by a necessity of nature rather than obligation. Olmstead’s interpretation fits with my own and would be an example of Thomistic presumption, as works as extrinsic to faith and its certainty, though they flow from it. 

However, there are commentators of Luther’s thought who will make this point more strongly. Kolb thinks that the production of works by faith is simply “axiomatic.” One can still read Kolb in a manner which places works as extrinsic to faith and its certainty, but an axiomatic connection is certainly closer than one of “necessity of nature.” Janz seems to make the point that works are essentially a part of faith when he notes that true faith “never” exists without good works – in fact Luther would call a faith without works, according to Janz, a “false faith.” If it is the case that “faith without works is dead” or a false faith, then it would seem to follow that works are intrinsically necessary, rather than extrinsically necessary, to faith. His assertion, however, does not seem to align with Luther’s own words. Multiple times above I have noted where Luther asserts that works follow but are not intrinsic to faith or its certainty. Again, he writes, “Christian freedom does not lead us to live lazy and wicked lives but makes the law and works unnecessary for righteousness and salvation.” Works may even axiomatically follow from faith, but to say that they are necessary for faith is to go beyond Luther’s own words.

To conclude, despite the strong similarities between Aquinas’s conception of hope in its certainty with Luther’s certainty of faith, Luther’s faith is more correctly considered as analogous to Thomistic presumption than hope. Presumption for Thomas occurs when one hopes, that is, trusts in God and is certain about salvation without thinking it necessary for this hope and certainty that he turn from sin or perform good works. In short, to hope with certainty a Thomist must act. In contrast, Luther’s trusting faith places human acts decidedly outside of the trust and certainty of faith. Thought good acts follow from faith, to include them in part of one’s trust in God would be to lose faith.


Aquinas, Thomas. Summa Theologiae. Translated by the Fathers of the English Dominican Province (Newadvent: 2017).

Elliot, David. Hope and Christian Ethics. New York: Cambridge University Press, 2017.

Grosse, Sven. “Salvation and the Certitude of Faith: Luther on Assurance.” Pro Ecclesia 20, no. 1 (Wint 2011): 64-85

Hannah, John D. “The Meaning of Saving Faith: Luther’s Interpretation of Romans 3:28.” Bibliotheca Sacra 140, no. 560 (October 1983): 322-34.

Kolb, Robert. Luther’s Treatise On Christian Freedom and Its Legacy. Lanham: Fortress Academic 2020. 

Janz, Denis. The Westminster Handbook to Martin Luther. Louisville: Westminster John Knox Press, 2010.

Luther, Martin. “Academic Disputation of 1535.” In Denis R. Janz, The Westminster Handbook to 

Large Catechism. In Kolb Luther’s Treatise

Luther’s Works, The American Edition. In Jared Wicks, “Justification and Faith in Luther’s Theology,” Theological Studies 44, no. 1 (March 1983): 3-29.

The Freedom of a Christian. Translated by Mark D. Travik. Minneapolis Fortress Press 2008.

Smalcald Articles. First article. In Timothy F. Lull and William R. Russel eds. Martin Luther’s Basic Theologica Writings. Minneapolis: Fortress Press 2012.

Olmstead, Richard. “Staking all on faith’s Object: The Art of Christian Assurance According to Martin Luther and Karl Barth.” Pro Ecclesia 10, no.2 (Spr 2001): 135-58.

Pfurnter, Stephan. Luther and Aquinas on Salvation. New York: Sheed and Ward, 1965.

Wawrykow, Joseph P.  “The Theological Virtues.” In Brian Davies and Elenore Stump eds. The Oxford Handbook of Aquinas (Oxford: Oxford University Press, 2012), 287-304.

One Response

  1. In the New Testament, the Holy Spirit plays a prominent part in our certainty of salvation. He is the first installment or down payment of our inheritance: and the one who seals us (see Ephesians 1:14, 4:30).
    His presence within us gives us the knowledge that Christ lives in us (see 1John 4:23-24).

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