Lewis Carroll, author of Alice’s Adventures in Wonderland, is the pen name of Charles Lutwidge Dodgson, who was an Oxford mathematician and logician. Lewis Carroll’s Pillow Problems (1958), is a collection of 72 challenging, and sometimes amusing, mathematical problems, several of which involve probability. Here is Problem #5. A bag contains one counter, known to be either white or black. A white counter is put in, the bag shaken, and a counter drawn out, which proves to be white. What is now the chance of drawing a white counter?