The telos of pedagogic action is to make transparent and achievable the principles of evaluation that constitute the practices of the relevant activity. The principles be transparent without being achievable by non-adepts (run 100 m in 11s). Alternatively, they may be achievable without being transparent (as is generally the case in diagnosis). Where the principles of evaluation are transparent and achievable at the outset (eg the criteria for recieving a certificate on a course in computer mediated communication for computer-literate students being that they logon and post five messages during the period of the course), then the relations between transmitter and acquirer are not pedagogic, but rather exchange.