Shakespeare understood jealousy, the primary driving force behind his play Othello. It’s a common belief that the motivations of Iago, one of the all-time great villains, are never revealed and that he acts without impetus. Not true. Iago’s lust to destroy Desdemona and Othello never goes on grand display, but in Act II Iago’s soliloquy sorts out his rage, revealing what sparks his hate for Othello and in that, discovers the tool of his revenge: Jealousy.

That Cassio loves her, I do well believe it;

That she loves him, ’tis apt and of great credit:

The Moor, howbeit that I endure him not,

Is of a constant, loving, noble nature,

And I dare think he’ll prove to Desdemona

A most dear husband. Now, I do love her too;

Not out of absolute lust, though peradventure

I stand accountant for as great a sin,

But partly led to diet my revenge,

For that 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,

Or failing so, yet that I put the Moor

At least into a jealousy so strong

That judgment cannot cure. Which thing to do,

If this poor trash of Venice, whom I trash

For his quick hunting, stand the putting on,

I’ll have our Michael Cassio on the hip,

Abuse him to the Moor in the rank garb—

For I fear Cassio with my night-cap too—

Make the Moor thank me, love me and reward me.

For making him egregiously an ass

And practising upon his peace and quiet

Even to madness. ‘Tis here, but yet confused:

Knavery’s plain face is never seen tin used. 

—Othello, Act II scene i 

It appears Othello may have once slept with Iago’s wife! ‘For that I do suspect the lusty Moor Hath leap’d into my seat’. That’s Elizabethan for ‘he had sex with my wife.’ Iago cinches it with ‘Till I am even’d with him, wife for wife’. 

Iago will turn that jealousy into a tool.   In this speech the conniving bastards figures it out: ‘that I put the Moor At least into a jealousy so strong That judgment cannot cure’. 

The plan’s not completely worked out yet, but with Shakespeare’s signatory couplets–that he often used to close a scene–he promises that we’ll get to see it all: ‘but yet confused: Knavery’s plain face is never seen [till] used.’ 

To this very day, soap operas and revenge flicks still owe a kernel of their trashy existence to Shakespeare, and his uncanny insight into human nature. 

The image is of Laurence Fishburne as Othello and Kennath Branagh as Iago in the 1995 film version. Here Iago whispers poison lies into Othello’s ear.