If a modern observer could tour the cities and villages of ancient Greece, he would be astonished at the multitude of gods and goddesses that the Greeks worshipped. They would include some gods whom he recognized, such as Zeus, the king of the gods, or Athena, whose ruined temple in Athens, the Parthenon, has appeared in countless tourist brochures. But many of them would be unfamiliar. There were woodland nymphs, female spirits of nature who might kidnap mortals whom they fancied. There were river gods who could cause floods if they were.....