Othello is a play about jealousys causes and effects. Each character in the play had different reasons to be jealous and each of them chose to deal with it a certain way. All three characters Iago, Othello, and Roderigo had such cases and in the end dealt with different conflicts and outcomes. Its important to understand that their actions in dealing with their jealousies were a reflection of their characters, and persona. In the first scene, Iago was seen in the middle of a conversation with Roderigo. This opening scene sets forth the key elements to understanding Iagos basic character and the plays conflict.
The scene revealed Iagos deep resentment toward Othello and his outlook on himself as a soldier. And I of whom his eyes had seen the proof / At Rhodes, at Cyprus, and on [other] grounds / Christened and heathen must be beleed and calved (1.1.29).
Iago stated this to Roderigo trying to prove his worthiness and experience in comparison to Cassio, who was appointed the position Iago wanted. This statement undermines his self-esteem. Because of his self-indulgence, we are inclined to believe his superiority as a warrior. Iago points out to Roderigo that Cassio, the newly appointed lieutenant, is not a true soldier.
Iago says Cassio knows more division of a battle (1.1.23) than this bookish theoric (1.1.24).
Furthermore, there is nothing Iago can do about the situation: theres no remedy (1.1.35).
He realizes that preferment goes by letter and affection (1.1.36) and not by old graduation (1.1.37).
So Iago will continue serve Othello, so that eventually he can serve [his] turn upon him (Othello) (1.1.42).
As the reader, we get a clear-cut picture of where Iago was coming from, and we were forced to sympathize Iagos position. In order to disguise his deep dissapointment and conceal his plans for revenge (which was his choice of action), Iago begins early in the play to reinforce his image as being an honest and loyal soldier.
In Act I, Scene 2 for example, in a bit of playful boasting, Iago says that in the trade of war I have slain men, / Yet do I hold it very stuff o the conscience / to do contrivd murder I lack inequity (1.2.1-3).
This was an outright lie, but he had come on stage with Othello and he said this for his generals (Othellos) benefit, posing as the rough and ready , but good hearted soldier. Iago also hides his contempt for Cassio because Cassio is a fellow soldier. Because Iago pretended to be something he wasnt, throughout the play he was forced to lie repeatedly to everyone in his path. It is possible that Iagos wit cyncial though it is saves him from being a hateful scoundrel for the entire duration of the play..