Sentence:  In the light of this observation, consider Number Agreement in a sentence like:/  (120)      "They" seem to me [<sub>S</sub> — to be "fools"/<small>✽</small>"a fool"]/  Here, the <WSD>Predicate</WSD> Nominal "fools" agrees with the italicised NP "they", in spite of the fact that (as we argued earlier) the two are contained in different Clauses at S-structure. How can this be? Under the NP <small>MOVEMENT</small> analysis of "seem" structures, sentences like (120) pose no problem; if we suppose that "they" originates in the — position as the subordinate Clause Subject, then we can say that the <WSD>Predicate</WSD> Nominal agrees with the "underlying" Subject of its Clause. How does "they" get from its underlying position as subordinate Clause Subject to its superficial position as main Clause Subject? By NP <small>MOVEMENT</small>, of course! 
Meaning of the word marked with <WSD> tags:  The part of the sentence (or clause) which states something about the subject or the object of the sentence.