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I'd like to ask a question regarding proper grammar in this case.

In a scenario where I say "It is you who doesn't know what you are talking about", is that grammatically correct or should it be "It is you who don't know" in regards to "you" instead?

Thank you for any help in advance.

user135412
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  • This was answered in this question, which was closed as a duplicate of a question that doesn't answer this question. I'm voting to reopen. – Peter Shor Aug 26 '15 at 11:19
  • People say "It is I who am" (classical grammar) and "It is me who is" (new-fangled grammatical innovation looked down upon by pedants). Since you is the same in both the subjective and an objective cases, shouldn't both is and are be considered correct? (Only for singular you, of course.) – Peter Shor Aug 26 '15 at 11:21
  • The frequency of is certainly has increased over the past few decades. See Ngrams. – Peter Shor Aug 26 '15 at 11:26
  • The reason for the doesn't is that the subject of the relative clause is not you (which is in the clause above), but who. And who almost always appears as third person, and therefore for many people is marked as third person and takes doesn't. Note that it's third person singular, not plural (which would be don't, like you), derived from the singular you; but for those people it's still third person. This is the kind of situation that either changes the rule or throws up some frozen idioms that set a new pattern. – John Lawler Aug 26 '15 at 15:48
  • possible duplicate of What rules make “Remember me, who am your friend” grammatical? – Sven Yargs Sep 03 '15 at 01:14

1 Answers1

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It should be:

It is you who don't know

As you correctly say, the pronoun "you" takes the "do" form of the verb. "Does" is the third-person ("he does..."). "You do not know" -> "You don't know" -> "You who don't know".

Jez
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