This paper deals with the relation between Nicholas of Cusa and the Dutch philosopher Heymericus de Campo. Nicholas is celebrated for his rather positive attitude towards Islam. In De pace fidei (1453) he presents the vision of una religio in rituum varietate and in his Cribratio Alkorani (1460/61) Nicholas tries to prove Christian dogmas on the basis of the Koran. This idea he had discussed with his Dutch friend several decades earlier. In his Disputatio de potestate ecclesiastica (1433/34) Heymeric scrutinizes the question, whether the highest authority in the church belongs to the pope or the council, on the basis of the Koran. He presents ten arguments in favour of the council and one in favour of the pope. This shows that Nicholas developed parts of his exceptional thought in conversation with Heymeric and suggests that a closer examination of Heymeric's texts will reveal a new side of the young Cusanus.