Cassio and the loyalty of Desdemona. Iago would probably have thought of a way to sow such seeds in any case, but the chance departure of Cassio from Desdemona, just as Othello approaches, provides an ideal opportunity for Iago to begin to work his evil magic.

• The most famous example of chance or coincidence in the play is the accident of Desdemona dropping the handkerchief when Emilia is nearby to retrieve it and later give it to Iago. She loses the handkerchief because Othello, by chance, just happens to have an epileptic episode that causes Desdemona to wipe his forehead with the cloth that means so much to him. Losing the handkerchief is one thing; losing it when Emilia is nearby to see it lost is another. The results of the loss of the handkerchief, of course, prove disastrous.
• Another example of bad luck occurs when Desdemona, trying to distract Othello from the topic of the lost handkerchief, chooses precisely that moment to urge him to show mercy to Cassio. Ironically, every time she pleads on Cassio’s behalf, she only (inadvertently) makes Othello more and more jealous and enraged.  She could have tried to distract him by talking about almost any other subject, but instead, by chance, she talks to him about the one subject that will anger him the most.
• Later, by chance, Othello happens to have an epileptic episode just as Cassio happens to approach. The episode gives Iago the opportunity to deceive both Cassio and Othello (when Othello comes back to consciousness).
• Then, by chance, Bianca happens to approach just when Othello can see (but not really hear) her interacting with Cassio, and, by chance, she has brought the handkerchief with her, which she has found by chance.

Chance, then, plays a crucial role at various points throughout Othello. In fact, one seventeenth-century critic of the play joked that the moral of the work is that ladies should be careful not to lose their linen. The play does emphasize the roles of personality (especially the personalities of Othello and Iago) and design (especially Iago), but chance and coincidence are also important factors in this drama.

In Aristotle's Poetics, hamartia is identified as the fatal flaw that brings about the downfall of a tragic hero, turning a protagonist blessed with good fortune into a victim of tragic destiny. Shakespeare's The Tragedy of Othello meets the definition of a tragedy because within Othello's character is a fatal flaw that leads to a chain of events that culminates in his demise. In this way, Othello's character becomes his destiny.

Othello's fatal flaw is his self-doubt, which leads him eventually to embrace a perception of himself that is undeserving of the love of Desdemona. Though Othello is a decorated war hero, and an upstanding leader and citizen, he is black and he is older than Desdemona; both of these qualities render him insecure in his position as Desdemona's husband. Iago capitalizes on Othello's self-doubt, planting seeds of suspicion regarding Desdemona's fidelity, and these seeds take root quickly and violently because Othello himself understands why Desdemona would supposedly cheat on him with a white man. Iago's plan to undermine Othello is tragically successful, as the events that lead to Othello's suicide all could have been avoided if only Othello had the confidence to realize that he does indeed deserve Desdemona's love and loyalty.

In Othello character does become destiny in many ways. Iago uses the other characters's weaknesses to his advantage, and of course his own sinister nature plays a role as well. Othello is a man of great loyalty and courage, but he is also quick to anger, prideful, and jealous. He is inclined therefore to believe Iago on scant (albeit convincing) evidence that Desdemona has been unfaithful to him. His pride and natural tendency to anger lead him to react rashly in this moment rather than logically. Because of these character imperfections, an otherwise good man becomes a murderer. In this sense Othello's character becomes his fate.

This is also only possible because of the flaws of other characters. Emilia is too compliant with her husband's wishes when she places the handkerchief, and Cassio falls victim to his tendency to over-drink. Above all, Iago's massive moral bankruptcy and envy towards Othello and Cassio are what set the tragedy in motion. The outcome of the play is entirely the result of the tragic shortcomings of its principal characters.

In act 5, scene 2, Othello cries, "Who can control his fate?" as he looks around at the ruins of his life, particularly his beloved Desdemona, who is now dead because of his own cruelty. Through the conflict they face, their love seems fated to end tragically.

Iago treats Othello unfairly at least in part because of Othello's race. When he is trying to rouse Brabantio's feelings of anger against Othello, Iago resorts to racist insults:

Even now, now, very now, an old black ram
Is tupping your white ewe. Arise, arise!
Awake the snorting citizens with the bell,
Or else the devil will make a grandsire of you. (I.i.97–100)

Being born as a Black man was part of Othello's fate, yet it causes men like Iago and Brabantio to see him as unworthy of the fair Desdemona's love.

There are other examples of fate that further the conflict in the story. One crucial example is the moment when Desdemona accidentally loses the handkerchief that Othello had given to her. This becomes a central point of conflict in the play, as Othello comes to believe that this is evidence of his wife's infidelity.

By nature, Othello is also a jealous man, which is linked to his demise. He is fated to see evidence that convinces him that his wife is unfaithful despite her protests. When he watches Cassio laughing with Iago, Othello mistakenly believes that this is evidence of Cassio's affair with Desdemona.

In his remorse, Othello reflects that Desdemona was an "ill-starred wench" (V.ii.286), her tragic fate written in the stars; thus, Othello was also fated to meet a tragic end the moment he fell in love with her.