The first thing you hear from him is a complaint: He's talking, but the other guy isn't listening. The last thing he does is announce he's not going to talk any more. Between that first " 'Sblood, but you will not hear me" and the final "from this time forth, I never will speak word," Iago is the instigator of three deaths and much other ruin. Why does he do it? Coleridge famously called Othello's villain a creature of "motiveless malignity" but it seems to me his reasons are clear as a map. Iago is one of those people in life who feel they have a gallon to give, but the world only took a cup: He gives the lie to the comforting belief of successful people that they are where they are for good reasons. It's a rationalist myth—that our instruments for testing and evaluating people really cull those who are objectively superior from the ranks of those who are objectively less able.
Iago is enraged by the way the sources of success—opportunity, charisma, sexiness, social networks, and especially the attention of the world—are unfairly given. His plot against this world order is a disappointed man's scheme, a petty bureaucrat's game. He's a colorless, uninteresting man in a dull job; no one pays much attention to him. That, he recognizes, is his chance. He isn't one of the large-gestured and much-fulfilled people who stride confidently through the world, but he sees that now and then those people are caught in the narrow circumstances where he—where most people—have to work. He's like a worker who deliberately leaves a coupling or two loose in the plumbing of that house he can't afford. Or those New Orleans cops who, when Nicholas Cage dared them to arrest him, decided: Screw it, we will. Iago has a little power, and he uses it to get revenge on people with more. Because he knows they aren't in their places for good and just and rational reasons, but rather because of luck.
A number of people lately have warned me off the phrases "post-rationalist" and "after thought," on the grounds that all thinking has rational and irrational aspects, and that "thought" is not a word that should be limited to syllogisms and explicit debates based on reason. Everything the brain does to perceive, assess and respond to the world is "thought," as the evolutionary biologist David Sloan Wilson emailed to me. This is true, but I meant "post-rationalist" to describe a new kind of society, not a new kind of person. People are and always have been an amalgam of reason and unreason. Only in the past three centuries, though, and only (at first, anyway) in the peninsular extreme of Eurasia called Europe, have there been societies that rested the notion that reason can make the instruments that organize society. From the dawn of modernity, Iago denounces our intelligence tests, competitive exams, performance reviews and other embodiments of rationalist myth.