Practitioners of takfir usually justify the doctrine by referencing the writings of one of Islam’s most revered legal theorists, Ahmad ibn Taymiyyah. Born in 1263 C.E, ibn Taymiyyah is widely acknowledged to be one of the greatest thinkers in Islamic history, a philosopher and theologian whose immense oeuvre—he wrote more than three hundred individual works—and famed piety led his disciples to give him the title of Shaykh al-Islam, an honor reserved only for the most supreme legal authorities.
