1. Othello was written from an imaginative standpoint far ahead of Shakespeare’s time. In a country where few people outside London would even have seen a black person, and centuries before the problems that trigger the tragedy became as widespread and acute as they are today, Shakespeare produced in Othello a critique of racial and sexual injustice that’s more powerful now in the 21^st century than it could ever have been at the dawn of the 17^th.
2. Race plays a vital but not the decisive role in bringing about the tragic catastrophe. By falling in love and eloping, Othello and Desdemona defy the paternal wrath and general hostility their interracial marriage is bound to incur. In their eyes there’s nothing illicit about their love, to which they regard themselves, and the play regards them, as fully entitled. But the racist abuse their elopement provokes from Iago and Brabantio makes the subversive implications and consequent insecurity of their mixed-race marriage clear.
3. Othello’s visibly alien identity makes him and his bride more vulnerable to Iago’s machinations than if he were an equally accomplished and indispensable upper-class white Venetian.  Their transgressive marriage forces them from the start into a defensive posture, which predisposes Othello to the suspicions that grip him so quickly at Iago’s prompting. But Othello’s vulnerability as a black outsider is inseparable from his patriarchal views of women and marriage, which prove decisive in sealing Desdemona’s fate and his own.
4. The reason why Iago succeeds so swiftly in persuading Othello to swallow his vile slander of Desdemona is that Othello is primed to believe it by the prevailing misogynistic attitudes he shares with Iago. His devious plot works by reflecting Othello’s own beliefs, confirming his suspicions and fulfilling his expectations. When Emilia begs him to deny duping Othello into murdering Desdemona, he replies: ‘I told him what I thought, and told no more / Than what he found himself was apt and true’ (5.2.176-7).
5. The disturbing thing about Iago is not that he’s unfathomably malign. It’s that his malignity is the all too predictable product of the racially and sexually divided society that created him.  The bigoted, misogynistic world of Othello confronts in ‘damned Iago’, the ‘inhuman dog’ (5.1.62), not some inexplicably evil entity but a grotesque caricature of itself. Which makes it all the more disturbing that he exploits his seductive intimacy with the audience to make us complicit with his hatred and entrapment of Othello, whether we like it or not.

Iago: Even now, now, very now, an old black ram
Is tupping your white ewe. […]
I am one, sir, that comes to tell you your daughter and the Moor are now making the beast with two backs. (1.1.87-8, 113-15)

Brabantio:For if such actions may have passage free
Bond-slaves and pagans shall our statesmen be. (1.2.98-9)

Desdemona: That I did love the Moor to live with him
My downright violence and scorn of fortunes
May trumpet to the world. […]
I saw Othello’s visage in his mind, . . . (1.3.249-53)

Iago: I hate the Moor
And it is thought abroad that ’twixt my sheets
He’s done my office. I know not if it be true,
But I for mere suspicion in that kind
Will do as if for surety. (1.3.385-9)

Othello: Haply for I am black
And have not those soft parts of conversation
That chamberers have […]
She’s gone, I am abused, and my relief
Must be to loathe her. (3.3.267-72)

Emilia: But I do think it is their husbands' faults
If wives do fall. Say that they slack their duties
And pour our treasures into foreign laps;
Or else break out in peevish jealousies,
Throwing restraint upon us; or say they strike us,
Or scant our former having in despite:
Why, we have galls; and though we have some grace,
Yet have we some revenge. Let husbands know
Their wives have sense like them: they see, and smell,
And have their palates both for sweet and sour,
As husbands have. What is it that they do
When they change us for others? Is it sport?
I think it is. And doth affection breed it?
I think it doth. Is't frailty that thus errs?
It is so too. And have not we affections,
Desires for sport, and frailty, as men have?
Then let them use us well; else let them know,
The ills we do, their ills instruct us so. (4.3.85-102)

Iago: I told him what I thought, and told no more
Than what he found himself was apt and true. (5.2.172-3)

Lodovico: Where is this rash and most unfortunate man?
Othello: That's he that was Othello: here I am. (5.2.281)

A.C. Bradley, Shakespearean Tragedy, 3^rd edn (Houndmills: Macmillan, 1992), Lecture V and Lecture VI on Othello.

Harold Bloom, Shakespeare: The Invention of the Human (London: Fourth Estate, 1999), Ch. 24: Othello, pp. 432-75.

Stephen Greenblatt, ‘The Improvisation of Power’, in Renaissance Self-Fashioning: From More to Shakespeare (Chicago: University of Chicago Press, 1980), pp. 222-54.

Karen Newman, ‘“And Wash the Ethiop White”: Femininity and the Monstrous in Othello’, in Fashioning Femininity and English Renaissance Drama (Chicago and London: Chicago University Press, 1991), pp. 71-93.

Lena Cowen Orlin (ed.), Othello: Contemporary Critical Essays (Houndmills: Palgrave Macmillan, 2004).

Kiernan Ryan's Article on Othello on the British Library's 'Discovering Literature' series