Karl Barth’s Göttingen lecture on Zwingli from 1922/23 is a must-read. It is not only an excellent – though fragmentary – introduction to Zwingli – and Luther as well, especially concerning the debate on the Eucharist, but it also reveals much of Barth’s fundamental understanding of theology: as humans we do not own the truth, we can only search for it. As Barth said much later in his Bonn lecture on the Heidelberg Catechism of 1948: "We do not possess the Gospel of Jesus Christ as a dead good. We must beware of a capitalistic understanding of Christianity.