Luther detested the idea that God has established a law between Himself and His world, between Him and the finite actions and things and decisions. He wanted everything as non-rational, non-legal, as possible, not only in the process of salvation but also in the interpretation of history and nature; while Zwingli and Calvin accepted nature in terms of law. When therefore Immanuel Kant defined nature as a realm in which physical law is valid, this was much more Calvinistic or Zwinglian; in any case, it was not Lutheran. For Luther nature is the mask of God through which..He in an irrational. way very similar to the Book of Job acts when He acts with mankind.
Therefore the attitude toward nature in Calvinism and in Zwinglianism is much more according to the demands of bourgeois industrial society, namely to analyze and transform nature for human purposes; while Luther’s relationship to nature is much more in the sense of the presence of the Divine, irrationally, mystically, in everything that is. And if I hadn’t known this before, very theoretically, and not very safely, .I would have learned it when I came to this country.
For Zwingli the law of the Gospel is law not only, of course: he accepts Luther’s doctrine of the forgiveness of sins, as did every Reformer, naturally. But he at the same time spoke about a new evangelic law, as nominalists and humanists did. This law should be the basis of the law of the state. Don’t forget that Wyclif and Occam had exactly the same idea, and that in this point a more Catholic element is in the Reformed thinking, namely the thought that the Gospel can be interpreted as the new law. This term, the “new law,” is a very old one, appearing very early in Church history. For Luther, this would have been an abominable term; the Gospel for him is grace and nothing other than grace, and never can be the new law. But for Zwingli it can be. And this law is valid not only for the moral situation but also for the state, the political sphere. Politically, the law of the Gospel decides the laws of the city. If, therefore, cities do not subject themselves to the law, they may be attacked by those cities which’ subject themselves to the law; and the law is against Catholicism; so Zwingli started the war against the cantons in Switzerland, and died in the battle against them, and was conquered. But the principle remained, the principle that the law of the Gospel should be the basis of the state law, and this had tremendous influence in world history: it saved Protestantism from being overwhelmed politically by the Roman Church, by the CounterReformation.
But there is still one deeper element of difference between Luther and Zwingli. It is the doctrine of the sacraments. The fight between Luther and Zwingli in 1529 in Marburg was a fight between two types of religious experience one, of a mystical interpretation of the sacrament; the other, of an intellectual interpretation Zwingli said: The sacrament is a sure sign or seal reminding us as symbols, and expressing our will to belong to the Church. This: Divine Spirit sets beside them, not through them. Baptism is a kind of an obliging sign, like a. badge. It is a commanded symbol, but it has nothing to do with subjective faith and salvation, which are dependent on predestination.