[2] Patricia Crone later suggested that the book was “a graduate essay" and "a hypothesis," not "a conclusive finding.”[3] In his work Commanding Right and Forbidding Wrong in Islamic Thought (Cambridge, 2000), Michael Cook, in the chapter on the doctrine of al-Amr bi'l-Maʿrūf wa'l-Nahy ʿan il-Munkar among the Ibāḍīs, makes a comparison between western and eastern Ibāḍism and with the doctrines of the other Islamic sects and schools.

The eastern and western Ibāḍīs represent two distinct historical communities with largely separate literary heritages, at least until, roughly, the beginning of the twentieth century.

In Oman, the resilience of the Imamate down the centuries finds obvious and direct expression in the frequency with which the Omani sources link forbidding wrong with this institution.

In the West, where the vacuum left by the disappearance of the Imamate was filled in part by clerical organisation and authority, the scholars seem to have become less cautious about the role of the individual performer.

[4] Cook is also known for synthetic works for a general audience, including The Koran: A Very Short Introduction (Oxford, 2000) and A Brief History of the Human Race (Norton, 2003).

This six-volume project was selected as winner of the 2011 Waldo G. Leland Prize for the “most outstanding reference tool in the field of history” published between 1 May 2006, and 30 April 2011.