Abstract
Recently, there has been a growing interest, both within theoretical biology and the philosophy of biology, in the possibility and desirability of a theory of development. Among the many issues raised within this debate, the questions of the spatial and temporal boundaries of development have received particular attention. In this article, noting that so far the discussion has mostly centered on the processes of morphogenesis and organogenesis, we argue that an important missing element in the equation, namely the development of language and cognition in general, may play an important role in settling the issue of temporal boundaries. After examining the idea that the development of language, cognition, and action are bona fide biological processes, we explore the consequences for a general theory of development of taking them into consideration