I think that one of the best elements that is evident in "Othello" is the idea that human machination and calculation can results in one of the worst crimes that individuals can perpetrate upon one another. Iago's plotting against everyone, the manner in which he uses people, and the way in which he fully understands how human weakness can be manipulated into another's benefit are all examples of a statement Shakespeare might be trying to make regarding our interactions with one another. At a time in intellectual history when humans were seen as instruments of the divine or in a singular manner, Shakespeare was radical for suggesting that there are a multiplicity of motivations and rationalizations behind why people act the way they do. Additionally, I think that Shakespeare might be suggesting that envy and coveting what others have can prove to result in a hollowness of resentment which there can be little alleviation. While Iago is really bad- I mean, really bad- there is a certain sadness in recognizing that he is beyond redemption because of the resentment and anger he harbors within his own heart.
One cannot know with certainty what Shakespeare had for the purpose when he wrote the play "Othello," but a guess can certainly be extrapolated. Since it is a tragedy, and he had written others, the simple definition or formula of the tragedy is probably not the most important element in the play. One of the interesting things about the play is that Othello's confidant is actually his undo-er. And, the fact that Othello had completely put Iago in his confidence, it says a great deal about how one should really know their trusted friends. This i snot one of the elements that is common to many plays. There may be friends who are jealous of another, but in this case, Othello's trust is completely misplaced and results in the death of so many people, that most of the people in the play end up killed, maimed, or injured.