This book looks at the Muslims in Mainland Tanzania, as well as what people in Southeast Tanzania understood by Islam, or by being Muslim, and what they sought to attain by becoming Muslim. This question may seem contrived: the personal reasons why a set of people, most of whom are now dead, changed their religious allegiance are unrecoverable. The most fundamental problem lies with the timing of the expansion of Islam. It is clearly shown that certain challenges and processes recurred over time in different guises.