Brief authority
Isabella:
Merciful heaven,
Thou rather with thy sharp and sulphurous bolt
Splits the unwedgeable and gnarlèd oak
Than the soft myrtle; but man, proud man,
Dress'd in a little brief authority,
Most ignorant of what he's most assur'd—
His glassy essence—like an angry ape
Plays such fantastic tricks before high heaven
As makes the angels weep; who, with our spleens,
Would all themselves laugh mortal.
Isabella, a novice at the local convent, is pleading for her brother's life. Angelo, who's temporarily Vienna's chief executive, has got the idea into his head that it's up to him to reform the criminal justice system, and he begins by ruthlessly enforcing laws which had been ignored for years. One such law condemns fornicators to die, and Isabella's brother is the first victim. She has come to Angelo to beg for mercy—an essential quality of God's justice, as it ought thus be for man's justice.
As Angelo coldly refuses her entreaties, Isabella grows more passionate. She compares Heaven's tempering of its power to the cruel literalism of Angelo's justice. Heaven, when it strikes, at least strikes the most hardened and impassive victims—its thunder fells gnarled oaks, not soft myrtles. But Angelo, puffed up with pride by his "little brief authority"—his only temporary and limited power—arrogantly strikes out indiscriminately, even at soft myrtles like Isabella's young brother. Forgetting his "glassy essence"—the fragility of his soul, and its ultimate appointment with the Creator—arrogant man makes angels weep. If the angels had our "spleens" (self-regarding passions), they'd only laugh themselves to death.