Luther’s Theology of the Cross by Alister E McGrath is a book that combines excellent historical work with a style and substance that will give the reader a deeper understanding of Luther’s theology of justification by faith alone and its related doctrinal issues. The readers should be aware that this is first and foremost a thoroughly historical work. The author leaves many Latin and German words and phrases untranslated. This should not be too much of a hurdle as the learning from this book makes it worth it to persevere.

If the reader loves the doctrine of justification by faith alone, then he or she will love this book. Luther’s theology of the cross is connected to his understanding of justification. The justified sinner sees in the cross of Christ the blazing glory of God, while the world is blind to it. The glory of God is thus hidden to the world because the world expects to see a different kind of glory. The justified sinner is one who with humility receives by faith the glorious righteousness of Christ given to him through Christ’s work on the cross.

Luther’s theology of the cross is perhaps one of his lesser-known doctrinal distinctives. We have all heard about Luther’s theology of justification by faith alone in Christ alone, which was based on his understanding of the righteousness of God. In the same manner, Luther’s understanding of the theology of the cross organically flows from his understanding of the righteousness of God. In this book, the author, Alister E McGrath, paints a picture of the context in which Luther’s understanding of the righteousness of God developed.

It's quite easy to assume that when Luther nailed his 95 theses on the door of the church at Wittenberg, Germany he had fully developed his understanding of the doctrine of Justification by faith alone. McGrath, through careful historical research and presentation, shows us that Luther’s understanding of Justification by faith alone developed over time.

McGrath observes that Luther’s own understanding of justification in the earlier stages of his theological exploration was influenced by the late medieval understanding of justification. The Latin phrase which captures the medieval understanding of justification is “Facientibus quod in se est Deus non denegat gratiam” which means that God will not deny grace to those who do their best or to those who do what lies within them.

According to this understanding, God will count our sincerest and best efforts (although still sinful to a certain extent) as our righteousness on the basis of which he justifies us. This understanding stemmed from the fact that none of us is actually righteous before God according to his absolute standard of holiness. Therefore, God must accept something apart from perfect righteousness as the basis on which he must justify us.

The medieval theologians proposed that our sincerest and best efforts must suffice, but Luther understood that humility, which recognizes our own unrighteousness, and faith, which receives the righteousness of Christ, serves as the basis on which God justifies the ungodly.

Thus, Luther’s theology of the cross reveals the heart of the justified sinner. There is no other way apart from humility and faith in Christ that one is justified before a holy and righteous God. Luther discovered that the righteousness of God in respect to the justified sinner is not one that condemns him, but one that declares him righteous by providing the righteousness of Christ through his death and resurrection.

The cross may seem like folly to the unbelieving world, but to us who are being saved, it is the power of God for salvation (Rom 1:16). Soli Deo Gloria!