This paper advances a theory as to why Vygotsky's research program has remained at the center of international psychological debates, despite its grounding in Marxist philosophy. An important part of the psychological appeal of Vygotsky derives from the fact that he was describing the mental constructs and rule-governed behavior of human development in their account of social, cultural, and historical reality. There have been a number of attempts to create a Marxist psychology during the 1920s and 1930s. These have been less successful because of misunderstandings of Marxism, and indeed of psychology. If Marxism drew on German Hegelian philosophy, British political economy, and French political socialism, then psychology drew on German materialist physiology, British empiricist philosophy, and French Cartesian dualism. Marx attacked the poverty of philosophy and wrote a Critique of political economy, similarly, Vygotsky wrote Educational psychology and attacked the poverty of psychology in his magnum opus, Historical Meaning of the Crisis in Psychology. Vygotsky argued that we must write our poverty of psychology then lay the foundations for a Marxist psychology. That is to create psychology's own capital.