As soon as they enter, he hints at something unusual going on, saying “Ha, I like not that” (3.3.34), disguising his deliberate act by making it look like a harmless utterance to himself. Of course, he knows that it is in Othello’s nature to pick up on this and purposely tries to cover his tracks while in fact continuing to make suggestions and “spread the poison”. When Desdemona greets him, her choice of words to describe Cassio are unfortunate as “suitor” has romantic connotations which, although she does not mean, Othello could certainly take the wrong way, especially after Iago’s pretence.
After Desdemona departs, Iago continues to insinuate that there is something going on between the two, but he refrains from saying too much or going into any detail – indeed, it should be noted that the most direct accusation he makes throughout the entire scene is “I cannot think it that he would steal away so guilty-like” (3.3.48). He then begins to echo Othello’s words, setting him even more ill at ease. He questions, although seemingly harmless, are actually fundamentally relevant to the issues at hand. As Iago draws Othello in more and more, he makes him believe that his statements are to hide a truth that he does not want his general to see whereas in reality they are all feigned to make Othello jealous and get him to start questioning Desdemona himself. Othello himself says “Thou echo’st me as if there were some monster in thy thought too hideous to be shown” (3.3.109), showing how Othello is starting to be led by the insinuations in Iago’s words – even though up to this point Iago has cleverly made no indication that there is no “monster” – he has asked harmless questions.
He then moves on to what he thinks of Cassio. He regards him as honest – “I dare to be sworn, I think, that he is honest” (3.3.127) – but Iago’s deliberate feigned tone of uncertainty sets Othello off again in thinking that he knows more than telling. Seeing the effect this has on Othello, he continues, saying “Who has a breast so pure but some uncleanly apprehensions keep leets and law days”. He implies that Cassio is in some way flawed but again makes no explicit remark that names Cassio as the subject of the statement. He has created an opening for himself here and goes on to allude that he knows something about Cassio. “Good name in man and woman…is the immediate jewel of their soul…but he that filches from my good name, robs me of that which enriches him and makes me poor indeed” (3.3.157) is a statement which Iago deliberately intends for Othello to misinterpret and make it look as if he is hiding something to protect Cassio’s good name.
Iago then tells him to “beware of jealousy” which is ironic because up until this point Othello has displayed no outward sign of being jealous – he is more concerned with getting the truth out of Iago than what the truth could be – but Iago is now directly implying that he has something to be jealous about. Othello picks up on this, and defends his wife, believing her to be virtuous and merely enjoying Cassio’s company, but Iago, showing his talent for improvisation, points out that Desdomona lied to her father about her marriage and hid her love for Othello when they met - “She did deceive her father, marrying you, and when she seemed to shake and fear your looks, she loved them most.” (3.3.209).
The most important aspect of this scene then becomes the proof which Othello demands of Iago of the alleged affair - he demands that he provides “ocular” proof as evidence of her guilt. Iago, once again clever improvising, subverts Othello’s wish for “ocular proof” by making him see that this would mean catching them in the act, which would, he implies, be painful for Othello to witness – “Would you, the supervisor, grossly gape on? Behold her topped?” (3.3.398). As a now distraught Othello realizes this, Iago digs deeper, relating the tale of how Cassio talks in his sleep. The detail in which he describes Cassio’s actions makes them all to vivid for Othello to dismiss – indeed he works himself up into such a state that he now take Iago’s tale as a piece of true evidence against Desdemona!
By the end of the scene, it is clear that Iago has achieved his aims – blinded by anger and rage, Othello abandons his need to find proof of his wife’s actions, instead just taking Iago’s mere speculations and observations as all the proof he needs.