Take the 2-minute tour ×
English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. It's 100% free, no registration required.

What is the correct usage of phrase "you don't know what you don't know"? Can it be used in formal conversation/writing?

share|improve this question
add comment

6 Answers

up vote 3 down vote accepted

When expressing frustration or exasperation, we often begin by saying something like, "If I had only known..."

  • If I had known your plane was going to be two hours late, I wouldn't have rushed to the airport.
  • If I had known you were going to get such bad grades on your report card, I wouldn't have let you go to the dance last weekend.
  • Had I known the van was going to overheat, I would have driven the car instead.

Yet, in all these instances, life offers no crystal ball; there's no way of knowing what the future holds, or to be cognizant of something we are unaware of. This is the essence of "You don't know what you don't know," only it's being expressed in a comical way, much like Yogi Berra might have said.

(To those unfamiliar with the Yogi Berra reference, he was a professional baseball player who was reknowned for his wry way of saying things, such as, "It ain't over 'til it's over," and, "You can observe a lot by watching." That said, you couldn't know what you didn't know, but now you know.)

Generally speaking, it would not be a good way to express something in formal writing, unless perhaps you were deliberately injecting humor.

share|improve this answer
1  
Of course, Yogi Berra said "I didn't say a lot of the things that I said". –  Jon Hanna Jan 29 '13 at 10:54
    
Incidentally, I'd add that it can also be used in looking toward the future, in awareness that we lack such a crystal ball: We base our plans on our knowledge, and there'll be times where we know there is a gap in that knowledge, but we're also aware that there may be things we can't possibly foresee, because "we don't know what we don't know". –  Jon Hanna Jan 29 '13 at 10:59
    
@JonHanna: Some risk management techniques urge practitioners to consider the "known unknowns" and the "unknown unknowns". –  J.R. Jan 29 '13 at 13:43
    
+1 Great comment! Just Googled Yogi Berra - absolute gold. Yogi also said that "Half the lies they tell about me aren't true"...! On a serious note "Wisest is she who knows she does not know". –  G.S. Mar 25 '13 at 8:21
add comment

Socrates said 'I know that I know nothing', which seems to cover the sentiment. I'd say his version is worthy of formal writing or conversation.

share|improve this answer
    
@Gnawme - +1 (in spirit) for the edit. –  cornbread ninja 麵包忍者 Feb 25 '12 at 0:51
2  
Socrates' dictum may be wise, but I think there's a world of difference between OP's acknowledgement that the amount of things one doesn't know is indeterminate, and Socrates' assertion that, for him, everything falls into that category. –  FumbleFingers Feb 25 '12 at 2:51
add comment

I wouldn't necessarily go as far as call this a "phrase" per se. For me it's a confusing sentence; ambiguous at least.

Whether you can use it or not depends solely on who your audience is. If you're sure the person you're talking to is bound to understand what you're trying to say, then I don't see any problem with using the phrase.

However, if you're unsure the people you're talking to might get confused by the sentence, then definitely don't use it.

Why would you say such a thing anyway? Are you trying to look professional or intelligent? Then use statements which are neither ambiguous, nor difficult to understand in any other way.

share|improve this answer
    
I have heard it in many verbal discussions but haven't seen it in writing and that is why I was wondering if it is informal only. If so what kind of audience would understand it. –  amit_g Feb 25 '12 at 1:53
    
OP's version probably wouldn't come in for as much stick as Rumsfeld's There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – there are things we do not know we don't know., but in essence I expect OP means Rumsfeld's "unknown unknowns" - by which time most of the audience had given up trying to follow him, and were just sniggering. –  FumbleFingers Feb 25 '12 at 2:05
add comment

I haven't heard or read this expression often enough. But the meaning of 'you don't know what you don't know' is clear to me without being ambiguous. However, I feel it may sound a bit rude to some people and so, I wouldn't want to use it in formal conversations or writing unless I know well the person I am saying it to.

share|improve this answer
    
Whilst I understand that the meaning may be clear to you "without being ambiguous", this doesn't exactly explain what 'you don't know what you don't know' means, which is what the question asked. I'm also not entirely sure what it means; it could be meant in the sense that you are literally unaware of what you don't know, or it could be meant in the sense that if you don't know something, you don't know said thing. (I do now think I was harsh in downvoting, as you did cover the formal usage part, but my vote is locked in) –  Alicia Butteriss Feb 4 '13 at 18:24
add comment

This is similar to "you know what you don't know".

I think this expression is used when someone is making statements as if fact when they are just opposite. For example, someone speaking about Darwinism old school as a fact. The one speaking knows about something about theory without proof. This is "you know what you don't know".

share|improve this answer
1  
How is that similar? –  Jon Hanna Jan 29 '13 at 10:59
add comment

It was explained to me along these lines. Each of us has different (spheres of) knowledge, however:

  1. we all know that we know some things (whatever they may be, e.g. "if I tie my shoelaces this way they usually stay done up");
  2. we all know that we don't know some other things (whatever they may be, e.g. for some of us what are the best brain surgery procedures); and lastly,
  3. there are things that each of us don't know that we don't know (I take this to mean they are completely off each of our radars) — and whatever is in this 'sphere' differs from person to person (along with the other two).
share|improve this answer
    
And what of the phrase "you don't know what you don't know"'s formality? –  Matt Эллен Mar 25 '13 at 12:03
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.