Loyalty and treachery are important themes in Shakespeare’s Othello from the very opening words of the play. Thus, in the very first scene, Roderigo is already accusing Iago of a mild kind of treachery (or at least disloyalty) by not informing him of Othello’s marriage to Desdemona (1.1.1-3). Iago immediately responds by claiming his loyalty to Roderigo (1.11.4-6). Iago feels that Othello has been treacherous to him by choosing Michal Cassio as his [Othello’s] lieutenant rather than Iago himself (1.1.8-17). Iago feels that he has been loyal to Othello (1.1.28-33) and thus feels all the more that he [Iago] has been treated treacherously. In turn, Iago plans to deal treacherously with Othello:
O, sir, content you;
I follow him to serve my turn upon him. (1.1.41-42)
Iago plans to pretend loyalty to Othello merely to plot revenge: “In following him, I follow but myself” (1.1.58). Within a few lines, he is already proclaiming to Brabantio that the latter has been treated treacherously by Othello, who has secretly married Brabantio’s daughter, Desdemona, without her father’s consent:
I am one, sir, that comes to tell you your daughter and the Moor are [now] making the beast with two backs. (1.1.115-17)
In other words, Iago claims that not only has Othello been treacherous to Brabantio but that Brabantio’s own daughter has been disloyal as well.
Later, in the streets of Venice, Brabantio himself accuses Othello of treachery:
O thou foul thief, where hast thou stowed my daughter?
Damn’d as thou art, thou hast enchanted her . . . . (1.2.62-63)
Later still, in the Ventian court, Brabantio once more charges Othello with treachery, claiming that Desdemona has been
abus’d, stol’n from me, and corrupted
By spells and medicines brought on by mountebanks . . . . (1.3.60-61)
When Desdemona herself appears before the court, she professes loyalty both to her father and to her new husband; she denies that she has acted treacherously but instead proclaims that now her greater loyalty must be to the man she has married rather than to the man who helped conceive her (1.3.180-89). Brabantio disdainfully accepts what has happened, but, before leaving the court, warns Othello that Desdemona may someday treat Othello as treacherously as Brabantio feels he himself has been treated:
Look to her, Moor, if thou hast eyes to see;
She has deceived her father, and may thee. (1.3.292-93)
Othello responds to this warning by replying simply, “My life upon her faith!” (1.3.294) – words that imply his own loyalty toward Desdemona as well as his trust in her loyalty toward him. Throughout the entire first act of the play, then, loyalty and treachery are crucial themes.
Other scenes in which these themes particularly appear include the following: 2.1.213-312; 2.3.204-49; 3.3.155-278; 3.3.330-480; 4.1.1-212; 42.31-90; 5.1.35-73; 5.2.1-83; 5.2.126-67; and 5.2.283-87. There are, in fact, few scenes in the play that fail to at least touch upon the themes of treachery and loyalty.