In recent research, a much-needed insistence on religious diversity as a medieval phenomenon has come to the fore, and many studies have highlighted emerging concepts and practices of tolerance, pluralism and peaceful coexistence between religions during the Middle Ages. For all its advantages, however, this approach leaves out large segments of the medieval imagination – generally, the focus lies very firmly on inter-religious relations, even though many experiences of diversity within largely Christianized or Islamicized areas would have been intra-religious, i.e. experiences of diverging observances, religious orders, ‚sects‘ or other informal conventions shaping religious communities. Secondly, the decided emphasis on forms of pluralism foregoes to make use of a large and equally important area: An intriguing avenue towards evaluating medieval concepts of religious diversity may lie in analyzing polemics, invectives and scornful comparisons between religious groups. Typically studied for the light they throw on the image or stereotype of one specific group, such polemics have seldom been seen as (albeit negative) expressions of diversity.