This paper proposes to account for the asymmetry of wh-movement from a nonsubject versus subject position in root versus embedded clauses from a diachronic perspective. The feature Agree of non-subject wh-interrogatives in root clauses is undergone between an indicative mood feature including an underspecified force feature in M(ood) and a tense verb in terms of obligatory V-2 in OE, but between an interrogative force feature in C and auxiliary do in terms of residual V-2 in PDE. The feature Agree of subject wh-interrogatives in root clauses is satisfied by obligatory V-2 in OE, but it is satisfied by residual V-2 without overt verb movement or do-support in PDE. As for the feature Agree of non-subject whinterrogatives from embedded clauses, there arises no feature conflict between þæt denoting an indicative mood feature including an underspecified force feature and the embedded clause that is specified as the clause type with declarative force feature in OE, and there also arises no feature conflict between that denoting a declarative force feature and the embedded clause that is specified as the clause type with declarative force feature in PDE. As for the feature Agree of subject wh-interrogatives from embedded clauses, it is the same as that of non-subject wh-interrogatives from embedded clauses in OE. By contrast, there arises feature conflict between a declarative force feature in that and an a wh-subject carrying an interrogative force feature from an embedded clause in PDE. This means that a wh-subject which is externally merged in an embedded clause is not compatible with that and resultantly bears out that-trace effect.
2. A non-subject wh-interrogative in root clauses
3. A subject wh-interrogative in root clauses
4. A non-subject wh-interrogative derived from embedded clauses
5. A subject wh-interrogative derived from embedded clauses
6. Concluding Remarks