Shakespeare inhabited a literary culture in which imitation was applauded. This erudite study teases out his alchemical transformations of what he had read or seen

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.

The book is unrepentantly erudite, but the erudition is as diverting as it can be daunting

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. You will have to read slowly – and maybe Google – to understand the variety of materials (Ariosto, Matteo Bandello, Luigi Pasqualigo) that go into this nearly tragic comedy. The reward is a vivid sense of how original it was to borrow.

Traditional assurances that Shakespeare knew next to nothing of Greek tragedy are upended in an analysis of King Lear and its relationship to Sophocles’s two Oedipus plays. Shakespeare had access to these via widely available Greek/Latin parallel texts (we should take with a pinch of salt Ben Jonson’s aspersions about his “small Latin and less Greek”). In particular, he found his way back to Greek tragedy via Seneca’s Latin versions of Greek originals. The scene on Dover Cliff, where the blind Gloucester thinks he has been led by Edgar, the son he does not recognise, has its “original” in Seneca’s Phoenissae, where Antigone leads Oedipus in search of a convenient precipice. “Layers of imitation resonate back to antiquity.”

So you know the story of Othello? Even the version where Desdemona is killed with a stocking? Read more

In his final chapter, Kerrigan tackles one of the few Shakespeare plays supposed to have no specific source, The Tempest. He finds here not only echoes of contemporary writing about the colonisation of Virginia and Bermuda, but also the reuse of sentiments culled from Virgil’s celebration of the powers of agriculture, his Georgics. Where Shakespeare is supposed most natural he is in fact most literary.

The book is unrepentantly erudite, but the erudition is as diverting as it can be daunting. There are digressions into men’s hairstyles in Renaissance England (essential to some of the jokes in Much Ado), contemporary agricultural experiments (ditto The Tempest), or manners of walking on the stage (where actors strutted or “jetted” or jigged or “tripped” or – like Richard III – balefully limped). The chapter on Much Ado, a play in which a servant almost triggers a tragedy by dressing up as her mistress, traces its reliance on contemporary publications about fashionable dress. Elizabethan England still had sumptuary laws, placing stern limits on the wearing of luxurious apparel. “Actors were an affront to these rules,” elaborate costuming being one of drama’s essential resources. How exciting it was to see someone flagrantly dressed in the wrong clothes!

The four main chapters began as lectures, and Kerrigan clearly expected his listeners to concentrate hard. He is confident he can use words such as “sticomythic” and “haruspication” without further explanation, that Euripides and Virgil are our familiars, and that the plot details of Shakespeare’s plays are hardwired in our heads. The text bristles with endnote numbers, taking the reader – if he or she wishes – to a compendium of Shakespearean lore at the back of the book. But the trust in our literary curiosity is intoxicating. Who wants Shakespeare to be made easy when he was so beautifully and originally complex?

• Shakespeare’s Originality is published by Oxford. To order a copy for £25 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.