Through the introduction of BioDialectics, a conceptual approach intended to extend the ethical considerations of sustainable design, this book analyses how the field engages with and adapts ideas from environmental ethics. Sustainable design is often presented as a response to environmental crises from a socio-technical perspective, while its ethical foundations remain relatively underexamined. To address this issue, the book systematically examines sustainable design ethics through two broad orientations: anthropocentric and biocentric approaches. Rather than treating these perspectives as mutually exclusive, BioDialectics moves beyond traditional biocentrism’s emphasis on the intrinsic value of all living beings by incorporating relational and systemic understandings of human–nature relations. By taking into account historical, geopolitical, and structural factors that shape these relations, BioDialectics proposes an expanded conception of justice that includes both ecological and social concerns and considers the environmental burdens experienced by ecosystems and communities. Drawing on classical and contemporary philosophical work, as well as examples from sustainable design education and sustainable living initiatives, the book provides a structured analysis and conceptual vocabulary for sustainable design ethics. Each chapter identifies key challenges and possibilities, encouraging reflection on the roles and responsibilities of designers. The book will be of interest to academics, researchers, and practitioners working at the intersection of ethics, environment, and sustainable design.