We are not dealing with folklore. Folklore is rigidly conservative, and in it incidents have a fixed, unalterable shape. When story has once emerged out of the stage of folklore into that of romance the conditions are different; the romancers select, combine, and transfer quite freely.
In Diu Krone the challenger is a shape-shifter, as in Sir Gawain ; but it does not follow that one borrowed from the other, for in medieval romance almost any stranger may prove to be a shape-shifter. The author of Sir Gawain would assuredly not be dependent on a particular romance for a knowledge of shape-shifters, or green men (green being the fairy colour), or enchantresses, or magic laces, or faery chapels. It is, indeed, quite likely that the poet found one, or both, of the two main incidents in French romances and borrowed them in the same way that Shakespeare borrowed many of his plots. But the quality of the poem itself is good evidence that he had sufficient genius to use his materials with a poet’s imagination.
It is very rarely that we find such artistic unity in a medieval romance as in Sir Gawain , and only consummate art could have achieved it. The two incidents, the Beheading and the Wooing, are no longer disconnected themes; they are vitally linked together. The test of Gawain’s courage and the test of his chastity are revealed as one and the same; the same man “wrought them both,” under the spell of the same malicious enchantress. In medieval theory only virtue can defeat enchantment; and had not Gawain been proof against the lady’s wiles which tempted his chastity, the beheading which was to test his courage must (so it appears in the event) have been fatal to him.
The writer was a true poet. Out of the raw material of folklore and the elements of crude magic he has conceived a human story with human motives, without sacrificing anything of the real magic which is the atmosphere in which his story lives.