In Friar Lawrence's opening soliloquy/monologue of Act II, Scene 3, he presents his philosophy of life. The speech is a soliloquy in the first 22 lines as he is alone on stage, and from lines 24-31 it is considered a monologue because Romeo has appeared on stage and the Friar is speaking to him.
The Friar believes that within the earth "resides" both good and bad elements. One single flower may contain both poison and medicine. The earth is both a womb and a tomb as it produces life and then lets it die. Even the worst poisonous plant provides something positive for the earth. And elements that are essentially good can also wind up doing great harm.
He compares this to humans. Even the worst person may have something positive to contribute. Likewise, a basically good person can commit an evil act. He says,
Within the infant rind of this weak flower
Poison hath residence and medicine power:
For this, being smelt, with that part cheers each
Being tasted, stays all senses with the heart.
Two such opposèd kings encamp them still
In man as well as herbs—grace and rude will;
And where the worser is predominant,
Full soon the canker death eats up that plant.
This theme of good and evil pervades the play. Good people commit foolish and evil acts. Mercutio
and Tybalt are quick-tempered and belligerent, but we know they have good in them. Mercutio is Romeo's closest friend and confidant. Tybalt is also loved by his family, especially the Nurse, who takes his death badly. Lord Capulet
adores his daughter (see Act I, Scene 2
) but is at least partly responsible for her eventual suicide after his tirade at the end of Act III. Friar Lawrence himself contributes to the bad karma as he too could be considered responsible for the suicides after he devises the plan involving Juliet faking her death. Romeo carries out an evil act when he kills Paris
at Juliet's tomb in Act V. Juliet is one character who doesn't display an evil side, yet she is the victim of the foolish acts that surround her.