There's nothing that says that these columns are supposed to be read once, and then forgotten. On the other hand, with the amount of reading material that we find ourselves inundated with, it's hard to think of some other way of dealing with them (other than not reading them at all). But this is, of course, the internet, and these columns don't sit on our shelves, or get deleted when we have to make room in our filing cabinets. They're right here on this site, and nothing is stopping us from rereading a column. It happens to me occasionally - especially when I'm checking up on myself, trying to discover to what an extent the idea behind an upcoming column rehashes material that I've used in previous columns. And though sometimes I find that I have to be careful because I really have previously tred on the same territory, sometimes these searches bring me to columns which I read through as though for the first time and exclaim to myself that it's both interesting and well written. Hey! Maybe I should send mail to myself telling me that.