The roots of collaborative epistemology as related to CSCL can be found in Vygotsky's social learning theory. Of particular importance to CSCL is the theory's notion of internalization, or the idea that knowledge is developed by one's interaction with one's surrounding culture and society. The second key element is what Vygotsky called the Zone of proximal development. This refers to a range of tasks that can be too difficult for a learner to master by themselves but is made possible with the assistance of a more skilled individual or teacher. These ideas feed into a notion central to CSCL: knowledge building is achieved through interaction with others.