I should by now know better than to think of religions as family trees, but when a student asked today what the difference between "Catholic" and "Christian" was I turned horticultural again. I wanted to show that "Christian" was a term used by scholars (and some Christians) to refer to the whole family, while others - a branch of the tree - used "Christian" only for themselves. That things weren't going to work became clear at latest when I found myself representing Pentecostalism as a branch floating free above the tree, which of course some of the self-described "Christians" would, too... at which point I felt obliged to acknowledge that Catholics would represent the tree differently, too. Oy vey!