It would be interesting to survey members of the Presbyterian Church as to what they thought was Martin Luther’s most significant insight into theology. Most would probably identify his doctrine of justification by faith alone — the truth that inspired him to hammer his Ninety-Five theses onto the cathedral door in Wittenberg in 1517.

However, one year later, at a rather low-profile gathering of Augustinian monks called the Heidelberg disputation, Luther unveiled what Alistair McGrath has described as “one of the most powerful and radical understandings of the nature of Christian theology which the Church has ever known”. I am referring, of course, to Luther’s theology of the cross.

What is this “theology of the cross”? Luther knew that many people were medi­tating on the death of Jesus in order to pro­duce sentimental sorrow for him, not a sor­row for their own sins which put him there. Essentially, it became his belief that the cross holds the key to understanding the character of God and the nature of the Christian life. Luther expressed this con­viction in a number of pithy statements, such as: “the cross alone is our theology,” “without a theology of the cross, man mis­uses the best things in the worst way,” “true theology and knowledge of God are in the crucified Christ,” and “the cross puts everything to the test”.

Central to Luther’s understanding of the theology of the cross was his belief that the cross was not only the means by which we are saved, but it was also the means by which we know God. Let me explain. As Luther thought long and hard about the way we may come to know God, he realised that the apostle Paul was pointing to the cross as the key which opened up the mystery of God’s character.

But how? As Luther reflected on Paul’s first letter to the Corinthians, he was struck by the fact that “the message of the cross” (1:18) was a completely new and unexpect­ed way of knowing God. Other methods, such as philosophy or spectacular signs, hadn’t succeeded. The world’s ways of try­ing to know God had ironically resulted in a not-knowing. But “the message of the cross” was God’s way of revealing Himself, despite the fact that ideas of “Messiah” and “crucifixion” seemed mutually contradictory.

So how does God reveal Himself at the cross? In Thesis 20 of the Heidelberg Disputation, Luther tells us that when we look at the cross and Christ’s sufferings, we get a glimpse of God in the same way as Moses did (Exod. 33:23). While common sense might suggest that we could learn more about God from the silent beauty of a snow-capped mountain or a golden sunset, the cross tells us that God reveals Himself in a way that is totally unexpected and which the world rejects as madness.

While reason may be a useful tool in many areas of human inquiry, when it comes to the knowledge of God, it is sim­ply unreliable (1 Cor. 1:21). God has mocked the world’s wisdom by revealing His glory in the shame of an execution. He shows Himself in lowliness and humility. There are several lessons from this.

First, this means that we don’t know God through watching the stars or reading crystals or hugging trees in the forest! We know Him because in the death of Jesus we see God’s Son dying at the hands of sinful men. In a seemingly foolish way, God showed the greatness of his power by doing the unthinkable and dying on the cross. This is a reminder to us of the limitations of our reason in doing theology. The cross teaches us to accept God as He reveals Himself, and not to refashion Him in a way that fits more easily with what we think is reasonable. God explodes our ideas of what is normal and rational for deity.

Second, the theology of the cross is a warning to us not to put too much store on our own experience. We often meet people today who interpret everything in the light of personal experience. When they reject Christian truth, they will often say: “That might be all right for you to believe, but I can’t say that I’ve ever felt that way.” Experience is all that matters to them.

But consider this: did anyone among the disciples on Good Friday feel that God was powerfully pre­sent in the crucifixion? Wasn’t the opposite the case? Didn’t the disciples flee because they felt abandoned and helpless? Yet in the light of the resurrection, we know that while God was hidden in the tragedy of Calvary, He was still present and active. But not every disciple saw this. Thomas particularly, was liv­ing by his feelings on Good Friday rather than his faith in God’s promises. He made the painful dis­covery on Easter Sunday that feelings are a very unreliable guide to truth. We may not feel God’s presence, but that doesn’t mean He is not with us. We have to come with empty hands to the foot of the cross for it’s in that way we come to know God and find the reality of sins forgiven.

Third, what happened to Jesus on the cross helps us understand our own life of suffering. Believing in Jesus does not exempt us from pain and distress. We are called not only to believe in Jesus but also to suf­fer for him (Phil. 1:29). The pattern that Jesus sets his disciples is one of humiliation and then exalta­tion (Phil. 2:1-11). The norm for a true Christian experience is one of suffering. This is an important insight of the theology of the cross. When Paul says that “we always carry around in our body the death of Jesus” (2 Cor. 4:10), he is reminding us that suf­fering rather than health or wealth is a sign of God’s presence and blessing. The cross calls us, not to a smooth and trouble-free life, but to one of pain.

Finally, the theology of the cross has to be applied to all of church life today. One of the characteristics of our age, even in the church, is a strong belief in personal rights and the practice of individualism. People look at themselves as customers who have a right to be indulged and satisfied. But the cross is a direct challenge to everyone who sees Christianity as a “what’s-in-it for me?” religion. The cross pro­claims that you gain life by losing it. This does not sit comfortably with self-interested religious con­sumers. Nevertheless, it is true.

Where do we begin the search for spiritual renewal in the Presbyterian Church of Australia? I think Mark Noll, the American church historian, points us in the right direction when he says: “Ultimately, the greatest hope for evangelical thought lies with the heart of the evangelical mes­sage concerning the cross of Christ.” In trying to understand what this means for us, we can select no better guide than Martin Luther to help us appreci­ate the vast dimensions of the cross of Jesus.