Kernan believes that Roderigo is part of the structure of the play as it develops the idea of the breakdown and final reestablishment of society. Kernan sees this progression as reflected in the shift from Venus to Cyprus in the course of the play. There are forces in the city threatening traditional social forms and relationships, and these forces center on Iago:
His discontent with his own rank and his determination to displace Cassio endanger the orderly military hierarchy in which the junior serves his senior. He endangers marriage, the traditional form for ordering male and female relationships, by his own unfounded suspicions of his wife and by his efforts to destroy Othello's marriage by fanning to life the darker, anarchic passions of Brabantio and Roderigo (Kernan 83).
Iago first stirs the followers of Brabantio to seek revenge, and then he deliberately starts a fight with Roderigo to foster a brawl in the streets. Roderigo serves as an alter-ego to whom iago speaks and to whom Iago expresses his antisocial impulses, as in the advice Iago gives Roderigo when he tells him how to call out to Desdemona's father about the marriage, saying to do so "As when, by night and negligence, the fire/ Is spied in populous cities" (I.1.73-74).
Cassio and others fail to see the depth of Iago's evil nature, and they also see him as honest. If they did not trust him, it would not be possible for him to manipulate them as he does. Roderigo is more aware of the fact that Iago is not completely honest, but he accepts that Iago is at least honest with him, which is not the case. Cassio and Roderigo have characteristics which make them susceptible to Iago's manipulations. Cassio for his part is loyal and yet is treated unfairly by Othello. He is dismissed from his post as an example to the other lieutenants, and Othello refuses to reinstate him because of a certain stubbornness on his part and a refusal to reverse himself. Cassi...