ABSTRACT
All fairy stories open, if not explicitly, then implicitly, with the magic formula, " Once upon a time" ...; scientific hypotheses introduce themselves with an "if These are the threshholds of the many mansions of the otherworld. But the child and the half-initiated scientist are not content with the mere starting point and a direction to travel. Most of us unfortunately are children and half-baked scientists, and we want to know not only where the entrances to the otherworld are, but also how far we have to go to take its measure. At certain times the demand is so loud and insistent that nothing will do but to search out an answer. A large part of the history of philosophy is the record of attempts to survey paradise.
