The Plays used by Shakespeare.—Although Shakespeare made up one of his plots, the Comedy of Errors, from two plays of Plautus (254-184 B.C.), the Menaechmi and Amphitruo, the rest of the plays he used for material were contemporary work. He borrowed from them plots and situations, and occasionally even lines. With the exception, however, of one of the early histories, the plays he made use of are in themselves of no value as literature. Their sole claim to notice is that they served the need of the great playwright. None but the student will ever read them. In practically every case Shakespeare so developed the story that the fiction became essentially his own; while the poetic quality of the verse, the development of character, and the heightening of dramatic effect, which he built upon it, left no more of the old play in sight than the statue shows of the bare metal rods upon which the sculptor molds his clay.
Seven histories go back to the earlier plays on the kings of England. The Second and Third Parts of Henry VI are taken from two earlier plays often called the First and Second Contentions (between the two noble houses of York and Lancaster). The First and Second parts of Henry IV, and Henry V, are all three an expansion of a cruder production, the Famous Victories of Henry V. Richard III is based upon the True Tragedie of Richard, Duke of York; King John upon the Troublesome Reigne of John, King of England, the latter undoubtedly the best of the sources of Shakespeare's Histories.
King Leir and His Daughters is the only extant play which is known to have formed the basis of a Shakespearean tragedy. Shakespeare made additions in this case from other sources, borrowing Gloucester's story from Sidney's Arcadia. The earlier play of Hamlet, which it is believed Shakespeare used, is not now in existence.
Among the comedies, the Taming of the Shrew is directly based upon the Taming of a Shrew. Measure for Measure is less direct, borrowing from George Whetstone's play in two parts, Promos and Cassandra (written before 1578).
The existence of versions in German and Dutch of plays which present plots similar in structure to Shakespeare's, but less highly developed, leads scholars to advance the theory that several lost plays may have been sources for some of his dramas. Entries or mentions of plays, with details like Shakespeare's, dated earlier than his own plays could have been in existence, are also used to further the same view. The Two Gentlemen of Verona, the Merchant of Venice, Romeo and Juliet, Hamlet, and, with less reason, Timon of Athens, and Twelfth Night, are thought to have been based more or less on earlier lost plays.
Finally, a number of plays perhaps suggested details in Shakespeare's plays. Of plays so influenced, Cymbeline, The Winter's Tale, and Henry VIII are the chief. But the debt is negligible at best, so far as the general student is concerned.
To conclude, what Shakespeare borrowed was the raw material of drama. What he gave to this material was life and art. No better way of appreciating the dramatist at his full worth could be pursued than a patient perusal and comparison of the sources of his plays with Shakespeare's own work.
The best books on this subject are: H. E. D. Anders, Shakespeare's Books (Berlin, 1904); Shakespeare's Library, ed. J. P. Collier and W. C. Hazlitt (London, 1875); and the new Shakespeare Library now being published by Chatto and Windus, of which several volumes are out.