Iago's soliloquy explores Iago in great detail and gives an insight into the events that are to follow. Iago's character, frame of mind and the situation at this point in the play is conveyed through various methods. In this soliloquy Iago's wicked nature and sadistic obsession to create a catastrophe is shown. He also demonstrates how manipulative and deceitful he is. The soliloquy highlights how Iago displays signs of madness.
The soliloquy shows the raging evil within Iago. Up to this point in the play, Iago has had a racist attitude, always insulting Othello. His racism is seen through him calling Othello "the Moor" in the soliloquy instead of his actual name. Iago uses the term "blackest sin" metaphorically to mean the worst sin possible, confirming his racist prejudice towards dark-skinned people, especially Othello. Not only is Iago racist to Othello, but also wishes to cause suffering to others without any real motives.
He has decided to set Cassio and Desdemona up so that Othello will become suspicious on whether Desdemona is a loyal wife or having an affair. Iago mentions that he will "pour this pestilence into his ear' which will "undo her credit with the Moor." Earlier on in the same scene, Othello had dismissed Cassio because Othello had thought that Cassio has a drinking problem, due to Iago's manipulation and evil. However, the fact Iago is continuing further to harm Cassio's reputation exemplifies the villainous mind of Iago.
Iago's deception and manipulation is illustrated in the soliloquy. In order to cause Othello to suspect Desdemona of having an affair with Cassio, Iago sets up a plan so that Othello thinks Iago is helping him but is actually being misled as well as doing the same thing to Cassio. Iago tells about the further misguidance he will do stating in the soliloquy "I'll pour this pestilence into his ear," indicating that he is going to suggest to Othello that Cassio secretly loves Desdemona. Iago refers to Cassio as an "honest fool," which suggests that Iago will attempt to fool Cassio in some way. Iago deceives Othello and Cassio through their weakness of being too good-hearted and trusting, which in fact becomes gullibility. Iago observes their trusting personality by uttering "To counsel Cassio to this parallel course Directly to his good?" Iago is also confident that his manipulation will work by mentioning Desdemona "shall undo her credit with the Moor." The manipulation that Iago has used thus far and how he will use more in the soon future is seen very clearly by this soliloquy.
The strange mentality of Iago is demonstrated through what he says in the soliloquy. Though there are times where Iago is proud of being a villain who is tormenting Othello's life, in this soliloquy he tries to convince himself that he is in fact not a villain. He says such remarks as "he then that says I play the villain When this advice is free I give, and honest" as well as "How am I then a villain." Iago persuades himself that he has many motives to avenge Othello yet none of them are justifiable reasons. He ends up falsely believing in his own suspicions and thoughts. He believes that "her (Desdemona) appetite shall play the god With his (Cassio) weak function." and "His soul is so enfettered to her love." Earlier on Iago says I Act II, Scene I "Cassio loves her," "I do suspect the lusty Moor," and "I fear Cassio with my night-cap too." These are all simple thoughts that have popped up into Iago's head, which eventually are used as justifications to himself for his vile actions. In addition however, Iago contradicts these statements later on in the soliloquy. He concludes in his soliloquy "And out her own goodness make the net That shall enmesh them all." This implies that in reality Iago has no real motivation but instead is doing it in order to have some fun.
So much is conveyed about Iago's character, frame of mind and situation at this point in the play through the language in this soliloquy. The soliloquy provides an insight into Iago displaying his evil fantasies. The methods in which he manipulates the others characters in the play is shown through the soliloquy. His soliloquy tells that Iago's mind is in total disorder, which in effect is the catalyst to the events to follow.