Syntax has always been considered as the core of language in Chomskyan generative enterprise, and in turn, grammaticality as the core of syntax. Until the Minimalist Program, particularly in the earlier form of the Principles and Parameters Approach known as the Government and Binding Theory, the conditions governing and determining grammaticality, whether in derivational or representational modes, were those of ‘well-formedness’, imposed on syntactic operations or levels from within; that is, the conditions were not motivated by any external systems and were construed within and by syntax proper. In Government and Binding, the structural description of a linguistic expression involved four levels of representation; such levels were then checked by various independent sub-theories (of principles), e.g. projection principle, binding and bounding, which acted as well-formedness conditions, or filters, on the relevant levels. With the advent of the Minimalist Program and the re-interpretation of grammaticality as ‘convergence’ at the two, and only two, interface levels, grammaticality of linguistic expressions comes to be determined language externally; that is, by cognitive performance systems, external to language, yet internal to mind. This article is an attempt to demonstrate how the re-definition of grammaticality and well-formedness conditions as convergence and legibility conditions respectively turns Minimalism into a functional theory, albeit a generative one.