Judgment
The central theme of Measure for Measure is judgment and justice, especially as it applies to those in power. The title of the play is taken from the Gospel of Matthew in an excerpt that warns against judging others too harshly, less one becomes the recipient of the same harsh judgment. The characters in Measure for Measure – especially Angelo, who condemns people to death for previously minor crimes – learn this lesson firsthand. The play also suggests that judgment and justice are not always the same, as Angelo's sentencing Claudio to death is clearly unjust given Angelo's own sexual transgressions throughout the play.
Deceit
There are a number of deception plots at work in Measure for Measure, the catalyzing one being the Duke's decision to yield power temporarily to Angelo while he disguises himself as a friar to secretly observe the political and social landscape of Vienna. While the Duke's deception appears relatively innocent, it is markedly self-indulgent as it leads to a number of conflicts while Angelo is in power, including the near-execution of Claudio. Angelo himself has the most malicious deceptive agenda, as he lies about his willingness to free Claudio and goes back on his word after what he thinks is a sexual tryst with Isabella. Finally, both the Duke and Isabella join together in a deception scheme to trick Angelo into marrying Mariana and to believing that Claudio was executed.
Political Corruption
At the beginning of the play, the Duke temporarily bestows his power upon Angelo as he (the Duke) allegedly must travel out of Vienna. The Duke notes that Vienna has experienced a decline in moral piety under his rule due to his laissez-faire enforcement of the law, and he gives Angelo the power to decide which laws to enforce and to what extent. Angelo takes advantage of this newfound power by moving toward the other extreme of the political spectrum – he judges others harshly and deals out death sentences for minor crimes. The difference between the two governing strategies of the Duke and Angelo suggests that unchecked power inevitably leads to political corruption.
Mortality
Throughout the play, many characters contemplate death and mortality. Of course, the most apparent example of this theme is Claudio, who for most of the play is set to be executed after it is discovered that his betrothed, Juliet, is pregnant before they are married. In what some consider one of the most eloquent speeches in all of Shakespeare's plays, Claudio ruminates on the different incarnations of death, what it looks like, and whether the uncertainty of death is preferable to suffering on earth. Many believe that this speech was a precursor to the famous "To be or not to be" soliloquy from Shakespeare's Hamlet, another play whose characters are veritably obsessed with death and dying. That this preoccupation with mortality appears in a comedy has led many to identify Measure for Measure as a genre-blending performance with both comic and tragic elements at work.
Sex
Sex is an important theme in the play, as it often dictates certain characters' actions and motivations. Claudio is sentenced to death for fornication – or sex before marriage – when it is discovered that Juliet is pregnant. Then, when Isabella pleads to Angelo to spare Claudio's life, Angelo propositions Isabella for sex in exchange for Claudio's freedom. Isabella is horrified and almost immediately chooses her own chastity over her brother's freedom, comparing sex to death itself as she imagines she will be eternally damned if she accepts Angelo's proposition. In this way, sex serves as both a major plot device and a major source of anxiety throughout the play, as it becomes something that must be kept secret due to the new government's staunch policing of citizens' sexual behavior.
Hypocrisy
Along with the theme of political corruption comes the theme of hypocrisy (a common theme in early modern English comedies). The shining example of hypocrisy in the play is Angelo, who happily engages in the same "crimes" for which he has sentenced Claudio to death: Claudio is punished for fornication (or sex before marriage), but when Isabella pleads with Angelo to spare her brother's life, Angelo propositions Isabella for sex. Thus, not only is Angelo a harsh leader, but he is also a hypocritical one who takes advantage of the very law he purports to enforce.
Marriage
One of the tell-tale ways to identify an early modern comedy is to determine whether the play ends with one or more marriages. Measure for Measure subscribes to this convention, but it also presents a much more cynical look at marriage than other Shakespearean plays. For some characters – like Lucio – marriage is the equivalent of a miserable life. For others, it is likened to a death sentence. Furthermore, in one of the most ambiguous moments in the play, Isabella is silent when the Duke proposes marriage. This notable silence prompts the audience to question whether marriage (normally seen as the ultimate theatrical form of resolution) is truly the answer to conflict and the path to happiness.