Data collected by participant observation in two contrasting types of therapeutic community are compared to reveal broad similarities in the treatment process. In both communities treatment was centrally concerned with reality construction: patients/residents learned to follow, assimilate and reproduce accounts of the community structure and prescriptions for behaviour, and these accounts and prescriptions reflexively constituted the social world of patients/residents. Further, in both communities staff recognised and made deliberate therapeutic use of an aspect of accounts and behavioural prescriptions much reported on in sociological literature, namely their essentially contingent and defeasible character. Thus, alongside processes of reality construction we note processes of reality exploration, whereby patients/residents are encouraged to inspect apparently contradictory prescriptions and accounts within the socially constructed reality of the communities. Staff believed that, in coming to terms with the contingent and defeasible character of accounts and prescriptions within the community, patients/residents would be able to deal with the contingent and defeasible character of social life outside the community less pathogenically.