Participatory design originated in Scandinavia in the 1970s and 1980s, motivated by a Marxist commitment to democratically empowering workers and fostering democracy in the workplace. It was avowedly political research aimed to form partnerships with labor unions that would allow workers to determine the shape and scope of new technologies introduced into the workplace.
In early participatory design studies, workers tried to describe computer systems that could automate work while still valuing their craft skills and upholding their autonomy. But because workers had no experience in systems design, they could not begin to speculate on how to build such a system.
What distinguishes participatory design from related approaches such as user-centered design is that the latter supposes only that the research and design work is done on behalf of the users; in participatory design, this work must be done with the users.
Participatory design opposes the notion of a rationalist approach to design, which generally assumes that there is one best way to perform any activity. Theoretically, participatory design is founded on constructivism, a theory that explicitly resists the notion that knowledge can be completely formalized and classified that is to say, tacit knowledge which is implicit rather than explicit, holistic rather than bounded and systematized.
Reference:
Spinuzzi, C. (2005). The Methodology of Participatory Design. Technical Communication, 52(2), 163-174 (12).