When the question word is the subject of the clause, there is no aux verb, eg 'Who saw you?'. I understand this, but why is 'who did see you?' also correct, with respect to Chomsky's linguistic theory (The Minimalist Program) using x-bar theory?

Does the Doubly filled COMP filter play into this? If I've understood correctly, the Doubly filled COMP filter states that the wh-word can only move to the [Spec, CP] if the C is not overt. This makes sense to me in embedded questions, but in direct questions, isn't this a contradiction, as the aux verb moves to the C?

1 Answer 1


First of all, it is not the case that "who" cannot raise over "did" in T (or more precisely - over the tense affix), because it does so when moving from Spec-VP to Spec-TP anyway (under the VP-internal subject hypothesis).

Second, X-bar theory itself says nothing about the constraints on movement; it simply states how the structure is organized - basically that every head has a bar-projection and then there is a specifier and a complement.

Third, Doubly-filled COMP filter uses the conception of COMP present in 70-80's, where both wh-words and complementizers like "that" both were of COMP category, that is C. So it does not really apply to cases where there is a wh-word in Spec/CP and "did" in C.

Now back to the main question - why? Radford in his 2006 textbook "Minimalist Syntax Revisited" suggests that wh-words are attracted by an edge feature [EF] to Spec/CP and tense affix T is attracted to C by a tense feature [TNS], both of features are part of C. He then refers to Pesetsky & Torrego's analysis where wh-subjects can bring [TNS] with them when moving from Spec/TP (unlike wh-objects which never pass that position) and thus satisfy both [EF] and [TNS] of C in Spec/CP. Another option is that wh-subjects never really possess [TNS] and that [TNS] in C simply "needs" to attract something from T or its projections. In wh-object questions [TNS] can only attract whatever is in T and not the subject that is in Spec/TP because Spec position of C is already occupied by the wh-object. In wh-subjects cases, though, both [EF] and [TNS] would be satisfied by just moving a subject to Spec/CP.

I'm not aware of any other analysis of this and honestly I would be very unsatisfied by the one above since it posits the [TNS] feature which has no justification and is mostly unneeded in the analysis of wh-movement in other languages.

  • I have edited the question to add Chomsky's linguistic theory to the part about x-bar trees, as that is what I meant. Are you able to shed light?
    – PolkaDot
    Commented May 30, 2017 at 10:30
  • I'm not sure if I'm following you but like I said X-bar theory simply tells us what structures/trees look like in a formal way and nothing else. You can represent an ungrammatical sentence like "Who did buy pizza?" with an X-bar tree structure but the reason it is ungrammatical has nothing to do with the X-bar formation, so no contradiction is possible here. Commented May 30, 2017 at 12:28
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    It's only ungrammatical if the did isn't stressed. If it is, it's just an ordinary emphatic do. Whether that sits in spec, or whose spec it sits in, is a matter between you and your confessor. I'd say it doesn't invert because it isn't needed; the wh-word marks the clause and is natural to parse as subject, so the inversion marker is unnecessary.
    – jlawler
    Commented May 30, 2017 at 14:01

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