It is my nature’s plague
To spy into abuses, and oft my jealousy
Shapes faults that are not.
– William Shakespeare
Othello, Act 3, Scene 3. After delivering a number of innuendoes about Cassio and Desdemona, Iago cunningly speaks of his own faults to Othello. This is so that he will appear more genuine and seem like an honest friend. Admitting to being a jealous person, he says that this makes him suspicious of everything and finding faults where they don’t exist. Iago is using psychological trickery to get Othello to trust him, one of the tools he employs to manipulate people. The phrase "nature’s plague" is a metaphor for jealousy.