I am looking for a less wordy version of the phrase:

'you don't [or can't] know what you don't know'

I would like something suitable for an essay format. Ideally a single word or short phrase that conveys the same concept.

This is a different question to http://english.stackexchange.com/questions/59145/usage-of-the-phrase-you-dont-know-what-you-dont-know which asks about usage without requesting alternatives.


  • 2
    It's hard to answer without knowing the context in which it will be used. But it's already a pretty short and pithy phrase and I think it's extremely unlikely there exists a single word that captures this meaning. Though there is always the "Unknown unknowns" from Donald Rumsfeld: brainyquote.com/quotes/quotes/d/donaldrums148142.html – Marv Mills Oct 2 '15 at 14:16
  • "Be aware of not knowing" ? – Graffito Oct 2 '15 at 14:30
  • I won't post an answer, because we should try to answer the question, not evade it. But isn't "You don't know what you don't know" just about perfect? Simple, one-syllable words saying clearly what's to be said. ...failing that, I think the Rumsfeld quote's as good as you're going to get. – Maverick Oct 2 '15 at 14:36
  • In some similar contexts, you might say that you 'know your own limits'. That's really not a great match for your phrase though, which I agree is quite adequately succinct. – JHCL Oct 2 '15 at 15:46
  • Well, a more polite and less confrontational statement might be: "There is obviously a gap in your knowledge". However, "You don't know what you don't know" amounts to more than that and is, to my way of thinking, an admonishment that the person to whom this is directed is totally unaware of his/her ignorance on a given subject matter that he ought to know about or, more tellingly, is so off the mark in remarks and opinions ventured that no amount of discussion or debate is going to bridge that person's intellectual lacuna. – Peter Point Oct 12 '16 at 13:31

Unknown fits the description. Nothing more is needed.

Or since something can be known about something that is more generally unknown (for example, only its existence might be known), you can go with "unknown unknown", where the first "unknown" is an adjective modifying the second "unknown", which is a noun.

"Unknown unknown" was made famous by Donald Rumsfeld.


I would suggest using You never know as it means you know "something might happen in the future, but you never really know how it will happen or whether or not it will eventually happen." as defined in the link (Macmillan Dictionary).

I understand it might have a different meaning depending on situations you are in, but it seems very close.

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