Daniel M. Russell poses what he claims is a deceptively simple brain teaser in his blog:

What short 4-word idiomatic phrase (in English) captures [the] idea of a problem that seems impossible, but actually has a simple and obvious solution?

"Deceptively simple brain teaser" is the best I could come up with, but I don't think it's particularly idiomatic.


So, the originating blogger has posted his intended answer. I would agree that there was no stand-out candidate amongst all the plausible suggestions, so kudos to all those who found a solution.

  • What's wrong with the "Keep It Simple, Stupid (KISS)" suggested in a comment on that blog post?
    – yoozer8
    Commented Mar 1, 2012 at 2:34
  • @Jim: I reckon KISS is advice on how to tackle problems, rather than a phrase that describes a type of problem.
    – Ergwun
    Commented Mar 1, 2012 at 2:37
  • I think you've misunderstood what Russell is saying there - he's posing a "riddle" to which the answer is KISS (Keep it simple, Stupid!), but unless you're already familiar with the answer it's neither simple nor obvious. Commented Mar 1, 2012 at 2:40
  • In fact, probably the appropriate answer here actually is "riddle". Which in certain contexts can mean a superficially complex question where the answer is obvious once you get to it. But I don't think English really has a dedicated word for this sort of thing - if it did, that word would turn up repeatedly in the context of cryptic crossword puzzles, which usually have exactly that characteristic. Commented Mar 1, 2012 at 2:45
  • "Elemental, My Dear Watson", is what came to my mind first, when he said, that the solution is trivial once revealed:)
    – Bidella
    Commented Mar 1, 2012 at 2:46

5 Answers 5


One of the comments on that blog suggests "An egg of Columbus". From the description here, http://en.wikipedia.org/wiki/Egg_of_Columbus, it certainly seems to fit the bill.

  • This is the actual solution. searchresearch1.blogspot.com.au/2012/03/… Commented Mar 4, 2012 at 19:20
  • Except that it's not at all obvious (as in self-evident), nor - given that it requires explanation of the anecdote in order to make any sense - at all simple.
    – Jeremy
    Commented Aug 31, 2016 at 12:13

It's to "cut the Gordian knot."

  • 1
    I like this answer, but I'm not sure it is retrospectively obvious.
    – Ergwun
    Commented Mar 1, 2012 at 4:00
  • 1
    How obvious it is definitely depends on the cultural baggage you carry. Commented Mar 1, 2012 at 4:12

How about

Elementary, my dear Watson

Of course this was never uttered by Holmes in any of Doyle's published works.


I suspect the riddle's answer is quite as likely to be "thinking outside the box, " as it is to be "cutting the Gordian knot".


The Egg of Columbus

"Cutting the Gordian Knot" is to redefine the original problem to make it easy to solve. The Gordian Knot was one which had both ends of the string deeply embedded within the knot so it was near impossible to unravel. Someone (a greek/roman hero IIRC) just cut through it with his sword instead.

  • Welcome to EL&U. Thank you for your contribution, but the Egg of Columbus was already suggested, with a full explanation. Your second suggestion is a good one, but might be strengthened if you could provide a reference or external link. I strongly encourage you to take the site tour and review the help center, as our site is more particular about such things than most discussion forums or Q&A sites are.
    – choster
    Commented Sep 1, 2016 at 2:45

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