Patrick Kavanagh, one of Ireland's great poets, once said: "No man can adequately describe Irish life who ignores the GAA."
By James Helm
BBC News, Dublin
For all the dramatic changes in Irish society over the last decade or so, the Gaelic Athletic Association (GAA) remains a powerful force, with around 750,000 members at more than 2,000 clubs.
Croke Park is now an ultra-modern 80,000-seater stadium
The organisation runs Ireland's two most popular sports, Gaelic football and hurling, both of which are amateur.
The clubs are a vital part of the very fabric of Irish communities.
In towns across the country, and in Catholic communities in Northern Ireland, the GAA club is a busy social hub as well as a sporting centre.
Micheal O'Muircheartaigh is the golden voice of Gaelic games, Ireland's best-known commentator, who has been reporting on matches for more than 50 years.
He describes the GAA simply as "part of what we are".
The headquarters of the sports is Croke Park, the hugely impressive stadium on the north side of Dublin, which holds 82,000 fans.
It was here, in 1920, that the British Army fired into the crowd, killing spectators and players.
The Hogan Stand was named in memory of one of those who died on what became known as "Bloody Sunday".
A two-thirds majority is needed to pass the motion
The GAA grew up as an expression of Irish culture.
Up until 1971, any member caught playing, or even watching, "foreign games" such as soccer or rugby, could be banned or suspended.
Under its Rule 42, other sports are not permitted to be played on GAA grounds, including Croke Park.
Pop groups have performed there, and Muhammad Ali once fought at "Croker", as it's affectionately known, but those "foreign games" have never been allowed on to the hallowed turf.
The issue of opening up Croke Park to other sports has been debated for years, but the issue has now come to a head.
That is because Lansdowne Road - the dilapidated home to Ireland's national rugby and soccer teams across town - is soon to be redeveloped.
While it is being re-built, those sides will be homeless, and may have to look to Cardiff, Glasgow, or elsewhere for temporary accommodation.
For many supporters of a change to Rule 42, including Micheal O'Muircheartaigh, it would be a shame if Irish teams had to travel abroad to play "home" games.
They say it makes financial sense to open the stadium up to rugby and soccer, and that a global audience should be allowed to see the GAA's greatest gem.
GAA President Sean Kelly is in favour of the change
Those who favour the status quo ask why the GAA, with its amateur players, and whose members built Croke Park, should have to help out wealthy, professional organisations.
And they argue that sports such as soccer and rugby are in direct competition with Gaelic football and hurling in towns across Ireland.
Tom O'Riordan, a GAA member in a club south of Dublin, said: "We're in the business of trying to promote our games and there are other sports trying to promote theirs. Why should we give them our shop window to advertise?"
Irish Prime Minister Bertie Ahern, an avid sports fan, has made plain his desire to see Croke Park opened up.
The change has been rejected in the past, and a two-thirds majority vote is needed at the GAA Congress taking place at the stadium itself.
The Ulster counties oppose the change, but a majority are in favour. Most are agreed: the result is likely to be close.