Gordian knot
an intractable problem
Today this word meansA problem that cannot be solved by normal means.
A knot tied by Gordius, king of Phrygia (said to be the father of Midas), with a prophecy attached: whoever untied it would rule Asia.
Alexander, rather than struggle with it, cut it with his sword.
To "cut the Gordian knot" means to erase a problem by changing the rules themselves.