Sorry! Don't know. I thought probably his autobiography, but I've just searched a PDF of that, and his History of Western Philosophy, and it's not in either o

Sorry! Don't know. I thought probably his autobiography, but I've just searched a PDF of that, and his History of Western Philosophy, and it's not in either of those. I guess one of his essays - must be one of the ones collected in books, because those are the only ones I've read, but that doesn't narrow it down much :-(