In the preface, the authors said something very interesting
All three of us shared the conviction that contemporary theological issues and discussions in the Islamic world could not be understood by non-Muslims - or for that matter, Muslims - who were innocent of adequate knowledge of the theological disputes and schools that arose in the first five centuries of Islam. 
I couldn't agree more with the authors. Both the non-Muslims and Muslims don't understand the theological disputes among the Islamic schools (sects) that rose in the earliest days of Islam. To be honest, this is the main reason why I have a blog dedicated to researching the Islamic sects.
Nowadays, Muslims are very much focused on the activities of their own sects. Most Muslims no longer know anything about others. Sometimes you see and hear about Shia-Sunni Discourses, but that’s about it. It would be most unusual to see Muslims sitting down together and speak about all the other sects that branched out from the main body of Islam, especially during the first few hundred years.
 Martin, Richard C, Woodward, Mark R and Atmaja, Dwi S. 1997. Defenders of Reason In Islam: Mu'tazilism and Rational Theology from Medieval School to Modern Symbol. Oneworld Oxford. Preface. ISBN 978-1851681471