Vincentio, Duke of Vienna. He leaves Vienna in Angelo's charge and returns disguised as Friar Lodowick to watch developments while incognito. Of some 2,600 lines in Measure for Measure, the duke speaks nearly 800, only slightly less than one-third. He acts as a deus ex machina to turn the play from tragedy to comedy. In his omnipresence, he has been compared to a puppeteer or divinity. The godlike disguised ruler was conventional to contemporary drama. Although he controls the other characters and their actions, the duke himself is very shallow of characterization. His purpose in leaving Vienna to his deputy and returning in disguise is unclear. He explains his motive to Friar Thomas as a wish to see long-ignored laws of morality enforced, without himself appearing as a tyrant. This implies a fatal weakness in him belied by his vigorous manipulations of the entire cast throughout the rest of the play, culminating in a dramatic confrontation of his own contriving. Angelo's critics suggest that the duke, sensing his hypocrisy, left him in charge to test him. Possibly he saw his deputy-and-disguise method as capable of making a dramatic issue of the moral decay of Vienna and the need for law and order, while at the same time emphasizing mercy and humanity. Finally, however, it must be confessed as possible, if not actually probable, that the duke had no logical, consistent reason for his action; perhaps he himself was a puppet of Shakespeare, who needed a device which would allow Isabella to give in to Angelo and yet maintain her virtue. The duke is manipulated by Shakespeare into a position whence he can manipulate the other characters.