The principal method that Iago uses to convince Othello of Desdemona´s infidelity is by using one of Othello´s most treasured possessions and telling Othello that his wife, Desdemona has given it away to her lover, Cassio. This treasured possession of Othello´s is a handkerchief, which “Did an Egyptian to my mother give”. The handkerchief is important to Othello because it is a link back to his mother who also told Othello to give it to his wife. “She dying gave it me, And bid me when my fate would have me wive, To give it her”. So to Othello this handkerchief is very important, especially as he describes it as having “magic in the web of it”. It was also the first gift he gave to Desdemona, so this handkerchief is of enormous sentimental value to Othello. Finding out that Desdemona has given it away without a care for him, would almost certainly anger him, for in Othello´s mind she has thought the handkerchief to be a meaningless piece of cloth. Iago tells Othello that he saw Cassio wiping his mouth with it, much like a rag. “ I know not that; but such a handkerchief- I am sure it was your wife´s- did I today. See Cassio wipe his beard with”.
At this moment, instead of wanting evidence right away, he instantly wants revenge and that feeling of revenge stays with Othello for the rest of the play. This feeling of revenge is born from a dent in Othello´s pride. The idea that Othello has only been married to Desdemona for a short period of time and he has not been able to keep her satisfied for even that long, makes Othello think that he will lose his reputation. He therefore sets out to exact revenge on the person who might have made him the gossip of Venice, and undermined his position as general of the Venetian Army. Iago does not just use the handkerchief to convince Othello of Desdemona´s unfaithfulness. Iago proves to be very good at manipulating people and how they feel. At the beginning of the play Iago successfully gets Roderigo to wake Brabantio and tell him of the relationship between Othello and Desdemona. Brabantio learns of Roderigo´s name but not of Iago´s. Iago also manages to manipulate Othello, when talking of killing Cassio. Iago adds into the conversation “But let her live”. This sounds like Iago is trying to save Desdemona, but more likely is that Iago is deliberately planting the idea of killing Desdemona into Othello´s mind. Othello replies with “Damn her, lewd minx. O damn her, damn her”. From that reaction we can tell that Iago has reminded Othello of what she has done, and rather than agree with what he has said it sounds like he is more determined to kill her. So Iago has succeeded in condemning Desdemona to death at Othello´s hands. Iago also has a nastily good way of letting Othello´s imagination do all the work convincing Othello that Desdemona has been unfaithful. He does this most effectively in his vivid description of Cassio dreaming of having sex with Desdemona. Finally Othello says to Iago “Give me a living reason she´s disloyal”, he is asking for evidence that Desdemona and Cassio have been sleeping together. Iago now conjures up a story of Cassio dreaming of Desdemona. “In sleep I heard him say. “Sweet Desdemona let us be wary, let us hide our loves”. And then sir he would gripe and wring my hand, Cry “O Sweet Creature!” and then kiss me hard, As if he plucked up kisses by roots That grew upon my lips; then laid his leg Over my thigh, and sighed, and kissed, and then Cried “O cursed fate that gave thee to the Moor”. This flamboyant description would have run havoc with Othello´s imagination, being forced by Iago to think of his wife sleeping with another man. The fact that Iago also lies that Cassio has warned Desdemona not to let Othello find out would only go further to infuriate Othello. Luckily for Iago this seems to be all the evidence that Othello needs to make the judgement that Desdemona has been unfaithful. Iago´s effectiveness at noticing innocent situations and making them look suspect is another way in which he gets Othello to believe of Desdemona´s unfaithfulness. When Othello first enters the room at the start of Act III Scene III, Cassio hurriedly leaves the room after speaking with Desdemona, Cassio does this completely innocently, he leaves because he doesn´t want to annoy Othello any more than he has already, he feels disgraced as it is and he doesn´t want to be further disgraced by having Othello send him away. Iago succesfully twist this situation- “”That he would steal away so guilty like- seeing you coming.” This is exactly what he should really be expected to do, after all the night before he had disgraced himself and when he spies the man who is most likely to be angry with him it should be expected that he would skulk off with his head between his knees. Iago twists the situation and gives the explanation for Cassio´s guilt from that he has been sleeping with Desdemona. Of course the reader knows that is not true, but to Othello, the way that he hurries away, once pointed out to him by Iago, does actually look very suspicious. This is even more enhanced in Othello´s mind when immediately afterwards Desdemona starts defending Cassio and nags on at Othello to re-instate him. This combined with Iago´s twisting of the situation looks very abnormal to Othello. Of course, the main way Iago fools Othello, is by pure luck. That luck being that a lot of the things that Cassio and Desdemona say and do fall right into the trap and further convince Othello of a relationship between the two of them. An example of this luck that Iago receives is found further on in the play when by controlling the circumstances Iago gets Cassio to talk disparagingly about Bianca, while Othello thinks the conversation to be about Desdemona. The luck of this situation is gargantuan, one mention of the name Bianca and Othello would realise who Cassio was speaking about, fortuitously for Iago, Cassio does not mention Bianca´s name once in the whole entire conversation. Iago went a long way to convincing Othello that Desdemona was being unfaithful with Cassio, yet the question must be asked of Othello why he was so willing to believe Iago with only fabricated flimsy evidence against his new wife. One would expect Othello to defend his new wife through thick and thin, especially as he has only been married to her for a very short period. Perhaps the reason why Othello was willing to believe Iago is that he trusts him completely. Othello and Iago had fought together in wars and it is most likely that, in a way, they had held each other´s lives in their hands. So Othello would never believe that Iago would turn against him so suddenly, especially as for the large majority of the play, Iago looks to be nothing more than a completely loyal servant to Othello. Also Othello, although when in Venice, appears to be a strong-minded character, proves to be quite un-confident and has a low self-esteem, this low opinion of himself may stem from being racially self-conscious. Although no mention is ever made of it, Othello views himself as different, which he is, from the rest of Venice. Therefore to Othello´s mind it must be a complete surprise for one of the most eligible women in Venice, to fall in love with him. So when Iago starts telling Othello of a relationship between Cassio and his wife, the rumours about Desdemona and what her own father had said about her may be true. Her father said when he first found out about Desdemona planning to marry Othello without his consent- “Look to her Moor, if thou hast eyes to see: She has deceived her father and may thee”. To which Othello replies “My life upon her faith”. Much of Othello deals with pride and reputation, for Othello now to hear about Desdemona´s unfaithfulness, after he replied so convincingly that he trusts her completely, would certainly start to worry him. After all, if what Iago had been telling Othello was true, then Othello had been made to look a complete fool by Desdemona in a very short period of time.