This paper re-examines the meanings and origins of ‘green’ or ‘sustainable’ architecture, focusing on the discourses of radical ecology, particularly as these emerged in the work of California architect, Sim Van der Ryn. Known as one of the founders in the late 1960s of ecological design practice, Sim Van der Ryn embraced the full range of meanings attached the term, ‘ecology’, which cannot be reduced to ‘science’ in the biological or geo-physical senses. Following various strands of ecological thinking within the California counterculture, Van der Ryn proposed an epistemological break with architectural knowledge as specialized technique or ‘technê’, particularly as architectural modernists had imagined this knowledge as an extension of rational-industrial society.