While in the West the idea of the Caliphate evokes overwhelmingly negative images, throughout Islamic history it has been regarded as the ideal Islamic polity. In the wake of the Arab Spring, and the removal of long-standing dictators in the Middle East whereupon the dominant discourse appears to be one of the compatibility of Islam and democracy discussion about reviving the Caliphate has continued to exercise the minds of its opponents and advocates alike. Reza Pankhurst's book contributes to our understanding of Islam in politics, the path of Islamic revival across the last century, and how the popularity of the Caliphate in Muslim discourse waned and later re-emerged. A comparative analysis highlights the core commonalities as well as differences between the various movements and individuals. Pankhurst shows why, as movements struggle to reestablish a polity which expresses the unity of the ummah (global Islamic community), the Caliphate has alternatively been ignored, reclaimed and promoted as a theory and symbol in different ways, or had its significance minimised and denied, yet continues to serve as a political ideal for many.