 The third book deals with the crucial issue of the relationship between political and ecclesiastical authority. Dante argues on various grounds that power in the temporal realm is neither derived from nor dependent on spiritual authority, though it benefits from the power of the Papacy to bless its activity. These arguments consist largely in refutations of traditional claims for the temporal authority of the Papacy, but the final chapter makes the argument on positive grounds and in terms that recall the arguments first laid down in the Convivio. Since the human being consists of soul and body, its nature partakes of both the corruptible and the incorruptible. Uniting two natures, human existence must necessarily be ordered to the goals of both these natures [Mon. 3.16.7–9]: