An argument can be made that societal prejudice leads to Othello's actions. He begins the play in a position of power in two ways—through the military and through his marriage. Because Othello is black, this would have been a problem in Venetian society, both when Othello was written, in the early 1600s, and slightly before, when its parent text was first published. Because of his race, the power that Othello gains is viewed as ill-gotten, especially by Iago (who is ultimately his undoing).
If it was only society that questioned the validity of Othello's position, he may have been able to persevere despite the prejudice. I would argue, though, that Othello's true fatal flaw is his self-doubt. He is entrenched in racist attitudes so far that he believes the worst in himself. As such, he values his reputation more than his own convictions. When he first considers the possibility of Desdemona's infidelity, he becomes angry.
Her name that was fresh
As Dian's visage, is now begrimed and black
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