To what extent is Iago responsible for the tragic happenings in Shakespeare's Othello?

Iago is the smartest villain among all the villains. Though Iago is mostly responsible for the tragic happenings in the lives of most of the leading characters in Othello, he proves himself as an ambidextrous manipulator.  As a villain Iago has almost supernatural ability to manipulate the other characters of the play. He manipulates the other characters into following their own agendas and all the while coming closer to his goal of bringing Othello to his downfall. 

The villainy of Iago is great in the sense that he had an elaborate plan, using every character in the story and manipulating their minds to the point where everyone was believing lies. He did all of this so that he could get what he wanted-the destruction of Othello. Through Iago’s subtle manipulation each event moves along the plot and has a direct effect on the emotional responses of the characters. The decisions that are made prepare the dramatic conditions for the next tragic event.   Right from the beginning of the play, Iago’s involvement in the play is evident.

The play begins with a conversation between Iago and Roderigo. From their conversation it appears that Iago has been overlooked by Othello for a promotion. This makes him vengeful and his first action is to tell Brabantio that Othello has eloped with his daughter, Desdemona.   Iago’s behaviour and method of disclosure is designed to deliberately alarm Brabantio and give him a dreadful shock. Iago wants to poison Brabantio’s mind against Othello. Here Iago appears as a racist. Iago uses racism as a spark to inflame Desdemona’s father, Senator Brabantio, against Othello..After Iago and Roderigo raise a clamor outside Brabantio’s house late one evening, the senator awakens and comes to a window. Iago then uses vulgar animal imagery to slur Othello, telling Brabantio that the black Moor has seized his greatest treasure, his daughter, and at that very moment is defiling her. 

Iago shouts to  Brabantio

... now, very now, an old black ram 
Is tupping⁵ your white ewe⁶. Arise, arise! 

There is an obvious racism in this quote. When Brabantio reacts with incredulity, Iago replies with a metaphor that this time compares Othello to a horse: ‘you’ll have your daughter covered with a Barbary horse.’

But here Iago fails to achieve his end namely the fall of Othello. The court declares Othello innocent and consents to the marriage between Othello and Desdemona. But Iago is not the man to give up. Iago follows Othello like a shadow. And it is Iago who plants the seeds of suspicion and jealousy in Othello’s mind and brings down the ultimate tragedy in the play. 

Iago goes to Cyprus and his next concern at Cyprus is to bring Cassio into disrepute which he proposes to effect by making Cassio drunk. Iago gives to Montano the impression that Cassio is a habitual drunkard and therefore unfit to be Othello’s lieutenant. Asked if Cassio often gets drunk, Iago replies that Cassio cannot sleep without heavy drinking. He here tells a brazen lie but in such a possible manner that Montano, he prepares that man to fight with Cassio, just as he has already  prepared Roderigo, also by telling him lies, to provoke Cassio into a quarrel. After having suggested to Cassio to seek Desdemona’s help, Iago sets forth his strategy in a soliloquy. He will draw the Moor apart for a while and then bring him precisely when he can see Cassio “soliciting” Desdemona at a distance.

Iago has an amazing genius for plotting and for manipulation. Apart from the credulity of his victims, he succeeds because of his fertility of mind in inventing lies and falsehoods and in lending plausibility to whatever he says or invents. He drives Othello desperate and almost mad with jealousy. Iago’s whole manner of talking to Othello in the great “temptation scene” is so plausible, so persuasive, and so skillful that Othello easily falls into the trap. The Act 3,Scene 3; often called the "temptation scene," is the most important scene in the entire play and one of the most well-known scenes in all drama. In it, Iago speaks carefully and at length with Othello and plants the seeds of suspicion and jealousy which eventually bring about the tragic events of the play.

Iago arranges to be walking with Othello when they just "happen" to see Desdemona and Cassio talking quietly. Iago causes Othello to see the infidelity of his young and beautiful wife, Desdemona, with his favorite lieutenant, Michael Cassio. Indeed, Othello does not see the gap between appearance and reality. His "Ha! I like not that!" (35) is a blatant lie; this fraudulent tsk-tsking hides Iago's true delight; nothing could satisfy his perversity more. But because Othello sees nothing amiss, Iago must make a show of not wanting to speak of it, or of Cassio, while all the time insinuating that Cassio was not just leaving, but that he was "steal[ing] away so guilty-like" (39). Iago's words here are filled with forceful innuendo, and as he pretends to be a man who cannot believe what he sees, he reintroduces jealousy into Othello's subconscious.

Iago makes suggestive comments to Othello about Cassio's way with the women and his relationship with Desdemona. When Iago is alone with Othello, he resumes his attack on his general's soul. Out of seemingly idle curiosity, he asks if Desdemona was correct when she referred to the days when Othello was courting her; did Cassio indeed "know of your love?" (95). Here he prods Othello's memory to recall that Desdemona and Cassio have known each other for some time. Then again playing the reluctant confidant, he begs, as it were, not to be pressed about certain of his dark thoughts. One can see how skillfully Iago makes use of his public reputation for honesty.

Iago is a misogynist, who warns Othello to watch his wife closely (so that he will notice all the ways in which Iago plans to frame Desdemona and Cassio). He reminds Othello that Desdemona is a Venetian lady and "in Venice they [wives] do not let [even God] see the pranks / They dare not show their husbands" (202–203). In other words, the faithless wife is a well-known member of Venetian society. Iago also attempts to frame Emilia as a duplicitous woman, indeed all women, as one who would "rise to play and go to bed to work"(113).

In achieving his goal namely the fall of Othello, Iago employs various devices. He later drops Desdemona’s handkerchief in Cassio’s apartment and then tells Othello that he saw Cassio wiping his beard with it. He invents a dream in which Cassio is supposed to have made love to Desdemona and to have cursed the Moor. He questions Cassio about Bianca and makes Othello believe that he is talking to Cassio about Desdemona. And he arranges matter in such a way that Cassio should not meet Othello face to face because a meeting between them is likely to lead to an exposure of Iago’s falsehoods. His designs against Cassio and Roderigo are also well-executed. His last move against Cassio and Roderigo is one of the masterpieces of his devilry, though unhappily for him, it miscarries. Here he literally wanted to kill two birds with one stone.  Besides he remains perfectly cool and composed throughout. Except once and then also for a few moments, he does not lose his nerve at any stage throughout the play. In having brought about the destruction of Othello and Desdemona he does not feel the least regret or remorse. He is a totally unrepentant evil-doer. His cruelty is remarkable. He feels not the least pity for the innocent and trustful Desdemona; nor does he shrink from stabbing to death his own wife or Roderigo.

No doubt Iago is the most contemptuous character in the play Othello. But as a character he has some remarkable qualities. Iago possesses a vast knowledge of human nature and human dealings; otherwise he could not have been such an effective schemer and manipulator. He gives us, in the course of play, several generalizations which, if read apart from the context, would seem to be unquestionable truths. His remarks about how promotions are granted on the basis of the personal preferences of the employer, his comments on virtue and on reputation, his references to false appearances which people put on and to the foul thoughts which enter even the noblest minds-all these carry conviction.

If one looks in modern day cinema, one will see the trite villain, evil to the core. Shakespeare took his villains to a higher level. He did not make them transparent like the villains of modern cinema. He gave his villains depth and spirit. Iago is a perfect example of "Shakespeare's villain." His amorality and cynicism give, what would be a very dull character, life. the villainy of Iago did cause a lot of despair and cost many characters their lives in Othello.