So far we have given two rules: one, the style appropriate to a message will co-ordinate all the channels; two, the scope of the body acting as a medium is restricted by the demands of the social system to be expressed. SAs this last implies, a third is that strong social control demands strong bodily control. A fourth is that along the dimension from weak to strong pressure the social system seeks progressively to disembody or etherealize the forms of expression; this can be called the purity rule. (Douglas 1996: 76)