The medieval Christian mystics have exerted a powerful influence on Christian spirituality, both Catholic and Protestant, that continues to the present day. Perhaps the most interesting example is that of Eckhart. Seventeen propositions in Eckhart's teaching were condemned as heretical by Pope John XXII in 1329, but this did not destroy his influence. During the fourteenth and fifteenth centuries, his writings continued to be copied and read in the Dominican and Carthusian Orders. He was known to the author of The Cloud of Unknowing, and his pupils Suso and Tauler continued to interpret his teachings in practical ways for the Christian life.

However, Eckhart's condemnation ensured that for several centuries his influence was far less than it might otherwise have been. In the early nineteenth century, interest in his writings was revived and scholarly German editions of his work were published. The twentieth century saw a remarkable...