This chapter reviews a small, selective number of results in the study of the maturation of language, to illustrate its present state. It explores the question about confrontation with biological data, and uses illustrations to provide results. The chapter discusses the possibility of a wedge into the biological study of the human mind, looking at what is possible in the study of the biology of cognition. It reviews the study of language impairment (LI). There is good reason to believe that children with Specific LI are not just the tail of a normal distribution of development. There is a large complex of properties that flows from the analysis of the finiteness system, or generally the unique checking constraint (UCC)-delayed system, as a piece of biological development. Biology takes behavioral genetic data seriously, as part of its enterprise, so the integration of which Salvador Luria wrote has in fact occurred.