In "Othello," what does "Excellent wretch! Perdition catch my soul/ But I do love thee! And when I love thee not/ Chaos is come again" mean?
This quote is spoken in "Othello" Act III, Scene 3. It is spoken by Othello, the title character. When he says this line, he is speaking of Desdemona, his wife. What the quote means is that he loves her and he will always love her.
Perdition means "Hell." So he is saying that he will go to Hell if he does not love her ("but I do love thee" means "if I do not love you"). So he's saying "damn me if I ever do not love you (or if I ever stop loving you).
He then says that "chaos" will return if he does not love her, meaning that the whole world will fall apart, back to the way it was before God created it (the creation story in Genesis uses the word "chaos" for what there was before God started creating).
Othello expresses his deep love for Desdemona in this exclamation. The word "perdition," meaning Hell, comes from the Latin perdere ,which means "to put completely to destruction." He is therefore expressing that he loves her boundlessly, even to the point where his love for her threatens his own soul.
Throughout the play, there are many references to Hell and the Devil, incarnated in the character of Iago. He is able to manipulate Othello through his intense love of Desdemona, and indeed leads him and others to destruction by play's end.
In the quote above, Othello refers to his wife as an "excellent wretch." The reference appears to have been an affectionate one and does not evidence any malice towards Desdemona.
Later in the quote, we see the word "chaos," which is an interesting word. This is, in fact, what happens when Othello ceases to love Desdemona. Othello's words are prophetic here, and they foreshadow what his life will become as he descends into the madness of jealousy.
In fact, it is not long after Othello speaks these words that Iago begins to cast doubt in Othello's mind about Desdemona's loyalty. Essentially, Iago is the catalyst that causes "chaos" to erupt in Othello's life. The wily foe commences his scheme of destroying Othello by using subterfuge. He asks whether Cassio knew Desdemona when Othello was courting her.
The conversation that transpires between Othello and Iago shows how adept Iago is at manipulating his superior officer. Notice that Iago only implies evil on Cassio's part; he refrains from openly accusing Cassio of disloyalty. Iago knows in what esteem Othello still holds Cassio, and he treads carefully in order to avoid exposing his own motives. Iago stresses Cassio's honest nature while continuing to cast doubt on Cassio's character.
He uses dramatic pauses to suggest that he has some reservations about Cassio. Basically, Iago uses indirect expressions to manipulate Othello. Iago spends the rest of his time baiting Othello. He makes Othello beg to hear his thoughts about Cassio and Desdemona. Iago even warns Othello about jealousy in order to appear impartial. Throughout the entire conversation, Iago presents himself as a true friend whose only concern is for Othello's happiness. At this point, it's important to remember that Othello views Iago in the same light as the villain has cast himself.
It is Othello's implicit trust in Iago that leads to his downfall. Iago leaves Othello with a little advice. He suggests that Othello keep close watch on Desdemona and implies that, if Desdemona speaks out strongly about reinstating Cassio to his position, he will have all the proof he needs that Desdemona is having an affair with Cassio. So, this conversation between Iago and Othello in Act 3 Scene 3 is the catalyst that ushers in "chaos" into Othello's life.