Introduction: Sustainability is humanity’s collective ability to sustain development that meets the needs of the present without compromising the ability of the future generations to meet their own needs. Preceding closely to the World Commission on Environment and Development (WCED) Report of 1987, the General Assembly has adopted the UN Declaration, in 1986 [GA RES. 41/128] and has re-emphasized its importance in the UN Millennium Declaration, 2000. Given this anthropocentric rights basis of sustainability it becomes necessary to understand what this ability and development are with respect to the individual human. Problems of relevance, whose resolution benefits more people in general, are often intractable to the methods of rigorous problem-solving (1). Systemic problems of development score high on relevance, low on being amenable to rigor (1) and are considered wicked in nature (2). Consequently, the concern for sustaining human development is wicked and hence calls for taking a design approach as design is considered good at resolving wicked problems(3). This suggests that the collective ability for sustainability with respect to the individual is design ability i.e. to specify solutions that satisfy requirements arising from having to meet self-determined individual (human) developmental needs. However, literature connecting design, sustainability and human development systemically is found lacking and calls for conducting integrative trans-disciplinary research. Prevention and remedial of consequences of technology to the habitability of earth requires the identification, understanding and control of interactions between humans and between humans and the earth systems. These interactions need to be identified generally and understood systemically in the context of being able to sustain human development. However, despite this need for research in interactions and an integrative framework for informing interventions (4) to prevent or remedy unsustainable situations literature that addresses this need is found inadequate. Research Objective: To develop a descriptive model of interaction to be able to identify and describe interactions and understand interactions at human-scale. To develop a prescriptive framework within which to situate the prevention and remedial of problems related to un sustainability by design and prescribe conditions that ensure coherence of design interventions to principles. Research Method: As is the nature of problems of relevance, the proposed research by nature spans multiple disciplines. Descriptive inquiry into widespread literature spanning conservation, development, systems theory and design is conducted before synthesizing a descriptive model of interaction that situates design cycle as a natural cycle based on interpretation of entropy and Gestalt theory of human perception. A manual discourse analysis of a section of the WCED report is undertaken to inquire into the conceptual system (worldview) behind sustainable development to understand human interactions based on worldview. Addressing the need for choosing alternative goals of development for sustainability, Sen’s capability approach to human development is adopted after critically reviewing literature in this area and synthesizing an appropriate integration of design ability, tools, (cognitive) extension and design capability for human development. Models based on theories spanning design expertise, psychology and systems thinking are reviewed and synthesized into a prescriptive framework and two intervention scenarios based on it. The framework, intervention scenarios and the model are illustrated with evidence from qualitative bibliographic analysis of several cases related to sustaining human development in principle. Results: Sustainability is proposed as a human ability; this human ability is proposed to be design ability to sustain human development. A descriptive model of interaction that situates anthropogenic action as a design cycle is proposed. Based on this model, identifying entities and interactions is demonstrated with examples. It is proposed that humans interact, designing, due to and based on their worldview. Expansion of capabilities as stated in capability approach to lead to human development is ‘extension’ of design ability to design capability mediated by tools. Personal and interpersonal interactions at human scale are described through tool-use categories. A prescriptive framework for sustainability by design that holds human needs as central to interventions for sustainability is proposed. Based on this framework, pro-active and reactive scenarios of design intervention for prevention and remedial of un sustainability are constructed and demonstrated using several cases. Summary: Problems of relevance like sustaining human development are wicked in nature and require knowledge and action mutually informing each other. Addressing the inter-disciplinary nature of the problem requires a design approach as design is known to integrate knowledge from several disciplines to resolve wicked problems. The imperative to be able to sustain human development provides the widest profile of requirements to be met and design is shown to be central to meeting these requirements at the various scales that they surface. Sustainability is defined as humanity’s collective ability to develop meeting needs of the present without compromising the ability of the future generations for meeting their own needs. This collective ability translates to the individual’s design ability to specify solutions that satisfy requirements arising out of having to meet self-determined developmental needs. The process of ‘expansion’ -- of capabilities that free people choose and value – that realizes human development is the process of tools affording the extension of design ability to design capability necessary for progressively satisfying requirements arising out of self-determined needs of increasing complexity. It is proposed that humans interact, designing based on and due to their worldview. Personal and interpersonal interactions at human scale are described through tool-use categories. A prescriptive framework for sustainability by design is developed stating conditions to guide systemic design interventions for preventing and remedying unsustainability within pro-active and reactive scenarios respectively. A descriptive model of interaction is developed to situate and enable understanding of interactions. The framework, scenarios and the model are illustrated using several cases related to sustaining human development.