What motives are suggested for Iago's behavior and why are we to question the statements that reveal those possible motives?
There are a number of reasons given for Iago's motives in the play and a number that the audience may infer from the play. Iago tells us that he feels aggrieved that Othello chose Cassio to be his Lieutenant instead of him, despite the fact that Iago had served Othello faithfully for many years. There is the petty rivalry between Iago and Cassio as a "Florentine" from Florence rather than a true Venetian; and between the experienced Iago and the "bookish" Cassio "that never set a squadron in the field". It is a conflict between the new and old world, experience and theory, the feudal and modern worlds.
In addition to this, Iago's language is overtly racist about Othello and crude about his relations with Desdemona ("an old black ram is topping your white ewe") that we may infer that his animosity is motivated by either racism or sexual jealousy.
Finally, his hatred may also be unmotivated and undirected, merely just a part of his character that lights on any pretext to cause trouble and difficulty for others.
In the play Iago gives petty motives for the pain and tragedy that he causes. He accuses Othello and Cassio of cuckolding him but has no evidence to prove his accusations. He also believes that he deserved the position of lieutenant that Othello gave to Cassio. He says that Othello has “done my office.” Later in the play Iago makes it clear that he himself does not believe his own accusations. This proves that Iago does not act out of revenge. Samuel Taylor Coleridge describes Iago’s motives as "the motive-hunting of a motiveless malignity." It is clear that Iago has no real motivations to create such chaos in the lives of the other characters in the play. He commits evil acts simply because he has the power and influence to do so. He wreaks havoc on the lives of the characters in Othello for his own “sport and profit"
one could argue however that it is Iago's envy that drives him rather than the petty motives he describes in his soliloquys. It is clear that envy has a huge amount of influence on Iago’s mind. Iago is envious of Cassio because Cassio has lived a privileged life. Cassio is good looking and won the position of lieutenant. Iago says: "Cassio hath a daily beauty in his life, that makes me ugly." Iago is envious of Othello’s power and authority in the army; he is also racist as seen in the first scene of the play where Iago constantly refers to Othello as a beast. Iago may feel that it is not right that he should have to look up to Othello, who is a moor in Venetian society. Iago is also Envious of Roderigo’s money. Perhaps Iago’s mind is so consumed with envy of others that this is motivation enough for him to act so inhumanly.