Not surprisingly, several linguistic, learnability-theoretic and acquisitional questions issue from the set-theoretical approach of Wexler and Manzini and from Hyams's developmental approach. Some of these questions are identified, discussed and analysed in the following pages.

An examination of the formal approach

In some important respects the set-theoretical model of Wexler and Manzini appears to be a step in the right direction. Linguistically, the model has given the idea of a multi-valued parameter a concrete shape. It has also raised interesting questions regarding the way parameters could be related to each other, basically as to how independent the fixing of the one parameter is from that of another. However, one should remember that the set-theoretical approach, as it is presented by these authors, is perhaps more of a tour de force than an empirically viable theory; for one thing, it is deterministic in the sense that the environment's role is primarily one-way, i.e. that of providing input, and not backing it up by some form of monitoring of the knowledge acquired in the first instance; moreover, it is far too deterministic to be psychologically convincing and too conservative to be applicable to a wide range of parameters. As a result, it may be necessary to put some empirical flesh on the formal skeleton it furnishes.