In William Shakespeare's play Othello, Iago (addressing Roderigo) promises that he will never
wear [his] heart upon [his] sleeve
For daws to peck at: I am not what I am. (1.1.64-65).
In other words, he explicitly informs Roderigo that he will never show his true emotions openly (“wear my heart upon my sleeve”). If he did so, “daws” (i.e., jackdaws, proverbially foolish birds, and thus symbols of human fools) would be able to “peck at” his heart and emotions. He will never make himself vulnerable in this way.
This declaration is just one of several assertions in Iago’s early speeches to Roderigo in which he reveals that he plans to be a hypocrite – that he plans to deceive Othello while pretending to be loyal to Othello. If he were to make plain to everyone just how much he really hates Othello (if he were to wear his heart upon his sleeve), then he could not successfully deceive and harm Othello. Iago plans never to make that mistake. The only way Iago can destroy Othello is by deceiving not only Othello, but everyone else as well.
Part of the irony of this declaration, of course, is that Roderigo never realizes the relevance of these lines to his own relationship with Iago. It never seems to occur to Roderigo that if Iago is capable of deceiving Othello and willing to do so, he is also capable of deceiving Roderigo. Ironically, Roderigo himself is precisely the kind of foolish “daw” that Iago speaks of with such contempt. Renaissance theories of friendship taught that no person could be a good friend unless s/he was first a good person. Iago is here revealing openly to Roderigo that he is not a good person. Roderigo should realize, then, that Iago also cannot be a good friend, either to Othello or to Roderigo.
When Iago says “I am not what I am,” he means that he is not truly and in essence what he merely pretends to be. He pretends to be a servant of Othello, but he is really a servant of himself. He is a hypocrite, a liar, a deceiver; he is not the loyal lieutenant and good friend that he pretends to be. Iago here alludes blasphemously to Exodus 3:14 in the Bible, where God says “I am what I am.” Iago’s willingness to toy in this way with Biblical phrasing proves the depth of his pride, effrontery, and contempt for virtue. Once again, if Roderigo were not such a fool, he would realize that anyone who is able to allude to the Bible in such a disrespectful fashion is not a person to be trusted.
Iago is such a fascinating character, in part, because he openly and immediately declares his evil nature and his evil plans, and then he methodically goes about putting those plans into highly effective action. We, in the audience, can only sit back and watch in horror as he achieves one of his previously announced objectives after another.