The concept of knowledge integration remains on precarious ontological and epistemological grounds. Hence, the purpose of this contribution is to suggest a reconceptualization of knowledge integration from the integrationist perspective proposed by the English linguist Roy Harris. In this view, all knowledge is internally generated by the human capacity for sign-making and hence, knowledge arises from creative attempts to integrate the various activities of which human are capable of. Integrationism provides a general basis for knowledge integration, which is further elaborated using ideas from Vygotsky and the notion of activity modalities suggested by Taxén. The result is the activity domain, which can be seen as a core integrating construct for various organizational units like dyads, groups, teams, projects, organizational units, organizations, and entire network of organizations. The activity domain is illustrated by examples from the telecom industry. Implications for a number of organizational issues are discussed, including the Unit of Analysis in organizational discourse, a reconceptualization of the organization, sense-making, communities of practice, and models. In addition, a procedure for analytical and interventional inquiries is suggested. In conclusion it is proposed that a thorough ground for knowledge integration can be established only if human innate predispositions for coordinating and integrating actions are considered. As a consequence, “Knowledge Integration” should be reconceptualized as “Knowledge In Integration” to move the focus from controversies over the nature of “knowledge” to the more prolific concept of “integration”