His independence and initiative are shown in his choice of subjects. Although in "Dido" he took a standard theme of humanistic tragedy, and in the Henry VI plays and "Edward II" followed the prevailing taste for English history, and in "The Massacre of Paris" another fashion for the dramatization of current atrocities; yet in "Tamburlaine" he chose the story of a world conqueror, in "Faustus" a legend that had just entered print in the German "Volksbuch" of 1587, and in "The Jew of Malta" he worked over unknown sources into a tragedy of revenge with evident freedom of invention. All three stories present notable contributions to tragic themes, and the last two disregard both the fashion for historical subjects and the requirement that tragedy deal only with princes. These new and varied themes gave a chance for a considerable revolution in the content of tragedy. Revenge, murders, battles, intrigue, physical horrors are still prominent; but the Senecan round of incest and adultery disappears, and the "Mirror for Magistrates" no longer represents the epitome of tragic action. Marlowe's choice and treatment of plots seem, indeed, dictated by a new conception of tragedy, as dealing not merely with a life and death, or a bloody crime, or a reversal of fortune, but with the heroic struggle of a great personality, doomed to inevitable defeat. "Tamburlaine" is scarcely a tragedy at all, but rather a chronicle of the hero's greatness; but in "Faustus" and "The Jew" heroes with ambitions boundless and passionate like Tamburlaine's are overwhelmed in the end by the inexorable destiny of human weakness. In "Edward II," where the hero is less dominant over the action, the study of historical facts results in a more restrained, more human presentation of the same theme, a ruling passion drawing the protagonist to pitiful defeat.