Lev Vygotsky proposed that psychology should go beyond immediate experiences; psychology is about processes hidden from direct observation. In Vygotskian cultural-historical psychology scientific activity is understood as study of the world that is based simultaneously on method and methodology. The aim of cultural-historical psychology is to describe directly non-observable psychological structures that underlie manifest behavior. This chapter contains several examples to prove that there is no one-to-one correspondence between the sensory world and reality and even less so between sensory-based and semiotic representations. It discusses one example that follows from application of methodological principles of the cultural-historical approach at the relatively local level of theory-building. Cultural-historical psychology is structural-systemic. Finally, the chapter discusses the two issues at a more local level, that of internalization and that of lexical assumption. Structural-systemic cultural-historical methodology rejects the unidirectional '(cultural) environment-determines-mind' account of the development of mind.

Lev Vygotsky's cultural-historical psychology is a "grand theory" that attempts to provide a unifying approach for the discipline of psychology. This chapter introduces Vygotsky's cultural-historical psychology without oversimplifying the theoretical ideas but at the same time making his sometimes complex ideas accessible. Vygotsky traces the development of various forms of speech from external social speech through to internal private speech to show how humans develop the ability to master themselves, to control and regulate their own mental functions. The significance of Vygotsky's psychological tools is that they provide a bridge between the development of human culture and the cultural development of the human child. According to Vygotsky, the potential concept is a "pre-intellectual formation arising very early in the development of thinking". Vygotsky identified different structures or kinds of generalization that arise during the course of development of concepts.