Gordian knot

plural Gordian knots

1. Greekhuman sciencesThe legendary knot tied to a pole near the temple of Zeus in Gordium.
2. broadlyAny intricate and complex problem having a simple solution.

   The knot which you thought a Gordian one, will untie itself before you.

   1785 August 19, Thomas Jefferson, Letter to Peter Carr

   3 more examples

   List his discourse of war, and you shall hear A fearful battle rend'red you in music; Turn him to any cause of policy, The Gordian knot of it he will unloose.

   1599 (date written), William Shakespeare, “The Life of Henry the Fift”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act I, scene i]

   Mr. Tooke thought he had answered this question satisfactorily, and loosened the Gordian knot of grammarians[…]

   1825, William Hazlitt, “The Late Mr. Horne Tooke”, in The Spirit of the Age […] , London: Printed for Henry Colburn, […], →OCLC

   The right hon. gentleman, who was doubtless aware of the popularity of the old English saying, "what is sauce for the goose should be sauce for the gander," shrewdly judged that he could not go far wrong if he cut the Gordian knot in which the publican's disagreement was bound, by declaring his conviction that what was good for the Crown and Cushion, in the Strand, was likewise good for the Three Jolly Tinkers, in Brick Lane; and that, to put an end to the vexed question, the shortest way would be to tar them all with the same brush.

   1881, James Greenwood, chapter 10, in Low-Life Deeps