 Whatever the precise nature of the dilemma to which Dante alludes, the fourth treatise is marked by a noticeable shift away from metaphysics in the direction of ethics and rhetoric. Philosophical knowledge is redirected to the purposes of social and political life, and the treatise, while punctuated like the others by numerous digressions, pursues a single sustained argument. Dante begins by explaining that social order is a necessary condition for human happiness and that it requires a single governor whose authority embraces that of all particular governors and directs their several efforts to a single end [4.4]. After a long digression on the role of Rome in the providential design of human history, he turns from political to philosophical authority, citing Aristotle as in effect the governor of the mind, “master and guide of human reason insofar as it is occupied with its final end” [4.6.8]. From this, Dante derives the conclusion that even an emperor’s authority must be circumscribed insofar as the art of ruling and the laws it creates cannot overrule rational judgment based on the laws of nature [4.9].