ance I assign my wife, With what else needful your good Grace shall think To be sent after me (I.iii.319-322).
Iago points out this flaw in Othello, with some irony, as he refers to Cassio:
You see this fellow that is gone before. . .
I fear the trust Othello puts him in On some odd time of his infirmity Will shake this island (II.iii.121,126-128).
Othello loses his faith in Desdemona, and he does so precisely because he has been so willing to trust everyone before this time. Iago notes whom Othello trusts, and then he finds ways to bring that trust into question, as he does with Cassio and as he does with Desdemona.
2. Othello is among the least reliable judge of Iago, for he believes him to be honest and refers to him as "Honest Iago" (as in I.iii.329). He trusts him to such a degree that he has him watch over his wife. Even after Iago's evil is exposed, Othello finds it hard to believe that any man, let alone one he has trusted, could do such things. Othello is not the only character to speak of Iago as "honest," however, and indeed this term is applied to Iago by nearly every other character. They all see him as an honest man and fail to perceive the way he manipulates them until the full nature of what he has done is exposed.
Iago's true character is perceived perhaps only by his wife, and she also does not see the depth of his perfidy until it is too late. Emilia allows herself to be manipulated by her husband when she gives him the handkerchief. She does not know why he wants it, but she surely understands that he is doing something he should not and that she is an accomplice. Indeed, though Emilia is not commenting directly on Iago, when she appears in the play she expresses a number of cynical observations on men. We can assume that she developed these anti-male ideas because of her experience with her husband.
Cassio and oth...