The principal sources of Measure for Measure are George Whetstone's play of Promos and Cassandra (1578) and its prose redaction in the same author's Heeptameron Of Civil Discourses (1Sß2,). Whetstone's own source was Giraldi Cinthïo's Hecatommithi (1565) ; and Shakespeare almost certainly knew this work, which contains the story of Othello. He may, in addition, have also known Cinithïo's posthumously published play of Epitia (1583).

Brief summaries of these sources are given here for comparison with Shakespeare's treatment of the story.

Cinthio’s Hecatommithi, DECADE 8, NOVELLA 5

The Emperor Maximïan appoints one of his trusted men, Juriste, to rule over the city of Innsbruck. He

charges him particularly to observe justice scrupulously. Juriste, who lacks all self‑knowledge, accepts the grave responsibility with alacrity and for a while he is a model ruler.

A young man called Vico is brought before Juriste for violating a virgin, and is condemned to death according

to the laws of the city. Vico's sister, Epitia, who is a student of philosophy and has a sweet way of speaking,

pleads for her brother. Her brother is very young; he was moved by the impulse of love; the ravished maiden is unmarried and Vico is willing to marry her. The law was made so severe only to deter would‑be offenders, not really to be enforced. Captivated by Epïtia's beauty and eloquence, Juriste promises to reconsider the case. When she meets him again, he proposes that she should lie with him if she wants her brother's sentence to be mitigated. Epitia refuses unless Juriste is willing to marry her afterward. Juriste does not promise to do this, though he hints at the possibility. When Epitia goes to the prison to prepare her brother for his fate, Vico pleads passionately with her and appeals to her sisterly affection to save him. So Epitia reluctantly consents to Juriste's proposal. Juriste, however, orders the execution of Vico before lying with her.

Ì(n the morning Epitïa goes home to ffind that Juriste has indeed kept his promise to release her brother‑dead. She thinks of revenge, but instead appeals to the Emperor. The Emperor sends for Juriste and finds that the complaint is true. He (first forces Juriste to marry Epitïa, who is quite unwilling, and then he orders that Juriste be put to death. Now that Juriste is her husband, Epitia is in a cruel dilemma. She discourses to the Emperor on the superiority of clemency to justice. The Emperor is impressed with her forgiving nature and pardons Juriste. husband live happily ever after.

Cinthio’s Epitia

The story is much the same as that in the Hecatommithi, but there are some new characters and the brother is secretly saved by the captain of the prison. The latter announces this fact at the end of the play, to the astonishment of the other characters and also the reader, who is not given a hint of it in the prefatory "argument."

Principal among the new characters are Angela, Jurïste's sister, who conveys an offer of marriage from him to Epitia and testifies against him before the Emperor when Brother and sister argue, but finally Cassandra is won over.

After satisfying his desire, Promos decides to break his word, since no one knows of his promise and Cassandra cannot reveal her own shame. He orders that Andrugio should be executed secretly and his head sent to Cassandra. While the girl is eagerly looking forward to welcoming her brother, the jailer brings her the severed head. She conceals her grief, pretending to be quite satisfied. She thinks of suicide, but later decides to appeal to the Wig. The jailer has in fact brought her the head of an executed criminal and released Andrugio, who goes into hiding. Promos is secretly troubled at what he has done.

In the second part of the play, the King comes to Julio. He hears Cassandra's story and promises to see that justice is done. Upon examination, Promos at once confesses, and the King orders that he first be married to (Cassandra and then put to death. Promos pleads for mercy, but in vain. In the meantime, Andrugio, hiding in the woods, comes to know what is happening. Cassandra bewails her hard fate. Duty commands that she should love the husband for whose sentence she has been responsible. She appeals to the King to pardon him, but the ruler is adamant. Andrugio, now in the city under a disguise, sees his sister's unhappiness and resolves to surrender _ to the King at the risk of being put to death. Promos makes a sincere confession of his misdeeds and is led out to execution. Andrangio's boy enters with the news that his master is alive. The King pardons Andrugio, and then pardons Promos for the sake of Cassandra, exhorting Promos always to measure grace with justice. He restores him to the governorship of the city. "The lost sheep found, for joy the feast was made."

Whetstone's play has also a comic underplot, involving a courtesan, unscrupulous officers, informers, and bawds. With the corruption of the magistrates, all the city becomes corrupt.

The version in the Heptameron is substantially the same as that of the play. Andrugio is disguised as a hermit, and reveals himself after hearing the King say that Promos might be pardoned if Andnagio were alive. The entire story is narrated by one Isabella.

Summary

Measure for, Measure is generally closer to Whetstone's versions than to Epitia, but it does show significant correspondences will Cinthio's play at certain points where Whetstone differs markedly. "The relation of Measure for Measure to Giraldi's novella is ambiguous, since some of the correspondences to that might have come through Whetstone, some through Epitia. Among the similarities between Measure for Measure and Epitia may be mentioned the following: the secretary in Epttin protests to the podesta of the harshness of the law and the severity of its enforcement; in a, soliloquy he comments on the rigor of those in power (compare Escalus' protests to Angelo in II.i); the criminal whose head is substituted for that of Vico is hopelessly evil (compare Ragozine, described as a notorious pirate); like Isabella, Epitia also distinguishes between act and intention.