The relationship between design and architecture questions evidence and organisation by no longer thinking in terms of 'what is and 'what should be'. This is neither linear nor hierarchical, but rather in terms of the practice of 'what could be' and 'how to do it'. By questioning the permanent balance between socially, technically, economically, formally, between the different interlocutors. The work is organised between the architectural firm, the design office, the construction economist, the client, the investor, the policy maker and the user. This is a matter of establishing organisations and values of priorities, know-how, organisational knowledge and distribution between the various players. It is a question of establishing diversity as a major issue, as defined by Edgar Morin, "by linking knowledge" to achieve a rich metropolis. Thinking well about use in a more complex whole. Seizing the real conditions of construction of projects at the scale and identity of a site, of a use. Evaluating the technical means and know-how to be put in place through a process of collective projects between all the people called upon to work on the projects. Remember that architecture must never forget that a building is always greater than the sum of its parts. Its impact must always be the result, as best it can, of a balance between socially embedded in the metropolis, technically thought out and reasoned, economically, ecologically and formally thought out.