How do Cassio’s and Iago’s opinions about the importance of one’s reputation differ?

Cassio laments that he has lost his reputation, which is very dear to him. Iago tries to convince him that a reputation means little.

Iago and Cassio are juxtaposed in this scene, to bring out Cassio's flawed honor and courtliness, and Iago's manipulativeness and deceptiveness. Cassio stands in especially sharp contrast to Iago when Iago speaks lustfully of Desdemona; Cassio is full of honor when it comes to women, and the ideals of a courtier as well. "He's a soldier fit to stand by Caesar," Iago says, the allusion to Caesar betraying the fact that he knows Cassio's true quality. However, Iago strikes gold when he figures out Cassio's weakness for drink; it is this flaw that makes Cassio finally seem human, and tarnishes his golden, polished image. "He'll be as full of quarrel and offense as my young mistress' dog," Iago notes; his metaphor shows that he knows how liquor can separate even the best man from himself, and do great damage to his reputation. "His vice Œtis to his virtue an equinox, one as long as th' other," Iago states; Iago's metaphor again reinforces his perceptiveness, and the light/dark imagery in the metaphor continue a motif present throughout the play.