It was first printed in 1623, and next July, Sotheby's will auction it off for a figure somewhere in the region of �?�3.7m to �?�5.2m. Sotheby's is excited at having such an important manuscript to sell and even goes so far as to say that this legendary first folio changed the world.

The auction house's English literature specialist, Peter Selley, says of Shakespeare that, "with the exception of the great spiritual leaders, his influence on western culture is more profound than any individual who has lived".

He terms the folio, "the most important secular book of all time."

And in many ways it could be true. Without it we would never have heard of Macbeth, Two Gentlemen of Verona, Twelfth Night, Julius Caesar, Winter's Tale, The Taming of The Shrew, Coriolanus, Anthony and Cleopatra, As You Like It, The Comedy of Errors, All's Well That Ends Well, and many other of his plays.

The first folio preserves 18 of Shakespeare's plays, including some of the most major which, if it weren't for the folio, would have been lost to the world.

You might say that you could get by very well without the plays, since many believe them complex and difficult to read, but you certainly can't get by without the phrases and philosophy contained in them. Whether we like it or not, Shakespeare has entered our language.

And not just for his well-worn phrases such as "to be or not to be, " but for more mundane ones which, without realising, we use every minute of the day.

When we say the world is our oyster, or that we can't tell what the Dickens someone's name is, or that the course of true love never runs smooth, or that someone has eaten us out of house and home, or that the better part of valour is discretion, we are quoting Shakespeare, albeit with little changes in syntax and wording from the original.

Our language is awash with similes, metaphors and exhortations which come straight from the bard's pen.

They crop up in all sorts of situations: as white as driven snow; laid on with a trowel; the wheel has come full circle; what's done cannot be undone; love is blind; thereby hangs a tail.

Other oft-used Shakespearean utterances that keep us going are, God save the mark; to kill with looks;

parting is such sweet sorrow; if music be the food of love, play on.

When you remind yourself not to gild the lily, or that nothing will come of nothing, or that someone is every inch a king, or more sinned against than sinning, you are quoting Shakespeare.

You are also quoting him when you say bag and baggage; bell book and candle; sharper than a serpent's tooth; the milk of human kindness; I have not slept one wink and I am sick at heart.

Self-help books, pop psychology and various counselling gurus have adapted the wisdom of Shakespeare's adages to suit their needs: neither a borrower nor a lender be; to thine own self be true; brevity is the soul of wit; be cruel only to be kind.

Politicians love to quote him too: some men are born great, some achieve greatness, and some have greatness thrust upon 'em.

Shakespeare's observations have become our observations.

We speak of people wearing their hearts upon their sleeves, of loving not wisely but too well, of jealously being a green-eyed monster. And whether we bear charmed lives or whether all the world's a stage or whether we kill with kindness, we can't stop using his phrases. The English language would have been so much the poorer without the bard.

The first folio is now considered the most important text in English literature.

Shakespeare made no attempt to have his plays published while he was alive and the folio was gathered together within years of his death by actor friends who had been part of the playwright's King's Men company and who wanted to see his genius preserved.

This is one of the rare surviving editions (750 were printed and only a third survive) and has been in Dr Williams's Library in London for the past three centuries, thus giving it one of the longest uninterrupted ownerships of any of the copies.

The library says it needs to sell it since it accounted for a third of the library's annual insurance bill and that its importance was such that it was a security risk.

And although there are questions raised about the rights of libraries to dispose of material that they are meant to preserve for present and future generations, Dr Williams's library is not the first to have parted with a copy - Oriel College, Oxford, sold its copy to the late Paul Getty in 2002.

Sotheby's defends its position in selling the book by pointing out that it is a piece of world literature and not confined to the UK.

It hopes that it will break its previous record of $6m for a first folio which was sold at a sale in New York four years ago.

Further acknowledging its international appeal, Sotheby's plans to take the book on a world tour, exhibiting it in Los Angeles, Chicago, Beijing, Hong Kong and other cities.

The Bible may be the most popular book in the world but it rarely sells for anything like what Shakespeare's first edition folio is expected to achieve next July.

IN THE SALESROOMS 16-20 April: Beckett, an exhibition of photographs by John Minihan, The Leinster Gallery, 27 South Frederick Street, Dublin 2 16- 30 April: sale of Russian Art, Magil Fine Art, 13A Bachelors Walk, North Quay Dublin 1 20 April: O'Reilly's jewellery and silver sale, 126 Francis Street, Dublin 8 (1pm) 23 April: Antique Fair, Clontarf Castle Hotel, Clontarf 25 April: Whytes Irish art sale, RDS, Dublin 4