Note, that the hierarchical definition of activity emphasizes the collective, socially distributed nature of
work, which itself implies division of labor. In addition to the hierarchical structure of activity, activity
theory has a number of other principles:
Object-Orientedness – which states that activities occur in objective, socially and culturally
shaped reality, and therefore have objective properties.
Process of Internalization/Externalization – which states that there is constant transformation and
feedback between internal (mental) and external (physical) activities and one cannot be
understood without another.
Tool Mediation – which emphasizes the social and developmental aspect of labor. Tools shape
the way human agents interact with external reality, and, hence shape external activities. The
constant feedback between external and internal activities, however, causes the transformation of
internal activities as well. Hence, over time tool mediation leads to both cognitive and social
development and learning. Tools become carriers of historically accumulated collective
knowledge embedded in their structure and rules of use.
Development – which states activity and activity systems can only be studied from the
perspective of continuous historical development and evolution