In the course of the last half-century the interpretation of the first millennium BCE has come to occupy a prominent position not only in the fields of history and the history of religion but, increasingly, also in the humanities and social sciences more generally. One focal point in this development is the growing interest in the idea of the so-called Axial Age. The authors of conceptual historical essays on the Axial Age, Johann P. Arnason and Hans Joas, have somewhat different assessments of the relevance of these references. In all areas where the new openness of thought characteristic of the Axial Age emerged, there were multiple competing conceptualizations and a variety of different schools of thought. Inspired by the evolutionary and cognitive perspective of Merlin Donald, Bellah emphasizes that the Axial Age is expressive of the possibilities that opened up to humankind at the time of the emergence of a fourth evolutionary stage in the development of human culture.

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.