What is the Gordian knot?

  According to legendary lore, Gordius, king of Phrygia, tied the neck yoke of his chariot to the pole with a knot so intricate that no one could untie it. An oracle, or tradition of the temple in which it was kept, ran to the effect that whosoever untied the knot should become master of Asia. Young Alexander, afterward called the Great, heard of this knot, and went with his companions to see it. After a careful examination, he drew his sword, it is said, and severed the yoke from the pole. Hence the proverbial expression of solving a difficulty "by cutting the Gordian knot."