The literature on syntactic variation notes several correlations between syntactic variation and morphological variation, suggesting that the two may be causally related. It has been observed, for instance, that placement of the finite verb with respect to clausal adverbs and negation correlates with richness of agreement inflection, where languages with rich agreement tend to place the verb to the left of these elements. And it has been observed that rich inflection correlates with the ability to license null subjects. In a language like Italian, the subject can go unexpressed because the agreement marker is able to reconstruct it.
In either case, however, counterexamples are attested. This could either mean that these correlations are only apparent or that certain ingredients are missing from our understanding of these issues. In this project, we take the second route. Existing generalizations are evaluated and new ones postulated, with the goal of maximizing empirical coverage. In addition, an attempt is made to explain the observable correlations with reference to limitations set by syntactic theory and the language acquisition process.