Vygotsky's Zone of Proximal Development and Krashen's i+1: Incommensurable Constructs; Incommensurable Theories

Second language scholars, in public research and in public discussions,have suggested that Krashen's construct of i + 1 is similar to Vygotsky's zone of proximal development and that it might therefore befeasible to integrate the two constructs in a way that would be productive for second languageacquisition (SLA) research. After surveying publications relevant to the issue, we argue that thisenterprise is futile, not only because the concepts are unrelatable, but also because they arerooted in incommensurable theoretical discourses. We also propose a way in which SLAresearch and theory might deal with incommensurability.