The social character of psychological phenomena has never been easy to comprehend. Despite the fact that an intricate set of social relations forms our most intimate thoughts, feelings, and actions, we believe that psychology originates inside our body, in genes, hormones, the brain, and free will. Perhaps this asocial view stems from the alienated nature of most societies which makes individual activity appear to be estranged from social relations. One might have thought that the emergence of scientific psychology would have disclosed the social character of activity had overlooked. Unfortunately, a century and a which naive experience half of psychological science has failed to comprehend the elusive social character of psychological phenomena. Psychological science has evi- dently been subjugated by the mystifying ideology of society. This book aims to comprehend the social character of psychological functioning. I argue that psychological functions are quintessentially so- cial in nature and that this social character must be comprehended if psychological knowledge and practice are to advance. The social nature of psychological phenomena consists in the fact that they are constructed by individuals in the process of social interaction, they depend upon properties of social interaction, one of their primary purposes is facili- tating social interaction, and they embody the specific character of his- torically bound social relations. This viewpoint is known as sociohistorical psychology. It was artic- ulated most profoundly and comprehensively by the Russian psycholo- gists Lev Vygotsky and Alexander Luria during, the 1920s and 1930s.