As a non-binding dialogue between representatives of completely unrelated faiths, this week's Millennium World Peace Summit is by no stretch an ecumenical council. However, it got me thinking, what exactly is an ecumenical council, and when was the last one held? Not surprisingly, the answer to both questions depends on one's perspective.By way of definition, my handy Oxford Dictionary of the Christian Church (which insists on "oecumenical") says they are "assemblies of bishops and other ecclesiastical representatives of the whole world whose decisions on doctrine, cultus, discipline, &c, are considered binding on all Christians."Key in on "whole world" and "binding." At best, "whole world" meant whichever invited parties were willing and able to make the trip; it later shrank to "whole Western world" (beginning with the Fourth Council of Constantinople, 869) and "whole Roman Catholic world" (beginning around the Council of Trent, 1545-1563). "Binding" is also slippery. Protestants tend to consider the councils and their rulings binding only insofar as they stick to Scripture. Some Catholics wouldn't be bound either: the 1409 Council of Pisa lost its bid to make the all-time list when neither of the men claiming to be pope obeyed it. Ecumenical councils trace their lineage back to the First Council of Nicea (325), which is most famous for giving us the Nicene Creed (which is considerably shorter than the version we often recite), and being called by Emperor Constantine. Of the 1,800 or so bishops he invited, fewer than 400 came; nonetheless, this was considered a quorum, and the authority of the council has never been seriously questioned. Oddly enough, one of the bishops who didn't make it was the bishop of Rome, Sylvester ...