What are the rhetorical and linguistic devices exploited by Iago to organize the plot against Othello?

First of all, considering the language used by Iago, the reader notices that his speeches are written in lines.  The choice should create in the reader’s mind the idea of an intelligent and clever character.

In addition right from Iago’s first exchange ‘Sblood, but you will not hear me!’ the reader understands the mood of the character: he is full of wrath. So the reader may suppose that Iago will use his intelligence to reach evil aims and to satisfy his anger.  

Just wrath is the first key word of the first scene. Every characters on the stage will be anger because of something: Roderigo because Iago has not informed him about an important affair, Iago because he hasn’t been chosen as Othello’s ancient and Brabanzio because of his daughter’s escape.

Going on reading the following lines, the reader recognizes other central feelings, that are: hate and jealously. It goes without saying the Othello is also called the tragedy of jealously, that is irreversibly connected both to wrath and hate: jealously is the source of the other two emotions.

It is also interesting to notice how Iago implicitly introduces the matter of love using the words ‘wife’ and ‘spinster’. Iago wants to play on Roderigo’s weakness, since he is in love with Desdemona, and proves to be able in manipulating people’s mind in secret.

To sum up, the semantic fields belonging  to the emotional sphere disclose that Iago will play on characters’ feelings and relationships, in order to take his revenge.

After Iago has explained the reasons of his wrath to Roderigo, he gradually starts to unveil his behavior: he pretends to be someone different by his true nature. Iago deepens the theme of reality and appearance, and at the same time he tells about the bound between the lord and his faithful followers.

Iago plays on people’s relationship again, deepening the theme of falsity. Iago proves to be hypocrite saying ‘I follow him to serve myself’ and double-crosser saying ‘I am not what I am’.

Now the reader has got a wider idea of the character, and it is sure that Iago will use his rhetorical skills in order to manipulate and deceive people.  

In the exchanges between Brabanzio and Roderigo, Iago sometimes intervenes. It is relevant the metaphor he uses to describe the love between Desdemona and Othello: ‘Even now, now, very now, an old black ram is tupping your white ewe’. Here Iago compares Othello the Moore to an old black ram, in order to influence Brabanzio’s mind and to damage Othello’s honor. Two lines later, Iago names the devil to refer to Othello and in another exchange he threatens Brabanzio that he will have horses as nephew, coursers for cousins and jennets for germans. Iago exploits the semantic field of animals and of devil nature to scare and influence Brabanzio. Once again he uses cunningly the rhetorical language (metaphors) to condition people.

In addition the reader may recognize the important theme of racism, by the metaphor ‘old black ram’. Iago will also plays on popular commonplaces, and once again he proves to be a skilled manipulator of reality.

In the second scene the reader gets an example of Iago’s double-cross. Indeed he pretends to be loyal and faithful to Othello and soon after, when he is alone with Roderigo, he becomes again wicked and evil.

After reading the first act the reader understands that Iago will play the most relevant role in the tragedy since he will be the puppet master of the story.