  == Cleanup attempt ==  OK, I have just given this a pretty serious overhaul, keeping in mind comments on this talk page. I believe I have covered most of the major concerns. However, it is far from complete. At this point, I think a casual reader would get a general sense of the concept and its different uses. I have added citations wherever possible, and I'd like to see more published sources for quotations. Please feel free to make additions or suggestions, but let's try to keep this from becoming unreadable. Thanks to all whose suggestions on this page were incorporated into this iteration.  