Starting from the conceptualization of social participation, as presented in the Processus de production du handicap (Disability Creation Process, PPH) model, this article proposes to analyze an effective form of participation—taking place outside the system envisaged by French public policies—by people with disabilities, in particular, people who hear voices. Beyond scientific debate already well underway—such as the relationship between lay and scientific knowledge, epistemic injustices, or the evaluation of the effectiveness of the work of peers and their contributions to professionals in the mental health, social and medico-social sectors—this article highlights the specific contributions of these peer groups, namely, experiential knowledge and an examination of environmental factors facilitating their emergence. The survey material used was collected as part of an ethnography of the Hearing Voices Movement that began in 2013 and that is ongoing.