Chapter 6 draws the conclusions of the historical review conducted in the previous chapters and critically reconsiders the notion of parameter, reevaluating both its role in Generative Grammar and its theoretical status. First, concerning Linearization parameters like the ones responsible for overt vs. covert wh-movement and head directionality, it is argued that linguistic variation can be attributed to PF-interface conditions having a disambiguating effect on a specific set of syntactic representations which cannot meet bare output conditions. Second, considering Roberts’s (2019) reformulation of argument-drop, verb movement, and V2 as instances of head movement, it is argued that Chomsky’s (2021a) extra-syntactic account of head movement suggests the possibility of developing a unified theory overcoming the duality between the ‘syntactic parameters’ accounting for the emergence of null arguments and verb movement on one side and Linearization parameters on the other. Lastly, the possibility that variation can arise in the narrow syntax is also considered, followed by some final remarks on the latest views on parametric variation in connection with current minimalist assumptions.

Chapter 4 aims at evaluating the classical parameters of GB Theory from today’s point of view. The first parameters discussed are those concerning S′-deletion, Subjacency, long distance anaphora, the Projection Principle, and nominative Case assignment, which are shown either to refer to obsolete theoretical concepts or to be reducible to other, more basic theories. Then, the discussion turns to those parameters whose epistemological status is still being upheld in Minimalism, that is, those concerning null subject, V-to-T and V-to-C movement, polysynthesis, and overt vs. covert wh-movement, by looking at their respective minimalist reformulations. What emerges from this investigation is that, strikingly, the only traditional parameters here reviewed which still enjoy an independent theoretical status are those which in Chapter 2 have been labeled as Spellout parameters. Moreover, the overt vs. covert wh-movement parameter could well be an exception in this sense. In fact, assuming Richards N. (2010) or an equivalent PF-based account is on the right track, wh-movement pertains to the A-P interface.