Geoffrey Chaucer is the most receptive as well as the most inventive English poet of the Middle Ages. It has been said of Shakespeare that he was ‘a snapper-up of unconsidered trifles, hoarding like a magpie what others did not value, and transmuting it, at opportune moments, into dramatic gold’.1 This could hardly have been Chaucer’s way. The medieval poet prized learning more than originality and he was more likely to flaunt his reading than to disguise it. Chaucer habitually plays down his own, individual share in his writing, disguising rather than parading his inventiveness. And yet there is something Shakespearean in the way he defies being pinned down to definite sources. It is instructive in this respect to compare the existing collections of sources of the two poets, e.g. The Sources and Analogues o f Chaucer’s Canterbury Tales1 and Narrative and Dramatic Sources o f Shakespeare.3 Both are admirable and very useful anthologies of otherwise not easily accessible texts, but they do not provide ‘sources’ in a strict sense of the word in as many instances as one might expect. Chaucer can be a very faithful translator when he chooses, as with Boethius’ Consolatio Philosophiae or the Roman de la Rose, but whenever he embarks on works of his own he can hardly take over a single line from one of his sources without subtly changing and adapting it to his unorthodox design. He is anything but an uncritical reader, though he often likes to portray himself as one.