Аннотация:This chapter outlines the axiomatic bases for developmental science and briefly reviews its historical origins. It sets up the criterion of consistency—if development is conceptualized as a process it has to be investigated as such—rather than relying on standard nondevelopmental outcome "measures" to govern the empirical part of the knowledge construction effort. Development is conceptualized as qualitative transformation of psychological, social, and psychological structures—that emerge and are maintained through person and environment relations. Methodological innovations that are emphasized include: systemic causality, primacy of single-case longitudinal investigations over cross-sectional aggregation of data for large samples, and the focus on qualitative transformation of structures. The chapter also outlines the implications of the Method of Double Stimulation (introduced by Lev Vygotsky) for the study of development. Developmental science is organism-centered—in the human case that entails assuming a person-centered life-course perspective. Contemporary cultural psychology leads to leaving mono-culturally relevant discourses about children far behind and moving towards constructing a general – yet context-sensitive—science of development.