All of these themes are present in Othello, but the most dominant is the theme of jealousy, which presents itself multiple times throughout the play.
Iago, who is an ensign of Othello, is furious that he was not given the promotion of lieutenancy. Jealousy takes many forms and sometimes it is harmless while at other times it can be destructive.
Shakespeare makes Iago a puppeteer in a sense so that he may control those around him without getting caught, up until his own demise. In the volume Shakespeare and Tragedy John Bayley denies that jealousy is a major causative factor in the play: The play eludes with ease any attempt to pin it down to a solution: why it happened, what caused it, what weakness in Othello was involved?
There were four main flaws that lead to the tragedy of Othello and the others in this play; racism, love, betrayal, but it was jealousy that played a major part. This passage shows that even though Othello claims that he will not be conflicted by jealousy, step by step he is moving away from his claim and becomes jealous and filled with doubts.
One of the most amazing types of human conflict in literature is jealousy, mainly because jealousy is a well effected method of twisting human emotions, and is known to spice up almost any situation in a story.
Iago actions were consistently the actions of a man with little remorse or compassion towards the parties involved.