<span>Here're some differences and relationships between both:
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In Othello, Shakespeare begins the play with two foils, Iago and Roderigo at night: one hidden and the other in plain sight. The former is a villain, the latter a fool, but both are be dark lords of misrule.
Here's what they have in common:
<span>· </span>Both are targeting Desdemona (Roderigo as thwarted love; Iago as revenge bait against Othello)
<span>· </span>Both are jealous of Othello
<span>· </span>Both are expose Desdemona's secret elopement to Brabantio (Roderigo publicly; Iago privately)
<span>· </span>Both lose their battle against Othello in Act I (the Duke condones the marriage)
<span>· </span>Both seek revenge in Cyprus (away from the Duke's protection)
<span>· </span><span>Both are id-based characters (exhibit child-like behavior and seek immediate pleasure: Roderigo=lust; Iago=suffering of others)</span>
Here's how they are different:
<span>· </span>Roderigo is public in Venice and private in Cyprus; Iago is private in Venice and public and private in Cyprus: (as such, they are two halves of the hidden, dark side).
<span>· </span>Roderigo is pure passion (he threatens suicide); Iago is calculated passion (he wants only to wound others)
<span>· </span>Roderigo pays Iago. Roderigo is the "money" and Iago is the "purse."
<span>· </span>Roderigo is a fool. Iago admits, "I am not what I am" to Roderigo, and yet Roderigo continues to believe and pay him
<span>· </span>Roderigo thinks his using Iago for his dirty work, but Iago is really using Roderigo to be his scapegoat. Iago uses Rogerigo to expose Cassio.
Hope this helps!