Now that hordes of people are leaving the Catholic Church, eight noted Catholics explain why they're staying--and most of them give creditable performances. Their tone is intimate, wry, relaxed, and just a bit nostalgic. Gone are the polemics and apologetics of the Fifties, the trauma and vision of the Sixties. Sidney Callahan admits she misses Mass and doesn't pray regularly. ""I recognize that I am a mediocre Christian, but that God loves me anyway and can make use of me."" John Deedy talks about passing through the stages of literal Catholicism, formalist Catholicism, and activist Catholicism, only to find himself in the end at a point ""where I prefer a private and complacent Catholicism."" Andrew Greeley, in what is perhaps the best piece of all, writes with ill-concealed bitterness of his disillusionment with the institutional Church, but then dismisses his personal feelings as irrelevant. ""Leave it?"" he concludes, ""No way."" Editor Delaney's only mistake was inviting theologians to his little party. James Hitchcock and Richard McBrien succumb to their professional instincts and begin to lecture. Worst of all, Bishop Fulton J. Sheen, in his eighties and still going strong, rushes out and overwhelms the reader with one of his patented high-powered sermons, designed to show why you should be Catholic. Apart from that disconcerting reminder of the old days, this is an agreeable collection of sophisticated, sadder-but-wiser believers kicking off their shoes and speaking their minds.