The paper reviews a limited aspect of the discussion of cleaning of paintings. Statements made in the 1950s by the art historians Ernst Gombrich and René Huygue are examined, and found to be extreme expressions of the humanist culture. Conservation and restoration requires a balance between the scientific and humanist approaches, and the visual and aesthetic aspects of cleaning in particular call for an analysis of empirical observations. The recent analysis of cleaning practices by Gerry Hedley is drawn directly from professional activity. As a contribution to the theoretical basis for restoration it also means a significant step in the development of our profession's autonomy. When principles are confronted with the variables of reality there is no end to the considerations to be made: the paper finally addresses a possible argument in favour of so-called total cleaning .