Within a Principles and Parameters framework, parameters are hypothesized to constitute highly restrictive options, or points of variation of a theoretically relevant sort between languages, responsible for "certain complexes of properties typical of particular types of languages". In 2001, Hawkins provides a succinct and elegant statement: Principles define the structural architecture of human language. This chapter provides a few L2 acquisition examples to illustrate how the feature-reassembly approach illuminates the nature of the learning problems facing the acquirer of a second language beyond that of a feature-selection approach. It is clear that locating the source of morphological variability in a distinct morphological component of the grammar requires a separationist model of grammar, in which the output of syntactic computation is indirectly mapped via morphological (or phonological) module-specific translation procedures to actual phonological forms. The chapter includes some notion of morphological competence in any attempt to account for variability in second language acquisition.