 Education involves argument and discussion. It is in this sense dialogical. The term ‘argument’ was used by Neurath broadly, to include the case or point being made and communicated, both senses of demonstration. Neurath wrote that to argue requires one to distinguish between essentials and incidentals (Neurath 1945/1973, 239). So a visual argument is ‘a combination of verbal and visual aids leading to the essentials’ (ibid., 240). 