The idea of activity theory is grounded in social-historical theories and draws heavily on Vygotsky's concept of mediation Engeström expanded Vygotsky's triangle of mediated action and adds three elements to the original triangle. Distinguish the three elements that were incorporated by Engeström to expand the mediated triangle.
1. Community; rules; and division of labour
2. Subject, object and community
3. Object; rules and division of labour
4. Tools of mediators; rules and subject