The phenomenon of timelessness has important connotations beyond its popular meaning. Although philosophical, timelessness is frequently applied to objects: there are various suggestions concerning the properties of a timeless object in literature and popular publications, but there is no apparent unanimity on how to realise these characteristics. The approach to sustainable development has broadened, but the impact of immaterial properties of objects needs to be further explored. This thesis addresses these issues through cross-disciplinary research, which is located in industrial and product design and embraces the subject areas of history of design and art, philosophy, cultural studies, cognitive science and sustainable development. The research question is: what makes some objects retain their significance over time and in a changing human context? Although the analyses of literature presented in this thesis have made it evident that the discourse on sustainability, including system thinking, has an apparent focus on material characteristics, there is nothing implicating opposition to an expanded view comprising immateriality. On the other hand, there are indications that the ambiguity of timelessness and related notions, including how the judgment is formed causes confusion for designers pursuing longevity in objects. The aim for this thesis is hence to address this ambiguity and introduce directions, which would allow designers to consider the immaterial qualities of objects when designing and thereby promote a more profound holistic approach to sustainability and sustainable design. The thesis embarks on a deconstruction of timelessness, resulting in the phenomenon being conceptualised: affective sustainability, and subsequently explored through three applications. These initiate new lines of inquiry and allow for the thesis to conclude the key findings of the research. The study concludes that affective sustainability is considered to be a lived experience. Re-considering sustainability and rethinking time, tradition, aesthetics and perception facilitate comprehension of affectively sustainable objects: a designer has to use intuitive judgements and to reach beyond the personal these have to be balanced by the verbal visualisation of thoughts and the study of un-reflected human behaviour outside laboratory settings.

Cette recherche, menée par un designer-chercheur en immersion dans le monde professionnel, interroge la problématique de la conciliation entre pratique réelle et prise de recul réflexive sur le métier. Dans cette visée, elle est en partie fondée sur une question épistémologique : quelles sont les connaissances spécifiques apportées par la recherche en design ? Quelle est sa place dans les cadres académique et professionnel ? De manière plus individuelle, peut-on aujourd’hui mener une démarche de design-poïétique, qui concilie pratique et discours ? Si oui, quelles sont les modalités de cette dualité, et comment l’intégrer dans le monde professionnel ? Explorer les porosités, les échos et les tensions entre praxis, pensées et implications sociales du design permet de développer une connaissance active, ancrée dans le réel. Envisagés sous l’angle commun de l’expérience, ces axes disciplinaires deviennent complémentaires, dépassant les dualismes qui ont trop souvent cours entre théorie et pratique, entre faits et valeurs, entre sciences et société, entre esthétique et politique. Une pensée du design ne peut pas viser à ériger des vérités, mais plutôt à ancrer la pratique dans une éthique, qui respecte les singularités de chaque individu et de chaque situation. Pour le chercheur, il s’agit de commencer par décrire ces relations entre pratique et réflexion pour ensuite les redéfinir en fonction de ses besoins – et permettre à d’autres de le faire. Le profil du praticien réflexif se double alors de celui de théoricien et de passeur. / This research work, lead by a designer-researcher embedded into the professional field, questions the conciliation between real-life practice and reflective hindsight. On this basis, it partly relies on the epistemological issue: what kind of specific knowledge can design research create? How does it fit into both academic and professional frameworks? In a more personal way, how can one conduct a poietic design approach that combines practice and discourse? How to reconcile it with working reality? Exploring the continuities, echoes or tensions between praxis, theories and social implications linked to design practice is a way to develop a dynamic knowledge, rooted in reality. When looked at with a focus on experience, these disciplinary axes become complementary. They overcome the conservative oppositions between theory and practice, facts and values, sciences and society, aesthetics and politics. A design theory cannot aim at seeking the absolute truth, but rather at anchoring practice in ethics that respects the uniqueness of each individual and situation. For the design researcher, that means starting by describing the relations between practice and thinking, in order to rearrange them according to one’s needs. Then, the reflexive practitioner evolves into a theorist and a broker of ideas.