This article suggests that the principle of object-relatedness, introduced by Vygotsky and expanded by A. N. Leontiev, can be used to conceptualize human subjectivity within a profoundly social view of human development. This is achieved by reformulating the premises of cultural-historical activity theory to include the notion that material production, intersubjective exchanges, and human subjectivity form a unified three-fold dialectical system. Focusing on the constant manifold transitions among components of this system as its "modus vivendi" reveals (a) individual and collective processes as being interrelated and co-evolving levels of activity, and (b) the practical relevance of human subjectivity alongside the human relevance of material practices. Such an expanded view posits human subjectivity on a continuum of regulatory mechanisms of social practice, to which both individual and social processes belong. It is further conceptualized as a form of practical transformative pursuits in the world, and as a lawful and necessary moment of human life endowed with the capacity to generate new activity cycles. The co-evolution of collective motives and personal goals, as well as the practical relevance of theoretical constructions, are used as illustrations. (Contains 12 footnotes.)