I suspect there might be two parses here – one where what is the subject and one where specials is, and that you’ve picked the latter. Note that x3 is underspecified, not singular.
@ebender: Thanks for pointing out the underspecified vs. ‘specified as singular’ distinction, that helps clarify.
You are right that there are two parses (below). As far as I can tell the only difference between them is whether thing(x) or _special_n_1(x) is the first argument to _be_v_id(). So it seems like argument order to the verb is what is defining the subject/object roles.
@arademaker, I get your point that you don’t need the agreement when specials is the object. It makes sense to me that that parse would have the x in thing(x) be underspecified, since the answer could be, e.g. “My specials are wonderful!”
All that said: even though having thing(x) plurality be underspecified is technically right in both cases (since it doesn’t take a position), shouldn’t the parse that has thing(x) as the subject set its variable to be plural instead of underspecified? Or is there some reading where even thing(x) as the subject could be singular?
While the two parses for “what are the specials” may seem hard to distinguish (object vs. subject for “what”), the contrast is clearer in the future tense: “What will the specials be?” vs. “what will be the specials?” A similar but sharper contrast can be seen in “Who will be Elizabeth?” (who will play the part of Elizabeth) vs. “Who will Elizabeth be?” (which part will Elizabeth play).
As for the issue of matching number (plural vs. singular) for the subject and object of the identity copula, it is not right to do this syntactically, since at least in American English there are uses of the identity copula where the two arguments don’t agree in number, as in “The Cowboys are a strong team” and “The strongest team is clearly the Cowboys”. Consider also “Who is the strongest team? … The Cowboys are.”
Hi @Dan, I got your point but I am curious. So in the future the construct is clear marked by the position of the main verb and the auxiliar. But the same question in the present tense would not need to mark the subject/object with the position of the verb too?