Act One Scene 1 Questions

What is wrong with Micheal Cassio? 
According to Iago Cassio is under experienced compared to himself. He says that he knows as much about was as an unmarried woman also called a "spinster" knows about war. Iago also mentions Cassio's lack of  experience saying he"never set a squadron in a field," (1.1.23)

How does Brabantio think Othello has won Desdemona? 
Brabantio thinks Othello has won Desdemona over with which craft. This is shown by his reaction to Rodrigo when he tell him that his daughter and Othello are married. He asks Rodrigo "is their not charms"(1.1.171)  meaning have you heard of any witchcraft that could make her do that.

Is there anything in his words and actions to make us doubt Iago's honesty?
While the other characters should not trust Iago, he has proven to be honest when addressing the audience. While he is starting to manipulate the situation by pretending to be honest with the other characters such as Rodrigo he lets the audience honestly know that he is being manipulative by stating "I am not what I am."(1.1.66) This mean Iago is putting on an image of himself to the other charters which is not his genuine self.

What are our thoughts on Othello after Act 1 Scene 1
Our thoughts on Othello are only based on how he is described in this point of the play having not yet meet him. He is described as "lascivious,"(1.1.126) which means revealing an overt and often offensive sexual desire, so his is described to us as a very lustful man. Othello is also described as a "horse," whose relatives will neigh at Brabantio. This gives the reader an Image of a animal with animal like qualities. 

Why do we believe Iago?
We believe Iago because he is honest with the audience from the start. When he says " I am not what I am,"(1.1.66) he lets the audience on his true character right away. This gives the audience a sense of insurance that he will tell them the truth because he lets them know his true nature so we don't have to guess if he is being honest or not.  

Why does Brabantio react the way he does?
Back in the time of the Renaissance fathers spend a lot of time preparing their daughters and finding them good husband. Brabantio states he has spent alot of time on his daughter when he says " what's to come of my despised time,"(1.1.161) meaning by her getting married all the time her father spent in preparing her for  a noble good standing man was wasted when she married a man she picked.