Muslim medieval authors were fascinated with religious issues, as the corpus of Arabic literature clearly shows. They were extremely curious about other religions and made intense efforts to describe and understand them. A special brand of Arabic literature—the Milal wa-Niḥal (“Religions and Sects”) heresiographies—dealt extensively with different sects and theological groups within Islam as well as with other religions and denominations: pagan, Zoroastrian, Jewish, Christian, Hindu, and others. Of course, most of the heresiographies were written in a polemical tone (sometimes a harsh one, like that of the eleventh-century Spaniard Ibn Ḥazm's: Al-Faṣl fi-l-Milal wa-l-Ahwā wa-l-Niḥal [“Discerning between Religions, Ideologies, and Sects”]), but some come close to being objective, scholarly descriptions of other religions (for example, Al-Shahrastānī's Milal wa-Niḥal book from the twelfth century).