The character of Iago in Shakespeare’s play, Othello, has greatly puzzled critics over die past century, and much controversy has centred around the motivation behind his hatred of Cassio and Othello. The intensity of his emotion and the fiendishness of his actions seem to many critics completely disproportionate to the causes of resentment which Iago declares to be his motives. This puzzlement is, at least, partly caused by failure to recognize and appreciate the nature of sin in the Christian sense of the word. Critics would cease to wonder at the extent of Iago’s moral depravity if they were willing to take seriously those Christian teachings on personal sin and its destructive effects on human nature which still formed a living part of western man’s intellectual equipment in the fifteenth century. Shakespeare’s dramatic analysis of the effects of sin on Macbeth afford one, though not the only, example of how well he understood them. His delineation of Iago is another. In many ways, indeed, Iago constitutes an excellent illustration in dramatic form of St Thomas’ teachings on sin, as well as those on the special sins of pride and envy and on the Devil.

As so many critics have insisted, the specific instance of wounded pride which Iago alleges as the source of his bitterness certainly does not of itself suffice to explain the vicious extremes to which Iago’s malevolence finally carried him. As St Thomas teaches, however, the elements in the immediate occasion of any sin seldom account in themselves for all the evil which ultimately will flow from the sin.