To Seneca and the false Aristotle created by the humanists from the _Poetics_, the precepts of Horace, the definitions and maxims which sifted down through the encyclopaedists of the Middle Ages, and the example of Seneca, not only the men of the Renaissance but even we of today owe some of our most cherished ideas concerning tragedy. First of all, perhaps, is the belief that tragedy must end unhappily. The Greeks--whether creators or critics--had no such theory. It was enough for Sophocles and Aristotle that tragedy should be serious in theme and dignified in characters and in language. In the second place, we ordinarily believe that a tragedy should have five acts, and many of us can draw a diagram to prove it. Shakespeare and his fellows seem to have been dominated by the same theory, difficult as they sometimes found it to observe. The sacred unities, dominant so long in Italian and French tragedy, though never observed in any English play more notable than Addison's _Cato_, we have learned to disregard and even to decry, though such an attitude in the Elizabethan age awakened the censure of Philip Sidney and doubtless required some hardihood or even recklessness. The chorus also we have long since abandoned, but Greene and Peele and Kyd and Marlowe and Shakespeare and others of their time used it more than once and with good effect. They even, in some instances, combined with it the ghosts and infernal spirits, which beyond a doubt they owed to Seneca, and made this unearthly chorus, not only the commentator, but in some sense the subtle director of the action. Perhaps the most refined form of this is to be seen in the Ghost in _Hamlet_, who, though he does not appear technically as Chorus, yet recalls by his original incitement of the action and his later intervention to renew and direct it, as well as by his language and his attitude, the ghosts of Tantalus, Thyestes, Laius, and Agrippina in Seneca, and the spirits of Andrea and Revenge in _The Spanish Tragedy_. It is perhaps not going too far to find in the dream-setting of Hauptmann's _Elga_ some reminiscence of Shakespeare's _Taming of the Shrew_ and Greene's _James IV_, and consequently, in a remote sense, of Seneca's introductory figures, Tantalus, Thyestes, and the rest. But these matters and the striking resemblances in situation and in utterance cited so abundantly by Cunliffe and by Munroe (_Journal of Philology_, Vol. VI, pp. 70-79), though they could be increased by many passages in _Macbeth_ and _King Lear_ as well as in the plays of other dramatists than Shakespeare, are after all not fundamental. Some other features that seem fundamental may be noted.