Although we think of Luther’s famous 95 theses as sparking the Reformation in 1517, it would perhaps be more accurate to accord this honor to the theses that he prepared for the disputation in Heidelberg in 1518. It was at this event that Luther laid the foundation and set the trajectory for his later reforming work. In the scheme of things, the 95 theses penned in Wittenberg took aim at a fairly narrow set of issues, whereas the theses composed for Heidelberg set forth, in seminal form, Luther’s comprehensive vision for the church reformed under the authority of the Word of God. This comprehensive vision can be summed up in Luther’s own phrase theologia crucis — theology of the cross — in contrast to the theologia gloriae — the theology of glory — that he vociferously opposed in medieval scholasticism. It was here, not in the matter of indulgences, but between the theologies of cross and glory, that Luther drew his main line of battle. Stated simply, if we do not understand the theology of the cross, we cannot understand Luther. Speaking personally, I find this aspect of Luther’s teaching to be the most significant, most compelling, and most encouraging of everything that he ever said or wrote.
What is the theologia crucis? Entire books deal exclusively with this subject, so a mere blog post can hardly serve to do it justice. However, I think it is possible to get an adequate, if only cursory, sense of what Luther meant simply by sampling a few of the Heidelberg theses. Beginning with thesis 19, Luther argued:
19. That person does not deserve to be called a theologian who looks upon the invisible things of God as though they were clearly perceptible in those things which have actually happened [Rom. 1:20].
This is apparent in the example of those who were “theologians” and still were called fools by the Apostle in Romans 1[:22]. Furthermore, the invisible things of God are virtue, godliness, wisdom, justice, goodness, and so forth. The recognition of all these things does not make one worthy or wise.
20. One deserves to be called a theologian, however, who comprehends the visible and manifest things of God seen through suffering and the cross.
The “back” and visible things of God are placed in opposition to the invisible, namely, human nature, weakness, foolishness. The Apostle in 1 Corinthians 1[:25] calls them the weakness and folly of God. Because humans misused the knowledge of God through works, God wished again to be recognized in suffering—to condemn wisdom concerning invisible things by means of wisdom concerning visible things, so that those who did not honor God as manifested in the Divine works should honor God hidden in suffering. As the Apostle says in 1 Corinthians 1[:21], “For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach to save those who believe.” Now it is not sufficient for anyone, and it does one no good to recognize God in Divine glory and majesty, unless one recognizes God in the humility and shame of the cross. Thus God destroys the wisdom of the wise, as Isaiah [45:15] says, “Truly, thou art a God who hides yourself.”
So, also, in John 14[:8], where Philip spoke according to the theology of glory: “Show us the Father.” Christ forthwith set aside his flighty thought about seeking God elsewhere and led him to himself, saying, “Philip, he who has seen me has seen the Father” [John 14:9]. For this reason, true theology and recognition of God are in the crucified Christ. It is also stated in John 10[14:6]: “No one comes to the Father, but by me.” “I am the door” [John 10:9], and so forth.
21. A theologian of glory calls evil good and good evil. A theologian of the cross calls the thing what it actually is.
This is clear: He who does not know Christ does not know God hidden in suffering. Therefore he prefers works to suffering, glow to the cross, strength to weakness, wisdom to folly, and, in general, good to evil. These are the people whom the apostle calls “enemies of the cross of Christ” [Phil. 3:18], for they hate the cross and suffering and love works and the glory of works. Thus they call the good of the cross evil and the evil of a deed good. God can be found only in suffering and the cross, as has already been said. Therefore the friends of the cross say that the cross is good and works are evil, for through the cross works are destroyed and the old Adam, who is especially edified by works, is crucified. It is impossible for human beings not to be puffed up by their good works unless they have first been deflated and destroyed by suffering and evil until they know that they are worthless and that their works are not theirs, but God’s.
22. That wisdom which sees the invisible things of God in works as perceived by humans is completely puffed up, blinded, and hardened.
This has already been said. Because humans do not know the cross and hate it, they necessarily love the opposite, namely, wisdom, glory, power, and so on. Therefore they become increasingly blinded and hardened by such love, for desire cannot be satisfied by the acquisition of those things which it desires. Just as the love of money grows in proportion to the increase of the money itself, so the dropsy of the soul becomes thirstier the more it drinks, as the poet says: “The more water they drink, the more they thirst for it.” The same thought is expressed in Ecclesiastes 1[:8]: “The eye is not satisfied with seeing, nor the ear filled with hearing.” This holds true of all desires.
Thus also the desire for knowledge is not satisfied by the acquisition of wisdom but is stimulated that much more. Likewise the desire for glory is not satisfied by the acquisition of glory, nor is the desire to rule satisfied by power and authority, nor is the desire for praise satisfied by praise, and so on, as Christ shows in John 4[:13], where he says, “Everyone who drinks of this water will thirst again.”
The remedy for curing desire does not lie in satisfying it, but in extinguishing it. In other words, he who wishes to become wise does not seek wisdom by progressing toward it but becomes a fool by retrogressing into seeking folly. Likewise he who wishes to have much power, honor, pleasure, satisfaction in all things must flee rather than seek power, honor, pleasure, and satisfaction in all things. This is the wisdom which is folly to the world.
