Psychology, quantitative or qualitative, tends to conceive of the human person using metaphysical concepts and to separate the practical, affective, and intellectual aspects of participation in everyday life. Lev S. Vygotsky, however, was working towards a "concrete human psychology," a goal that he expresses in a small, unfinished text of the same name. This book articulates the foundation of and develops such a concrete human psychology according to which all higher psychological functions are relations between persons before being functions, and according to which personality is the ensemble of societal relations with others that a person has lived and experienced. Correlated with concern for the concreteness of human life and the psychology that theorizes it is the idea that to live means to change. However, none of the categories we currently have in psychology are categories of change as such. In this work of concrete human psychology, categories are developed on the basis of Vygotsky's work that are suitable to theorize an ever-changing life, including the language humans use to take control over their conditions and to talk about the conditions in which they live.