Context: The Duke of Vienna pretends a trip to Poland, turning over the reins of government to Angelo, deputy of the duke, with orders to enforce the laws against unchastity. Claudio, a young gentleman, is immediately sentenced to death for breaking these laws. Claudio sends his sister, Isabella, who is about to enter a cloister, to Angelo to plead for his life. Angelo refuses Isabella's pleas; but he is passionately aroused by her beauty, and he offers to save her brother's life if she will yield herself to him. Indignantly, Isabella says that Angelo must give her brother a pardon, or she will proclaim his hypocrisy. Shakespeare uses an expression similar to Isabella's–"Let me tell the world"–in King Henry IV, Part I (Act V, sc. ii, l. 65). Robert Browning also uses a similar one: "Ay, tell the world!" in Paracelsus, Part II, (1835). The expression from Measure for Measure is a widespread asseveration today, often coupled with adjectives, as: "I'll tell the cockeyed world." Isabella's expression, in context, is different from the colloquial American usage:
. . .
I will proclaim thee Angelo; look for't.
Sign me a present pardon for my brother,
Or with an outstretched throat I'll tell the world aloud
What man thou art.