This article discusses Sheikh Muhammad Kasim Mazrui, an influential yet largely ignored figure within East African Islamic reformism, which shifted from internal to external domination in the second half of the 20th century. His educational booklet 'Hukumu za sharia', written in Kiswahili, is analysed and contextualised. Advising local Muslims, by way of clear argument and reference to authoritative texts, on how to deal with controversial local practices from an Islamic point of view, it pushed for the development of self-reliance, and criticised dependence on Islamic clerics and dignitaries. The text itself displays the rational principles that the reformist movement relied on and propagated, while it also contains hints of a more dogmatic tone that was yet to dominate reformist discourse. Overall, the article establishes a wider comparison in discussing this African Islamic reformism as an 'enlightenment' movement. The focus hereby is on structure rather than substance, as Islamic reform is incompatible with secularism. Common features, however, can be seen in the emphasis on rationality and self-reliance of individual actors, as well as the internal dialectic of the movements, oscillating between liberation and dogmatism.