 Towards a Communication Engineering to Think About the Co-Construction of Public Action? 
This article aims to lay out a scientific approach about the public policies processes of co-construction from the standpoint of communication sciences. To that end, we report the result of an action-research and an ethnographic survey within a French territorial collectivity. This study analyzes a social economy and social innovation policy in order to democratize public policies. This paper argues that communication must be understood not from an inter-understanding perspective but, on the contrary, through an incommunication approach. Consequently, the co-construction processes of public policies are subject to these phenomena of incommunication and require a communicational intervention from a mediator: their role is to build a shared perspective between actors with very peculiar socio-cultural backgrounds.