Othello is a complex character, first presented to the audience by Iago who gives an image of a man who is "loving his own pride and purposes" (I.i.12) and clearly cannot make a fair a decision, placing an "arithmetician...that never set a squadron in the field" (22) to be his lieutenant. The audience sympathises with Iago but is surprised at his apparent hatred and intention to "serve my turn upon him"(42), and his warning that "I am not what I am."(66)The audience is further led to question Othello's integrity on learning that he, "a lascivious Moor" (127) has married Desdemona.
Iago wastes no time in establishing his relationship with Othello who has no reason to doubt him. The one thing that Othello is confident of is his valor in battle and he knows that "my services which I have done the signory shall out-tongue his complaints." (I.ii.18-19)Othello seemingly plays to his strengths, such as his battle prowess and admits that "little of this great world can I speak"(86). This will be his undoing as, as a soldier, he sees value in reputation and anything dishonorable is inconceivable.
Othello is confident that Desdemona will confirm his love. His passion is evident and his commitment to everything he does is indisputable; even the Duke is enthralled - "I think this tale would win my daughter too."(I.iii.172) The audience then recognizes Othello's misplaced trust as he commits Desdemona to "honest Iago."(294) The audience has changed its perception of both Othello and Iago and can sees the trap being set which will unravel Othello and reveal his fatal flaw.
Circumstances serve to confuse Othello as Iago draws him into the belief that Desdemona could be anything less than pure.Iago intends to drive Othello into "a jealousy so strong" (II.i.295)having recognized a passionate man who is obviously susceptible. Iago ensures that Othello shows his disappointment of Cassio by demoting him after the brawl. Othello's perception is one-sided and he does not realise that appearances can be deceiving and is prepared to accept that Cassio has let him down and "unlace(d) your reputation." (II.iii.186) He may already be questioning his own better judgement, for having chosen Cassio. His trust in Iago is reinforced as "thy honesty and love" (239)is further entrenched.
As the play progresses and we see Iago draw Othello deeper into his trap, the audience understands that Othello and Desdemona are equally trusting and unquestioning. Desdemona does not see her own contribution to her demise. Othello is as much convincing himself of Desdemona's faithfulness as he is Iago when he says "She had eyes and chose me"(III.iii.192) but he is aware that "I am black"(267) and conversation is not his strong suit. He does get physical with Iago, demanding "ocular proof"(364) which of course Iago will deliver.
Othello is no match for Iago and by now is all but doomed. His fatal flaw, his jealousy has been unleashed and his trusting nature and confidence in "honest Iago," together with the doubt that, despite having "done the state some service"(V.ii.342) he is nothing more that a "turban'd Turk" (356)serve to seal his fate. Othello's misconception about honor "For nought I did in hate but all in honor" (298) and his value system, dependent only on his experience in war, are confirmed as he admits to being "one that loved not wisely but too well."(347) Speaking of himself in the third person and ultimately killing himself emphasize his conflicted state.