"By the Pure Grace of God Alone"

From Benjamin Warfield, "The Theology of the Reformation"
What happened at the Reformation, by means of which the forces of life were set at work through the seething, struggling mass, was the revival of vital Christianity; and this is the vera causa of all that has come out of that great revolution, in all departments of life. Men, no doubt, had long been longing and seeking after "a return of Christianity to something like primitive purity and simplicity." This was the way that an Erasmus, for example, pictured to himself the needs of his time. The difficulty was that, rather repelled by the Christianity they knew than attracted by Christianity in its primitive purity - of the true nature of which they really had no idea - they were simply feeling out in the dark. What Luther did was to rediscover vital Christianity and to give it afresh to the world. To do this was to put the spark to the train. We are feeling the explosion yet.

The Reformation was then - we insist upon it - precisely the substitution of one set of theological doctrines for another. That is what it was to Luther; and that is what, through Luther, it has been to the Christian world. Exactly what Luther did was for himself - for the quieting of his aroused conscience and the healing of his deepened sense of sin - to rediscover the great fact, the greatest of all the great facts of which sinful man can ever become aware, that salvation is by the pure grace of God alone.