I have a letter from a friend, dated April 2006, that I still have not answered. I mean to answer it; I fully intend to answer it. I actually have answered it, several times, in my head. The letter I have written in my head is a great letter, as letters-written-on-the-mind often are. The letter in my head is so perfect I fear that trying to get it down on paper would dilute it, diminish it, ruin it. I'm writing you a letter, I say to my friend. I assure her that it will be a great letter. I compose another sentence, mentally, change a word here and there. Just wait, I tell her. Your letter is coming.