Few, if any, of the great masterpieces of literature, even of those which bear the most unmistakable imprint of an original mind, are 'original' in the vulgar sense of being invented 'all out of the head' of the author. Most frequently they are the development and the sublimation of forms and subjects already current; for, as Dumas pere truly said, it is mankind, and not the individual man, that invents. The wagon of Thespis preceded the stage of AEschylus, while Thespis himself had predecessors who did not even adopt the wagon. The great dramatic schools of all periods took the greater and better part of their themes from the myth, history, or fiction current in their day. So it has been with most other kinds of literature, and to this rule the Commedia of Dante, though one of the most truly original creations of the human mind, forms no exception. The main subject of the poem, the visit of a living man, in person or in vision, to the world of the dead, and his report of what he had seen and heard there, belongs to a class of world-myths than which few are more widely distributed in place or time, and none have been more fortunate in the place won for them by the masters of literature. After occupying an important place in several of the antique religions it afforded subjects to the genius of Homer, Plato, and Virgil; it was then adopted into the early Christian Church, and afterwards constituted one of the favourite subjects in the popular literature of the Middle Ages, until, finally, Dante exhausted the great potentialities of the theme, and precluded all further developments."