Last year, two computer scientists devised an algorithm to establish the most important people in the whole of human history. In fourth place, behind Jesus, Napolean and Muhammad, was William Shakespeare. The accolade is yet another entry to what is already a substantial list – ‘Greatest Briton’, ‘Millenium’s Best Writer’, ‘UK’s Greatest Cultural Icon’ – cementing his status as the greatest writer who ever put pen to paper. For as we celebrate Shakespeare’s 450th birthday today, few could dispute that the enormity of his legacy and the hold he has since exercised over our imagination has been of an unquantifiably supreme level.

As is the case with most legendary personages, Shakespeare’s life is relatively shrouded in mystery. Raised in Stratford-upon-Avon, the playwright and dramatist worked as an actor in London before writing for a playing company, Lord Chamberlain’s Men. It was this troupe that first performed the classic works – the tragedies of King Lear and Othello, the comedies of Twelfth Night and Much Ado, the histories of Henry V and Richard II – that, among many others, have spawned centuries of captivated imaginations.

Patrick Stewart as Macbeth and Kate Fleetwood as Lady Macbeth, Gielgud 2007

Indeed, Shakespeare may still be outsold by the Bible, but the fascination of his art has made him a Lord in his own right. One would be hard-pressed to find an individual ignorant of Juliet’s ‘wherefore art thou Romeo!’, a writer uninspired by Macbeth’s ‘Tomorrow and tomorrow and tomorrow’, a stage unfamiliar with Hamlet’s ‘To be, or not to be’. To artists, directors and audiences, Shakespeare’s output provides an inspiration that is inexhaustible, timeless and all-encompassing, and ultimately begs the question: how does this man, born in 1564, still manage to speak so many volumes, to so many people, after so many centuries?

One reason might be his inventive command of language. Perhaps without us realising, Shakespeare’s flair for words has gradually shaped the English language over time. He coined hundreds of expressions and phrases that we now use in everyday speech – next time you describe yourself as ‘being in a pickle’, ‘being cruel to be kind’ or tell a ‘Knock knock! Who’s there?’ joke, you’re quoting directly from the Bard. But on a more profound level, the language of his deepest soliloquies effortlessly manages to conjure the darkest, liveliest or most poignant of emotions – note the power of Shylock’s ‘Hath not a Jew eyes?’ or Lady Macbeth’s invocation of evil, ‘Make thick my blood.’

Undoubtably another factor is that the more open-ended, malleable essence of drama has enabled the various mediums of theatre, television and film to reinvent Shakespeare over time. Actors, directors and producers have had free reign to leave their own imprints on plays which lend themselves very well to reinterpretation and speak to us with as much relevance as when they were written. In 2012, the RSC had a production of The Merry Wives of Windsor set in a recognisably contemporary context with modern dress, and a recent adaptation of Love’s Labour Lost saw the setting transported to a modern day reality TV show.

Alexandra Gilbreath and Desmond Barrit in The Merry Wives of Windsor, RSC 2012

But perhaps the most pertinent answer to the question of Shakespeare’s success is his a very insightful understanding of human nature. His variety of plots and characters reflect the authentic way in which humans think, feel and behave; in this sense, there is not a single person in the world who cannot relate in some way to one of his characters. As expressed by Sir Trevor Nunn, ‘Shakespeare has more wisdom and insight about our lives, about how to live and how not to live, how to forgive and how to understand our fellow creatures, than any religious tract.’ Watch one his plays and observe how.

Of course, whichever of these factors accounts for our own admiration, we can all agree that Shakespeare’s genius remains unrivalled 450 years later. With the launch of the digital project myShakepeare, the RSC recently teaming up with Google’s Creative Lab to broadcast plays in real time, and an exciting line-up of upcoming productions, Shakespeare’s legacy shows no signs of abating. As Samuel Johnson said of the playwright, he was ‘not of a time, but for all of time’.