This paper investigates the role of morphology-syntax interactions in
explaining apparent parametric variation in Germanic syntax. It is arg
ued that the Spec, TP parameter (Bures 1993; Bobaljik and Jonas 1996)
is a reflex of aspects of the inflectional morphology that divide the
Germanic languages into two groups, and not simply an arbitrary parame
ter as previously assumed. The theory of distributed morphology is ado
pted and leads to the following position. Complementary distribution b
etween tense and agreement markers in a language must be taken to refl
ect FUSION of the functional heads in that language. This fusion is on
ly possible if head movement in the syntax has concatenated the releva
nt heads in a specific configuration. The required configuration in tu
rn follows from a derivation that precludes the licensing of Spec;TP.
Thus, only languages that do not have this complementarity in their in
flectional morphology may utilize the syntactic derivation that licens
es the specifier of TP.