The most prominent form of prejudice on display in Othello is racial prejudice. In the very first scene, Roderigo and Iago disparage Othello in explicitly racial terms, calling him, among other things, "Barbary horse" and "thick lips." In nearly every case, the prejudiced characters use terms that describe Othello as an animal or beast. In other words, they use racist language to try to define Othello not only as an outsider to white Venetian society, but as being less human and therefore less deserving of respect. Othello himself seems to have internalized this prejudice. On a number of occasions he describes himself in similarly unflattering racial terms. And when he believes that he has lost his honor and manhood through Desdemona's supposed unfaithfulness, he quickly becomes the kind of un-rational animal or monster that the white Venetians accuse him of being.
Yet racial prejudice is not the only prejudice on display in Othello. Many characters in the play also exhibit misogyny, or hatred of women, primarily focused on women's honesty or dishonesty about their sexuality. Several times, Othello's age is also a reason for insulting him. In all of these cases, the characters displaying prejudice seek to control and define another person or group who frighten them. In other words, prejudice works as a kind of strategy to identify outsiders and insiders and to place yourself within the dominant group. And Othello himself seems to understand this—he concludes his suicide speech by boasting that he, a Christian, once killed a Muslim Turk, a "circumcised dog" (5.2.355) who had murdered a Venetian citizen. Othello tries to use religious prejudice against Muslims to cement his place within mainstream Christian Venetian society.
The tragic plot of Othello hinges on the ability of the villain, Iago, to mislead other characters, particularly Roderigo and Othello, by encouraging them to misinterpret what they see. Othello is susceptible to Iago's ploys because he himself is so honest and straightforward. As Iago puts it: "the Moor is of a free and open nature/ That thinks men honest that but seem to be so; and will as tenderly be led by th' nose/ As asses are" (2.1.391-4)
In Othello, Shakespeare plays with the idea of unreliable reality in a number of ways. The language of the play, which time and again refers to dreams, trances, and vision, constantly highlights the way in which what seems to be real may actually be fake. In addition, Shakespeare extends the theme of appearance vs. reality to include the art of playwriting and acting. As he develops his plot against Othello, Iago creates scenes within scenes. He sets up encounters between two characters and putting a third in the position of a spectator. For instance, he has Othello watch Cassio and Desdemona speak, and he has Othello watch him speak with Cassio about Bianca. In each case, Iago manipulates Othello so that Othello sees the appearance that Iago wants him to see, rather than the reality of what is actually happening. In this way, Iago becomes a kind of "director"—he even directly addresses the audience through his many soliloquies—and Shakespeare draws attention to the way that a playwright and actors create an appearance onstage that tricks the audience into seeing something other than reality.
Iago refers to jealousy as the "green-eyed monster." As this metaphor suggests, jealousy is closely associated with the theme of appearance and reality. For instance, at one point Othello demands that Iago provide "ocular proof" of Desdemona's infidelity—he demands to see reality. But Iago instead provides the circumstantial evidence of the handkerchief, which Othello, consumed by his jealousy, accepts as a substitute for "ocular proof." Othello's jealousy impedes his ability to distinguish between reality and appearance. While the prejudiced characters in the play denigrate Othello as an animal or a beast based on his race, Othello's obvious honor and intelligence makes these attacks obviously ridiculous. Yet when Othello is overcome by jealousy, he does become beast-like, falling into epileptic fits that rob him of the ability to speak intelligibly.
Othello is also not the only character in Othello to feel jealousy. Both Iago and Roderigo act to destroy Othello out of jealousy, with disastrous consequences.
Throughout the play, various male figures seek to assert and protect their manhood and their honor. Based on the Duke's regard for him in 1.3, it is clear that Othello has attained political power through his military might. The subplot in which Iago gets Cassio drunk and causes him to humiliate himself, also indicates the importance of "reputation, reputation, reputation." In fact, Cassio asserts that reputation is all that makes you human ("I have lost the immortal part of myself, and what remains is bestial" [2.3.252-3]). Iago asserts—however genuinely or disingenuously—that reputation is more valuable than anything in the world: "good name in man and woman [...] is the immediate jewel of their souls" (3.3.156).
Though military exploits are one way for men to build their honor, when not in war the primary means by which men define their honor is their ability to command the faithfulness of their women. In 1.1, Iago and Roderigo call Brabantio's honor into question because he hasn't been able to control the romantic or sexual impulses of his daughter, Desdemona. Later, Iago drives Othello to question his own manhood—indeed, his very humanity—by making him doubt whether he has power over his wife. In despair over his suspicions about his wife's faithfulness, Othello laments of himself: "A horned man's a monster and a beast" (4.2.62). That is, in his view, to lose control of the woman in his life is to lose everything that makes him human. In other words, without his honor, he sees himself in the same terms that the prejudiced characters see him: as an animal.
Two contrasting images of womanhood dominate Othello: the virtuous and loyal woman, or Madonna, embodied by Desdemona; and the whore, embodied, to a certain extent by Bianca. Yet over the course of the play, it becomes clear that these two different ways of describing women don't actually apply to real women. Instead, they are male fantasies imposed on women—ideals that men want woman to fulfill, and roles that women therefore purposefully play for men. For instance, Desdemona often describes her devotion to Othello in front of other people, underscoring that, even though she does love him very deeply, she is to a certain extent playing the role of the virtuous wife. Iago then stokes Othello's jealousy in part by forcing Othello to realize that there is no way for a man to tell the difference between a truly virtuous wife and one who is just playing the role of virtuous wife while actually acting as a whore and being unfaithful.
Meanwhile, Iago's wife, Emilia, complicates the simple contract between the Madonna and the whore. Initially, she wants to please her husband—and does so by stealing Desdemona's handkerchief, knowing that he has long hankered after it. Yet she is not wholly loyal, and even tells Desdemona in 4.3 that she believes many women, including she herself, would cheat on their husbands under certain circumstances. And, finally, she proves her own, independent virtue by defending Desdemona's virtue and revealing her husband's crimes in the process. So while womanhood in Othello is, therefore, often defined by men in terms of pure virtue or voracious and deceptive sexuality, the play ultimately shows that real women are far more complex.