I suppose that if you feel that you cannot invite everyone who is a bishop with jurisdiction to Lambeth in 2008 and if you feel the need to choose who will be invited and who will not, the criteria had better be simple, consistent and easy to comprehend. Some are not sure that this standard has been met.
I'd like to offer a humble suggestion.
Actually, it's not my idea. It comes from a cartoon by Tom Cheney that was published in a recent New Yorker, which seems to me to offer as simple and coherent criteria as any I've seen.
(I can't reprint the actual cartoon on this blog because it's copyrighted, the New Yorker doesn't seem to like people who blog their artwork, and I can't afford a lawyer. You can, however, see it here and, if you like, buy it as a t-shirt.)