New in paperback. Hardcover was published in 2019. This book develops a minimalist approach to cross-linguistic morphosyntactic variation. Ian Roberts argues that the essential insight of the principles-and-parameters approach to variation can be maintained - albeit in a somewhat different guise - in the context of the minimalist programme for linguistic theory. Cross-linguistic variation in word order, null subjects, incorporation, verb-movement, case/alignment, wh-movement, and negation are all analysed in the light of this approach.