Dear Reader: I think the main reason I scurried out of my London “flat” late last night, was not so much because I saw a mouse walking just outside my bedroom, but because, instead of flashing by at lightening speed, as in the handful of other times I’ve seen mice in my life (twice in London), this one was leisurely sauntering by, not in any rush to go anywhere. That seemed unnerving… . Never mind, I moved out until the error could be corrected. George Chatfield was right to suggest a few days ago that they should rent cats, or at least cat litter for visitors. The experience didn’t really alter my Popper lecture today at the London School of Economics (“How Experiment Got a Life (of its own)”), except that I omitted some of the slides on transgenic mice. (I will ask the blogsfolk to post the paper here, to be part of a book on philosophy of experiment.)