The great Luther scholar Paul Althaus once referred to Luther as an “ocean.” This word can be used both for Luther’s enormous literary output (over one hundred folio volumes—each more than one foot high—in the German edition of his Works) and his originality. Only a handful of theologians in the history of Christian thought approach his stature—perhaps Augustine, Thomas Aquinas, Edwards and Barth.

Eyewitnesses recounted that whoever spoke to Luther was riveted by the intensity of his eyes. After his interview with Luther in August 1518, Cardinal Cajetan spoke of the monk with the strange eyes. A Swiss student in Wittenberg described Luther’s eyes as “deep, black, blinking, and glittering like a star.”

Luther was of medium build and had a good sense of humor—often crude, always robust. For instance, at the end of his life he promised, “When I get home to Wittenberg again, I will lie down in my coffin and give the worms a fat doctor to feast on.” But he wasn’t always fat. When he left the monastery in his mid-thirties, he had fought the flesh so long that a friend said he was “haggard from worrying and studying, so that one can almost count his bones through the skin.”

Luther was an emotional man. He had a temperament like a volcano that could explode at any moment. Yet a contemporary said he had a clear and articulate voice, and was usually courteous, even cheerful. But “he criticizes a bit too caustically and aggressively.” While his tendency to criticize was not unusual for his age, it reflects a huge personality who was completely down to earth—at the same time full of humor and occasionally foul-mouthed. If you have ever thought theology makes for dull reading, you have not read Luther. Try his Table Talk (notes made by his theological students on his remarks over meals) for starters. Here’s a typical statement by this “hearty” theologian: “If our God makes excellent large pike and good Rhine wine, I may very well venture to eat and drink [them]! You may enjoy every pleasure in the world that is not sinful; your God doesn’t forbid it, but rather wills it. And it pleases God whenever you laugh from the bottom of your heart.”

Luther was rarely at a loss for confidence. While scholars often wrote ni fallor (If I am not mistaken), Luther wrote immo (certainly!). Perhaps because of this self-confidence, he wrote so much that sometimes scholars complain you can find anything you want in his writings, and occasionally differing opinions on the same subject. Of this intellectual restlessness Luther said about himself, “They are trying to make of me a fixed star. I am not—I am a wandering planet.” The result is that in his gargantuan writings, there is plenty of nearly everything, which means that reading Luther can be like panning for gold—there are dross and waste, but also precious nuggets of pure gold.

The German reformer loved nature. Throughout the great Leipzig disputation he was wearing a silver ring, with an amulet against evil, and holding a flower, occasionally smelling it. He loved to relax in a garden, and, “in defiance of the devil” delighted in flowers, especially roses, as God’s gift.

Luther’s cardinal insight was justification by grace through faith alone. He called it “the summary of all Christian doctrine.” As a Catholic monk the phrase in the Latin version of Rom 1:17 (“in the gospel the righteousness of God is revealed”) struck terror into his soul. He thought “righteousness” (iustitia was the word in Luther’s Latin Bible) meant God’s active punishment of sin (what we would call justice), and feared that his attempts to avoid that punishment were not enough. He had prayed for hours on end, fasted until he looked emaciated, kept vigils, and performed good works—but he still had a guilty conscience. His mood swung from despair over his own failures to a simmering rage at God: “I did not love, yes, I hated, the righteous God who punishes sinners, and secretly, if not blasphemously, certainly murmuring greatly, I was angry with God.”

But Luther kept reading Paul, desperate for relief and guidance. He says he meditated on Paul night and day, until finally he saw the light.

I began to understand that the righteousness of God is that by which the righteous live by a gift of God, namely by faith. And this is the meaning: the righteousness of God is revealed by the gospel, namely, the passive righteousness with which merciful [sic] God justifies us by faith, as it is written: “He who through faith is just shall live” [Hab 2:4]. Here I felt that I was altogether born again and had entered [paradise itself through open gates.”

The year was 1519. Luther was thirty-five.

What had driven Luther to such torment? Why was he, an Augustinian monk, unable to see the grace of God which Augustine had taught?

There were three reasons.

The first problem was the doctrine of divinization which we have seen in Athanasius and Augustine. Athanasius said God made man so that man could become a god. Augustine said we share this divine nature by participating in the sacraments. The implication, as this doctrine became hardened in the Middle Ages, was that we are accepted as righteous (in Luther’s Latin translation, “just”) by God only after we have become righteous by the infusion of God’s nature. The question that tormented Luther was, What if I don’t sense this divine nature within me? Am I perhaps trusting an idol?

The 4th Lateran Council (1215) had pronounced that only sins confessed to a priest could be forgiven. This drove a conscientious soul like Luther absolutely frantic. He was obsessed with the fear that he might have overlooked one sin. He would spend hours in the confessional with his spiritual director Staupitz, walk away, and then come rushing back because he had remembered another little foible.Staupitz was exasperated. “Look here, brother Martin. If you’re going to confess so much, why don’t you go do something worth confessing? Kill your mother or father! Commit adultery! Quit coming in here with such peccadillos!” Then Luther had another doubt. Was he really sorry for his sin, or just afraid of hell? At this point he was driven to the depths of despair, so that he wished he had never been born. He turned from hating himself to hating God for making him, and for making justification seem impossible.

The 15th-century German theologian Gabriel Biel had taught that God will give grace only to those who try their best. This was much like our American saying today, “God helps those who help themselves.” The assumption was that God’s grace is based on what we do. He gives it only to those who are trying their hardest. But again, Luther, with his sensitive conscience, always wondered if he was doing his best. How could he know, since he also knew that the human heart is “devious above all else” (Jer 17:9)? Maybe he thought he was trying his best, and his heart actually was tricking him, camouflaging his half-heartedness. How could he know for sure?

The breakthrough came when he saw, from Paul’s epistles and Paul’s own life story, that what precedes grace is not great effort but in fact active rebellion. As Paul put it in Romans 5:6, “Christ died for the ungodly”—not the godly. Paul didn’t find grace while trying his hardest to serve Christ. Quite the opposite: he found grace when trying to kill Christ! He was on his way to Damascus to arrest Christians and deliver them over to punishment and possible death. And Jesus said that as he was trying to kill Christians, he was really after Christ himself: “I am Jesus whom you are persecuting” (Ac 9:5).

Luther felt liberated. He felt like he had been born again. God was not looking for religious and moral perfection before he would bestow grace. Instead he joined people to Christ when they were even fighting against him—and not because of their goodness but in spite of their badness. The only stipulation was that they believe that it was Christ’s works and not their own that had brought them to God.

Protestantism was born. And out of this seminal insight—not radically new but now renewed—evangelicalism came to birth three hundred years later.

Gerald McDermott blogs on the Patheos Evangelical channel at The Northampton Seminar.