23. The law brings the wrath of God, kills, reviles, accuses, judges, and condemns everything that is not in Christ [Rom. 4:15].
Thus Galatians 3[:18] states, “Christ redeemed us from the curse of the law”; and: “For all who rely on works of the law are under the curse” [Gal. 3:10]; and Romans 4:: “For the law brings wrath”; and Romans 7[:10]: “The very commandment which promised life proved to be the death of me”; Romans 2[:12]: “All who have sinned without the law will also perish without law.” Therefore, those who boast that they are wise and learned in the law boast in their confusion, their damnation, the wrath of God, in death. As Romans 2[:23] puts it: “You who boast in the law.”
24. Yet that wisdom is not of itself evil, nor is the law to be evaded; but without the theology of the cross a person misuses the best in the worst manner.
Indeed the law is holy [Rom. 7:12], every gift of God good [1 Tim. 4:4], and everything that is created exceedingly good, as in Genesis 1[:31]. But, as stated above, the one who has not been brought low, reduced to nothing through the cross and suffering, takes credit for works and wisdom and does not give credit to God. Such a person thus misuses and defiles the gifts of God.
Those, however, who have been emptied [Cf. Phil. 2:7] through suffering no longer do works but know that God works and does all things in them. For this reason, whether they do works or not, it is all the same to them. They neither boast if they do good works, nor are they disturbed if God does not do good works through them. They know that it is sufficient if they suffer and are brought low by the cross in order to be annihilated all the more. Christ says this in John 3[:7], “You must be born anew.” To be born anew, one must consequently first die and then be raised up with the Son of Man. To die, I say, means to feel death at hand.
Luther certainly gives us much to chew on and digest here. The theology of the cross is not a theology about the cross (which can often be hijacked and turned into another form of a theology of glory!) but rather a theology through the cross, i.e. formulated from the perspective of Christ crucified as the locus of God’s saving power and revelation. For this reason, it is better, as indicated in the theses themselves, to speak rather of a theologian of the cross, for the theology of the cross simply indicates the point of view that we are forced to assume in relation to all reality on the basis of the scandal and folly of the gospel. The perspective of the cross stains things with the crimson color of blood and molds them into a cruciform shape. For this kind of theologian, the cross is more than a religious symbol or mere instrument of salvation, it is the lens through which the entire world is reinterpreted.
Thus, whereas the theologian of glory (i.e. everyone who is not a theologian of the cross!) looks for God in the likeliest places — i.e. where power, glory, and success are visibly seen — the theologian of the cross knows that God actually manifests himself in the unlikeliest and least expected places: in weakness, shame, and defeat. The theologian of glory measures according to standards of strength, greatness, and tangible results, whereas the theologian of the cross is attuned to the ignominy, smallness, and folly with which God reveals and redeems. This is, after all, is precisely what Paul argued in 1 Corinthians 1:20-29:
Where is the one who is wise? Where is the scribe? Where is the debater of this age? Has not God made foolish the wisdom of the world? For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach to save those who believe. For Jews demand signs and Greeks seek wisdom, but we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God. For the foolishness of God is wiser than men, and the weakness of God is stronger than men.
For consider your calling, brothers: not many of you were wise according to worldly standards, not many were powerful, not many were of noble birth. But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong; God chose what is low and despised in the world, even things that are not, to bring to nothing things that are, so that no human being might boast in the presence of God.
There are so many practical implications of this that it would be impossible to enumerate them all. Let me just suggest a couple. First, a theologian of glory can always be found prefacing statements with things like: “…but it doesn’t make sense that…”, “it seems logical that…”, “it’s unthinkable that God would…”, “surely if God had intended that, then…”, etc. To this the theologian of the cross will respond: “Yes, that does make more sense, and it does seem logical that God would act in such and such a way, but Christ crucified has put an end to all that makes logical sense to the worldly wise, and we can only seek to know the ways and works of God in the folly and scandal of the cross.” To use a biblical example, a theologian of glory stands at Golgotha and snides: “he who saved others could not save himself.” The theologian of the cross, on the other hand, looks at Christ crucified and marvels: “truly this is the Son of God!”
Second, a theologian of glory will become easily discouraged when effort is rewarded with failure, when faithfulness is rewarded with fruitlessness, when good is rewarded with suffering. A theologian of the cross, however, will remain unflappable and unmoved even when assailed by the fiercest doubts, even when experiencing the costliest losses, even when consigned to shame or anonymity. This, not because of an innate inner strength, but because the cross has taught its theologians to expect such outcomes. If the supreme display of the power and wisdom of God was the weakness and foolishness of Christ crucified, then we should not be surprised to find his power and wisdom displayed in our own lives in the exact same way.
Luther’s theology of the cross is a salutary reminder that whereas we are usually looking for God to come as a conquering king, we will only find him as a crucified carpenter. When this scandalous truth becomes the focal point through which we view all reality, then (and only then) we will begin to think, reason, pray, work, minister, and live as true followers of Christ.
 Martin Luther, Martin Luther’s Basic Theological Writings Third Edition. W. R. Russell & T. F. Lull, eds. (Minneapolis, MN: Fortress Press, 2012), 22-4.