(Evangelical Church in Germany (EKD) head Bishop Nikolaus Schneider (L) walks to the cloister with Pope Benedict XVI in the Augustinian Monestry (Augustinierkloster) in Erfurt September 23, 2011/Max Rossi_

Pope Benedict, visiting the German monastery where Martin Luther lived before launching the Reformation, warned his Lutheran hosts on Friday that what he called “a new form of Christianity” posed a challenge to mainline Protestants and Catholics alike. While not naming them, it was clear that the pope, whose visit to this small city south of Berlin was sparsely attended, was referring to the evangelical and Pentecostal churches which have been attracting converts from more established churches, especially in Third World countries.

“Faced with a new form of Christianity, which is spreading with overpowering missionary dynamism, sometimes in frightening ways, the mainstream Christian denominations often seem at a loss,” the pope said on the second day of his third trip to his homeland as pontiff. “This is a form of Christianity with little institutional depth, little rationality and even less dogmatic content, and with little stability. This worldwide phenomenon poses a question to us all: what is this new form of Christianity saying to us, for better and for worse?”

Benedict appealed for unity between Roman Catholics and Protestants, who began their split from the church in the 16th century with the posting by Luther, who lived in Erfurt as a Catholic monk, of his 95 Theses in 1517.

At the same time, he deflected appeals from Protestants for a relaxation of rules barring them from participating in Catholic communion.