I grew up Protestant in the Northeastern U.S., in an area with many Irish and Italian families, so most of my playmates when I was in elementary school were Catholic. This was somewhat (ahem!) before Vatican II, and both Protestant and Catholic kids were taught by their parents (and sometimes even in Sunday School) to regard the other with suspicion, if not downright hostility. My Catholic playmates, for instance, said they were told they would spend eternity in Hell if they (literally!) so much as set foot inside a Protestant church building. Boy, have things changed. While there are...