They help to identify communities and factions, and provide convenient targets for 'the other side' to attack. That is the context of the bizarre spat in the Northern Ireland assembly this week, in which hardliners of the Democratic Unionist Party DUP forced an emergency debate over - a display of Easter lilies. It was, many might think, a ridiculous waste of time and energy. But it is also possible to argue that the debate provided a telling insight into the current state of the peace process. The republicans of Sinn Fein knew exactly what mischief they would stir up when they persuaded the cross-party committee responsible for such things to bedeck the main hall of the Stormont assembly building with lilies.
Lilies are the universally recognised symbol of mourning.
For Christians, they have an especial significance at Easter. But for Irish republicans, they commemorate the dead of the 1916 Easter Rising, bloodily put down by British soldiers. Every year at Easter, there are republican marches and rallies in memory of the dead, and bellicose speeches pledging revenge. The lily features prominently on such occasions, usually in the form of a little oblong paper version, worn on the chest. One of the curiosities of the early years of the Troubles was that the emerging Provisional IRA and its supporters favoured fixing their paper lilies with pins, while the old Official IRA preferred a gummed version.