Chapter 9, The Use of Sewing Cards, part 2

The Boole method is a conveyance which will take you safely to wherever the Great Unknown directs you to go. Some people mistake it for the carpet in the Arabian Nights, which took whoever stepped on it wherever he or she wished to go–which is a quite different thing. The true Boole method depends essentially on making a right use of imaginary hypotheses. The magic carpet depends for its efficacy on making a wrong use of imaginary hypotheses.

People get to very queer places on that carpet. I have been for several excursions on it, so I know. One of the places it can take you to is a town where all the front doors open on to a street very like Regent Street; with the most gorgeous millinery, jewellery, and fruits in shop windows; and all the back doors open to wild country where blue roses, black tulips, and the fattest double carnations of all colours (including green ones) grow wild in the hedges and fields; and where all the pigs have wings. Another place that it can take you to is one where pigs can wallow in all the filth they like without soiling their wings; and moths fly into candles without singeing theirs. The carpet will take you straight to whatever place you wish to go to. It is by no means warranted to take you safely back. The advantage of Boole's method is that it is warranted to bring you safe down somewhere on solid earth,—not always the exact place you started from, but a safe and clean place of some kind—and to deposit you steady on your feet, with a compass in your pocket which will show you a straight way home.