'Right,' I said, nodding energetically and trying to determine whether any of the rectangles in my peripheral vision was a box of tissues. Unfortunately, they were all books. The professor was talking about the differences between creative and academic writing. I kept nodding. I was thinking about the structural equivalences between a tissue box and a book: both consisted of slips of white paper in a cardboard case; yet - and this was ironic- there was very little functional equivalence, especially if the book wasn't yours. These were the kinds of things I thought about all the time, even though they were neither pleasant nor useful. I had no idea what you were supposed to be thinking about.