An Inability to Deal with Dissonance (2.3)
When Othello says, "Now by heaven,/ My blood begins my safer guides to rule,/ And passion, having my best judgment collied,/ Assays to lead the way (2.3.204-207)," we are surprised. Othello's fabled equanimity and calm is breaking. He begins to rage, and even though this rage apparently only lasts until he has cashiered Michael Cassio from his lieutenancy, it opens the door to the blind fury that fully develops in 3.3 and then leads to his killing of Desdemona in 5.2. But in order to understand the nature of Othello's wrath, we must understand what provoked it and how it was provoked. My conclusion is that his wrath emerged because of an inability to deal with a matter under his direct control. In addition, I think that Iago is "practicing" on Othello through his dissimulation in 3.2.179ff. in order to discover's the vulnerability that he knows must be there somewhere in Othello's personality.
In 2.3 Roderigo, as directed by Iago, provokes the drunken lieutenant Cassio into a brawl. When Roderigo runs away, with Cassio in hot pursuit, the former governor Montano intervenes and is attacked and severely wounded by Cassio (2.3.145-165). With chaos rising, Othello is roused from his marital bed and quickly takes charge of the sitaution: "Hold for your lives!" he says (2.3.165)."
Like any careful military leader, Othello wants to know the cause of the outburst. Iago feigns ignorance: "I do not know....I cannot speak/ Any beginning to this peevish odds (2.3.179-185)." Othello turns to Cassio for an explanation, but the man is too drunk to be of any assistance: "I pray you pardon me, I cannot speak (2.3.189)." Finally, he turns to the injured Montano, but he responds, "Worthy Othello, I am hurt to danger. Your officer, Iago, can inform you-- (2.3.197-198)." Feeling like a customer of a large corporation in 2004 who gets caught in an endless cycle of recorded phone messages, Othello gets angry, and bursts out in the lines quoted at the beginning. Now he is mad. He asks Iago for an explanation, and Iago, upon being prodded by Montano, blames Cassio for the problem (2.3.220-246), even though he says that Cassio only did a "little wrong." We will examine the psychology of Iago's response more closely in another mini-essay. For our purposes here, however, we have answered our question: Othello was provoked to anger because no one seemingly had an explanation for him.
Othello's Authority and Rage
But something more is happening here. Othello is not simply getting mad because he is provoked by lack of information or by an uncomfortable situation. We saw in 1.2, where Iago tried to provoke him to lose his control by pumping him in the ribs as he detailed the fearsome approach of the avenging Brabantio, that Othello remained unmoved. Fear of great and powerful senators as well as discomfort at the nagging pokes in the ribs by Iago simply did not anger Othello. He seemed to rise above these petty concerns, and his dignity and elevated manner defused a situation that could have gotten out of control.
But here he gets angry. Why? Because in this instance, in contrast to 1.2, he is in charge of the affairs on Cyprus and any disorder creates a dissonance for him that he simply cannot afford. He, after all, is in charge and must have order. When Brabantio threatened to bear down on him, in contrast, Othello simply had to stand his ground, and he did not get enraged because there was no way that he controlled or had authority over Brabantio's outbursts. The ordered body, the Senate, would have to deal with his concerns.
In New Testament terms, Othello is a man "set under authority," and he will only become enraged if dissonance in an area under his authority exists. That is precisely the situation when no one seems to be able to clarify how the civic discord happened. He must get to the bottom of any issue under his authority, and he becomes fully dependent on whoever has information who can remove his sense of internal dissonance.
Iago witnesses this behavior of Othello. He has seen that Brabantio's threats and his own pokes to Othello do not rile the great man. Now he sees that something does get him enraged. It will be the withholding of information in an area under Othello's authority. And, Iago is brilliant. He will store this incredibly important datum in his memory bank, and bring it out to torment Othello into near lunacy in 3.3. Now Iago will not only have Cassio in his debt, but he has just learned how to catch Othello in his net. A little riot well worth it!