Before human aggression became a major concern of the behavioral sciences, it had long been the subject of philosophical speculation, and hypotheses about what the Christian theologians referred to as &dquo;the problem of evil&dquo; go back to the taproots of Western culture.Aristotle, for instance, took a balanced view of the subject, treating human aggressiveness as innate but controllable: &dquo;Man, when perfected, is the best of animals; but if he be isolated from law and justice he is the worst of all [...] If he be without virtue, he is a most unholy and savage being.&dquo; Some philosophers have taken a more dour view, however. Writing in the cut-throat atmosphere of Renaissance Italy, Machiavelli argued that: &dquo;All those who have written upon civil institutions demonstrate [...] ] that whoever desires to found a state and give it laws, must start with assuming that all men are bad and ever ready to display their vicious nature.&dquo;In recent decades, the argument about human violence has been taken over by the behavioral scientists, and three major alternative explanations have been advanced over the years -the so-called &dquo;biological-instinctual&dquo;, &dquo;social learning&dquo; (or &dquo;socio-behavioristic&dquo;) and &dquo;frustration-aggression&dquo; hypotheses 1.The biological-instinctual hypothesis, tracing its heritage to Freud, postulates an instinctive aggressive drive, or appetite. As Freud wrote: &dquo;A powerful measure of desire for aggression has to be reckoned as a part of man's instinctual endowment [...] Homo homini lupus; who has the courage to dispute it in the face of all the evidence in his own life and history ?&dquo; More recent-* This article was be prepared with the partial support of NIMH Training grant