This essay offers an interpretation of Alfarabi's Book of Religion, in which the tenth-century philosopher addresses more directly than in any of his other works the relationship between human and divine wisdom. I argue that, despite his apparent silence about the orthodox view of divine law, Alfarabi's primary purpose in the work is to challenge precisely that view, along with the theological opinions on which it depends. To this end, the Book of Religion encourages the examination, by political science, of religion's claim to lead men to happiness. Previous scholarly work has not explored the extent to which the Book of Religion contains a confrontation with orthodoxy and is therefore unable to explain how Alfarabi justifies his thoroughly rational account of religion. Based on the interpretation presented here, Alfarabi comes to light as a philosopher open to the most fundamental alternatives, rather than a dogmatic rationalist.