the guy who convinced me to be an it in the first place, bertrand russell.t was obvious, everybody knew it. and then on my next page was about how the babylonians then invented the 360-degree angle. now, how did i know that? because it was in the encyclopedia britannica, it was in bertrand russell's history of philosophy, it was everywhere. so i was about to write that, and then i thought, oh, my god, if eric's going to read this book, i want eric to feel what it's like to be a babylonian b. and to feel what it's like, i have to put the babylonian protractor in your hands and to make your feel viscerally what it's like, i have to find out whether that protractor is made of clay, wood or copper. so for a month i pursued the question of whether a protractor is made of clay -- that is, a babylonian protractor -- is made of clay or p copper or wood. and i couldn't find it. and if somewhere in the back of my mind this happens to you every day, this happens to authors too, you go, you amazing idiot, how could you be so stupid? you are following up this obsession.