Nature of Women

There are two types of women in Othello: Desdemona represents the pure, blameless and faithful woman, and Emilia represents the woman who wishes to be given an equal footing to men, especially in regards to sexual matters.  Ironically, both ladies end up dead at the play's end.  Emilia's relaxed moral sensibility when she steals Desdemona's handkerchief is the primary cause that helps Iago to create the "Truth" of Cassio's adultery with Desdemona. However, Desdemona's respectful and submissive demeanor towards Othello also contributes to her death.  A woman more willing to seek out the cause of her husband's anger may not have been killed. 

Foolish Loyalty

From Iago's first lines in the play, Othello is established as someone who relies heavily on the advice of others.  Iago was denied a promotion because Othello took the advice of others and chose young and untested Cassio.  Iago, who Othello had seen tested in battle, was overlooked.  Iago attacks this weakness in Othello, and manipulates Othello so that he trusts Iago with a blinding faith.  Iago is even able to turn Othello's loyalty from Desdemona, whom Othello trusts in completely in the beginning of the play, when he asks her to testify that she married him of her own will. 

The Other

Othello is a dark-skinned foreigner, and although he is a strong general, he is not accepted into mainstream Venetian society.  Brabantio shows open prejudices towards him when he wishes that Roderigo would have married Desdemona rather than Othello, and Brabantio can not believe that Desdemona married Othello of her own will.  Othello also has a different set of beliefs and customs, and is not very familiar with Venice customs. This is part of why Iago can manipulate him so easily.