Paul Alvarus wrote the Indiculus luminosus in 854 in response to the executions of a number of Córdoban Christians, beginning with the monk Isaac in 851, who had denounced Muhammad in public. The first half of the treatise offers an extended apologia in defence of the militant actions of these spontaneous blasphemers. In the second half, Alvarus argues at length, on the basis of key passages in Daniel and Job, that Muhammad was a precursor to Antichrist. Alvarus undertook this exegetical project not only to create a context within which the actions of the Córdoban blasphemers would make sense, but to criticize the Córdoban Christian leadership at the time for being too cosy with the local Islamic rulers. While Alvarus relied on Jerome’s Commentary on Daniel and Gregory’s Moralia in Iob, he transcended them, offering a truly novel exegesis. In the process, he shed important light on the nature of Christian life under Islamic rule and demonstrated a surprisingly deep knowledge of Islam. The Indiculus luminosus is the perfect complement to the writings of his friend, Eulogius, who may in fact have encouraged Alvarus to undertake this task.