John Mullan in The Guardian:
For a long time, the sedulous student who wants to see Shakespeare in the act of creation has been able to go to the extracts contained in the eight fat volumes of Geoffrey Bullough’s Narrative and Dramatic Sources of Shakespeare. Here you can find the stories that he pilfered and changed. You can see how he twisted two completely separate tales together to make The Merchant of Venice, for example, or decided to kill Lear and Cordelia at the end of King Lear when in his chronicle source both survived, or made Othello Desdemona’s murderer, when in Cinthio’s original Italian story, it is Iago who does the deed. The volumes give a dizzying sense of the playwright’s narrative dexterity as you see him extracting and welding together the elements from others’ narratives. Read John Kerrigan’s intense, condensed account of the playwright’s creative borrowing and the dizziness only increases. Focusing on a handful of plays, Kerrigan, one of the world’s leading Shakespeare scholars, shows that Bullough has recorded only the more obvious half of it. Kerrigan takes us beyond Shakespeare’s primary sources into the deeper texture of his allusions and passages of imitation. His originality, by this account, was largely a gift for the alchemical transformation of what he had read, heard recited, or remembered from his days on a hard bench at Stratford grammar school.
Kerrigan’s introduction ruminates about the meanings of originality, a concept unknown to critics before the later 18th century. Shakespeare inhabited a literary culture in which imitation of earlier models was applauded. Rhetoric (the Renaissance version of creative writing) approved of “invention”, but specified that this meant the clever combination of inherited elements. Yet Shakespeare is also different from his contemporaries: he is not showing off his literary knowledge but adapting narrative patterns and fragments of dialogue lodged in his memory. Kerrigan quotes Emerson observing that “All minds quote”; yet most of Shakespeare’s quotations – or inventive misquotations – would not have been spotted by his first audiences. A chapter devoted to Much Ado About Nothing reveals a play that is “pieced and patched and recycled” out of various Italian tales, its radical novelty a matter of the “piecemeal superflux” of reused materials.