Iago has a large appetite for revenge. In his perspective, he believes that it is he who should be in charge, not Othello the moor. This creates an anger in Iago, who entraps Othello in a web of deceit. He does this through a series of suggestions and hesitations that entice and implant images in Othello's head that lead to his demise. But what is more important is that he gives Othello the motive to murder innocent Desdemona. Iago is constantly like a puppet master, pulling the strings of the people around him.
There are many instances in the play where Iago is left by himself. He utilises these opportunities by telling his future plans to the audience. It would seen that he likes talking to himself about himself, which suggests he has much inner turmoil that he harbors close to his chest, but when the opportunity arises, he describes his deeds with a passion. In the first of these monologues, he makes his intentions perfectly clear. He implies that Othello has had an affair with his wife by stating "I hate the moor, And it is thought abroad that 'twixt my sheets He's done my office". The irony of this statement is that in the next line he says that he does not know it for a fact, but because he suspects it, he will act as if for certain! This gives me the impression from the beginning, that Iago is insane and exceedingly paranoid, going so far as to set up a cache of murders, just on the suspicion of adultery.
Iago was also jealous of the open and loving relationship that Othello had. When Othello and Desdemona are reunited after the journey to Cyprus, he kisses her in full view of everyone. Iago treats his wife as an object and she knows it. In Act three, Scene four, she tells Desdemona "They are but stomachs, we are but food, and when they are full, they belch us".
In Iagos' racist mind, he views his superior, Othello, as being of an inferior creed. He sees him as possessing an evil...