The goal of this collection is to put at the disposal of the linguistic community studies which contribute to a deeper understanding of the nature of language and linguistic variation within the lines that have now been established after fifty years of generative inquiries, often building bridges in the spirit of earlier cognitive traditions, such as the classic work of Plato, the Cartesian view of the mind, and others. While the series will pay particular attention to the traditional tension between descriptive and explanatory adequacy, it will also address many old and new issues, such as the tensions raised at the level of linguistic design through new lines of inquiries often referred to as 'physiological linguistics' or, more dominantly, 'biolinguistics', in particular in the domains of macro- and micro-variations. It is indeed curious that, while the issues at stake are accepted or praised at a rhetorical level, the data that bear on the relevant issues or even the argument at stake are often difficult to access in print, or are often not addressed at all in the form of monographs or dedicated collections. This series will in particular study internal and external factors which bear on the nature of linguistic variation proper, focusing on properties of the Language Faculty and its interface with other domains of the Mind/Brain, as defined within the Minimalist Program, the predominant direction current generative inquiries take and further develop.