This habit of thought, useful as an antidote to extravagance, was not fertile as a motive of dramatic production. Addison worked with strict and conscious attention to his critical principles: the consequence is that his _Cato_, though superficially "correct," is a passionless and mechanical play. He had combated with reason the "ridiculous doctrine in modern criticism, that writers of tragedy are obliged to an equal distribution of rewards and punishments, and an impartial execution of poetical justice."[54] But his reasoning led him on to deny that the idea of justice is an essential element in tragedy. "We find," says he, "that good and evil happen alike to all men on this side the grave; and, as the principal design of tragedy is to raise commiseration and terror in the minds of the audience, we shall defeat this great end if we always make virtue and innocence happy and successful.... The ancient writers of tragedy treated men in their plays as they are dealt with in the world, by making virtue sometimes happy and sometimes miserable, as they found it in the fable which they made choice of, or as it might affect their audience in the most agreeable manner."[55] But it is certain that the fable which the two greatest of the Greek tragedians "made choice of" was always of a religious nature, and that the idea of Justice was never absent from it; it is also certain that Retribution is a vital element in all the tragedies of Shakespeare. The notion that the essence of tragedy consists in the spectacle of a good man struggling with adversity is a conception derived through the French from the Roman Stoics; it is not found in the works of the greatest tragic poets. This, however, was Addison's central motive, and this is what Pope, in his famous Prologue, assigns to him as his chief praise: "Our author shuns by vulgar springs to move The hero's glory or the virgin's love; In pitying love we but our weakness show, And wild ambition well deserves its woe. Here tears shall flow from a more generous cause, Such tears as patriots shed for dying laws: He bids your breasts with ancient ardour rise, And calls forth Roman drops from British eyes. Virtue confessed in human shape he draws-- What Plato thought, and godlike Cato was: No common object to your sight displays, But what with pleasure heav'n itself surveys; A brave man struggling in the storms of fate, And greatly falling with a falling state."