The specific emphasis and character of tragedy has changed in different periods. In classical tragedy, the protagonist usually suffers through fate interwoven with human interests and passions (as in Sophocles' Oedipus the King [ca. 428 B.C.]). (See Catharsis and Hamartia for details on Aristotle's theory of tragedy.)
In the Middle Ages, tragedy was associated with the downfall of eminent people through the inevitable turning of Fortune's wheel; their fall exemplifies the inconstancy of Fortune and the folly of placing trust in worldly goods rather than God's will (Chaucer's "The Monk's Tale" [ca. 1387] lists several such exempla).
Renaissance tragedy in England was flexible both in its willingness to combine tragic and comic modes, and in the attributes of the tragic protagonist. Thus it was criticized by Aristotelian critics such as Sir Philip Sidney for "mingling kings and clowns" and arousing laughter at "sinful things" (An Apology for Poetry [1583]); for instance, the fallen King Lear has a Fool for his companion, and the sinister Iago invites laughter at the ease with which he deceives Othello. English dramatists and their audiences were fascinated by sympathetic or admirable villains (contrary to Aristotelian principles of tragedy), and one of the most popular dramatic forms was the revenge tragedy, such as Hamlet (1600).
Since the eighteenth century, most tragedy has dealt with characters from the middle or lower classes ("domestic" or "bourgeois tragedy"). The protagonists suffer from commonplace misfortunes or their own inescapable mediocrity (like Salieri in Peter Shaffer's Amadeus [1980]). In Eugene O'Neil's The Iceman Cometh (1939), the characters are all social failures consoling themselves with whisky in Harry Hope's bar. They illustrate the need for illusions to make life bearable when one cannot succeed by the competitive and materialistic values of capitalist society.