Current discourse on sustainable architecture is often too narrowly defined and much of the discourse concentrates on technological questions, especially on energy efficiency. A key assumption unquestioned in this approach is the separation between the natural world and the subject, a one-way mode of causation defining the subject’s instrumental relationship with nature. Under this Cartesian paradigm of subject-object duality all things are knowable and controllable and an object (i.e. nature) is considered primarily in terms of its utility to human beings – through technology humans can control the environment and manage resources in a way that meets humanity’s needs and desires. The Modernist slogan ‘Form follows function’ is now replaced by Form follows energy performance. Cloaked and obfuscated under the current approach in architectural practice are the relational connections to the other. Drawing on the work of Martin Heidegger, Maurice Merleau-Ponty and Tetsuro Watsuji, this chapter elaborates a structure of reversibility and attempts to reconceptualise the interconnectedness and ‘interdependentness’ between body, space and nature in relation to the current sustainability discourse in architecture. It argues that scientific and technological advancements alone are not sufficient for a sustainable future. What is urgently needed is a new paradigm where we become aware of relational bodies.