The Duke of Vienna is the second major protagonist of Measure for Measure, and it is his apparent absence from the city that instigates the play’s action. At the beginning of the play, the Duke is a somewhat ineffectual leader. The city he rules is rampant with crime, and particularly the sinful crime of fornication. The brothel business is thriving in the urban center and the suburbs alike, and many of his citizens are getting pregnant outside of wedlock. He wants to do something about this situation, but he worries that he’d appear hypocritical were he suddenly to crack down on laws he’d previously neglected to enforce. Therefore, to clean up the city while keeping his own hands clean, he deputizes his authority to an unusually strict man named Angelo, whom he believes is eager to establish a reputation for himself by ridding Vienna of crime. Yet the Duke’s choice is also odd in the sense that he suspects Angelo of being perhaps too eager, which may result in chaos. His selection of a possibly inappropriate deputy is the first of several questionable decisions he will make in the play.

Although the Duke initially appears to us as a weak leader and a hypocrite, our perception of him changes when he disguises himself as a friar and becomes something of a spy in his own city. We see through his eyes how the citizens of Vienna view matters of crime and punishment. Some characters find Angelo’s desire to punish fornication pointless, since sex is natural and hence ineradicable. But even those who consider fornication sinful find Angelo’s prosecution of this unlawful act far too severe. Though the Duke initially resists this critique of Angelo, he’s swayed when he learns of Angelo’s sexual proposition to Isabella. From then on, the Duke commits himself to exposing Angelo’s hypocrisy and instituting a new moral order that takes a more balanced perspective on crime and punishment. A shrewd and seemingly omniscient planner, the disguised Duke orchestrates an elaborate plot that results in the grand performance that finally takes place in act 5. Although the Duke’s plotting involves several troubling acts of manipulation and deceit, his plan ultimately ensures that all crimes are punished with an appropriate balance of justice and mercy.