Horses
Horses are an important motif in the play. References to horses appear early on, when Duke Vincentio tells Angelo that he has been too laid back about law enforcement in Vienna and the citizens have therefore become stubborn "horses" who must be reigned in. Horses, therefore, come to represent the power dynamic between a ruler and their subjects, with some believing that citizens must be "tamed" into submission and others – like the Duke – allowing the population to essentially run free without consequences.
Coins
References to coining abound in the play, typically as a metaphor for reproduction. This was not an uncommon comparison in early modern English literature, where children were often described as being "stamped" or "imprinted" by their parents. The numerous references to coins are therefore often associated the legitimacy of one's offspring, with counterfeit "coins" being illegitimate children.
Character Substitutions
Measure for Measure features a number of important substitutions that drive the plot. First, the Duke substitutes Angelo for himself as leader of Vienna, leading to the central conflicts of the play. Second, Mariana is substituted for Isabella during the "bed trick" that she and the Duke arrange for Angelo, and later Ragusine's head is substituted for Claudio's in the "head trick" of Claudio's execution. All these substitutions become self-referential allusions to the theater itself, where actors are in fact "substitutes" for actual people.
The Bible
The Christian Bible appears again and again throughout the play, and becomes the central referent for Angelo's judgements while also serving as Isabella's guiding principle as she decides whether to save her brother's life. Even the title of the play comes from a biblical passage from the gospel of Matthew: "Judge not, that ye be not judged. For with that judgment ye judge, ye shall be judged: and with what measure you meet, it shall be measured unto you again" (Matthew 7:1-2). This passage argues for refraining from judgment that one would not want to experience themself, a distinct lesson learned by unfair "judges" like Angelo.
Brothels
Both Mistress Overdone and Pompey are responsible for running brothels in the play, which appear quite prevalently on the streets of Vienna. The numerous references to brothels suggests that, under the governance of Duke Vincentio, the city's moral character has begun to decline. Angelo outlaws brothels and has them torn down, but this does not necessarily signify the restoration of ethics to the city. On the contrary, after the brothels are destroyed, Pompey becomes an executioner, suggesting that the obliteration of one kind of sin (fornication) is simply replaced by another (murder).
