The distinction between jealousy and envy

Jealousy should not be confused with envy. In the very first scene of Othello, Iago clearly shows his envy of Cassio because he believes that Cassio has been promoted to lieutenant in his place. Iago had more experience of soldiering and was angry that the younger Cassio, whose only virtues seemed to be those of coming from a higher social class and of being better educated, should have been preferred above himself. 
‘I am worth no worse a place,’ Iago says to Roderigo, and there is some justification for his envy of Cassio. However, that does not make this attitude acceptable - Shakespeare’s audience would be familiar with the last of the Ten Commandments which prohibited the discontent which springs from the fierce desire for another’s good fortune. 
Jealousy, on the other hand, is being mistrustful of your own possessions, suspicious and anxious that you might lose something, even driven to extreme measures to keep and protect what you are afraid you might lose. That is the case with Othello, when he becomes insanely jealous on behalf of his wife, willing to do anything to stop what he believes is the treacherous behaviour of Desdemona and Cassio. 

Revenge jealousy

According to Iago, his plans to destroy the relationships between Othello, his wife and his lieutenant are a form of revenge. He reveals in his soliloquy that he himself is tormented with jealousy at the idea that both Othello and Cassio have slept with his own wife, Emilia: 
I do suspect the lusty Moor
Hath leap’d into my seat; the thought whereof
Doth like a poisonous mineral gnaw my inwards;   

And nothing can or shall content my soul

Till I am even’d with him, wife for wife;  (Act 2 Scene 1)     
For I fear Cassio with my night-cap too, (Act 2 Scene 1)     
The play presents no foundation for these convictions, but a jealous mind does not require facts to justify its tendencies. Iago knows too well the power of suggestion and a murky imagination for himself, and determines to put his master through the same torment.

Iago’s dismantling of Othello’s trust 

At the play’s opening, Othello is blissfully happy in his marriage to Desdemona. In Act 3 Scene 3 he comments on the strength of their shared love, on which he has come to rely:
perdition catch my soul 
But I do love thee, and when I love thee not, 
Chaos is come again. (Act 3 Scene 3)     
It is therefore supremely ironic that it is at exactly that moment that Iago begins his assault on Othello’s confidence in Desdemona and so sets in motion the slide into the ‘chaos’ that Othello predicted. 

Iago’s technique

Iago begins with small innocent-sounding questions: 
  • ’Did Michael Cassio … / Know of your love?’ 
  • ‘Indeed?’ 
  • ‘Honest, my lord?’ 
  • ‘Think, my lord?’ 
All of these supposedly innocuous questions serve to casually arouse suspicion in Othello that things are not all they seem. 
Iago then deepens Othello’s suspicion of Cassio’s treachery by suggesting the very opposite, ‘For Michael Cassio, / I dare presume, I think that he is honest.’ 
Next Iago cleverly warns Othello not to become jealous:
O beware, jealousy. 
It is the green-eyed monster, which doth mock 
The meat it feeds on. (Act 3 Scene 3)     
His words have exactly the opposite effect, just as Iago intended. 
Soon Iago proceeds to more definite warnings, regarding Desdemona: ‘observe her well with Cassio.’ He cleverly adds another doubt, reminding Othello that he does not know how the women of Venice behave when they are married (Act 3 Scene 3 l. 205-208). 
Within another few lines, Iago is speaking of ‘Foul disproportions, thoughts unnatural!’ Rather than be specific, he cleverly leaves Othello to dwell on his new suspicions of the bestial acts that Iago has insinuated were indulged in by Desdemona and Cassio. The fact that Iago is a trusted fellow soldier, whilst Desdemona is a frail woman whom Othello has known but a short time, only makes it all the easier for Iago to dupe him.

Fortuitous circumstances

During the lengthy Act 3, Scene 3 Iago is helped in his scheming by Emilia’s fortuitous discovery of the handkerchief which Desdemona had dropped, which she passes to her husband. By associating it with Cassio’s supposed lascivious ramblings, Iago turns Othello’s doubt into conviction about his wife’s treachery, resulting in thoughts of ‘black vengeance’ and ‘tyrannous hate.’ With his lieutenant, Othello plots Cassio’s murder and together they bow and swear vengeance in a gross parody of a prayer

Othello overwhelmed

By the end of Act 3 Scene 3 it is clear from Othello’s outburst: 
Damn her, lewd minx! O damn her! (Act 3 Scene 3)
that he has now lost all self-control. The military hero has become a slave to the demeaning tyranny of jealousy. He has changed from trusting, open-hearted love for his wife to a vengeful, violent hatred of her. This has all happened in the space of a single scene, enacted over no more than half an hour. And yet Shakespeare has made the rapid transition seem dramatically plausible by engaging the audience in the alternating tacks of Othello’s thoughts, and feeling the effectiveness of Iago’s suggestiveness. 
From this point on, Othello cannot believe that his wife is innocent, no matter how much she insists she is pure. He even refuses to believe Emilia who, as Desdemona’s maid, would be the one person to know the truth:
I durst, my lord, to wager she is honest, 
Lay down my soul at stake: (Act 4 Scene 2)     
Othello can no longer think with any logic, disregarding Emilia’s testimony compared to her husband’s. Iago has done his job well: Othello is now possessed by the tyrannical emotion of jealousy, unable to entertain any other, and so the tragedy unfolds. 

Is jealousy inevitable?

In Act 3 Scene 4 Emilia sums up the tyranny of a jealousy that cannot listen to reason:
But jealous souls will not be answered so;
They are not ever jealous for the cause
But jealous for they are jealous: ’tis a monster,
Born on itself.     
Yet Shakespeare demonstrates that this doesn’t have to be so. Although the short interlude between Cassio and Bianca demonstrates greater potential cause for valid jealousy, we feel that the two could easily be reconciled when the misunderstanding is resolved. Neither of them will allow jealousy to be their ruling emotion, even if, as Bianca suspects, Cassio doesn’t really love her. As Bianca says, ‘I must be circumstanced.’
Othello, however, chooses not to give his wife the benefit of the doubt. In Act 4 Scene 2, Emilia’s words sum up her employer’s dilemma: 
‘For if she be not honest, chaste, and true, 
There’s no man happy; the purest of her sex
Is foul as slander.’      
Henceforward, Othello is so blinded by jealousy that he can no longer recognise his wife as the loving, innocent, loyal person that she is. It motivates his hitting Desdemona in public, accusing her of infidelity with a comparative stranger, and the decision to murder both Desdemona and Cassio. 

Jealousy understood

The tragedy works to its inevitable conclusion, until Othello finally achieves a moment of clarity when he speaks of himself as:
one that loved not wisely, but too well:
.. one not easily jealous, but being wrought,
(Act 5 Scene 2)
The drama of his downfall shows only too clearly the insidious and evil power of jealousy over a naive individual who has been too blind and, ironically, too trusting, to see the truth prior to this point.
Scan and go

Scan on your mobile for direct link.