The epistle ascribed to Salim Ibn Dhakwan is a tract against 'wrong' doctrines regarding the classification and treatment of opponents. Written by an Ibadi before AD 800 and taking issue with both Kharijite extremists and Murji'ites, it was brought to the attention of Western Islamicists in the early 1970s by Amr Khalifa Ennami, and is here edited, translated, and discussed in full for the first time. The early centuries of Islamic religious thought have become a dynamic field in the last few years, and there is renewed interest in the attempt to use the early literature of the Muslim sects as windows onto the wider scene of doctrinal discussion in the period before the mainstream tradition becomes plentiful. In addition to making available a new source, this study seeks to open up the Ibadi tradition for future research on early Islamic thought, partly by making heavy use of Ibadi sources in its interpretation of Salim's epistle and by partly by offering systematic information about the Ibadi figures and literary works involved in the appendices and bibliography.