The current exhibition ‘Conceptual Art in Britain 1964-1979’ (until 29 August 2016) at Tate Britain features a sculptural work by Ed Herring titled ‘Proposition’ (1970). It comprises of a filing cabinet and 400 postcards, each one of which was for some time kept by participants and then collected by the artist. Herring said: ‘The whole idea of the activity of the work is involved with the ‘theory of interchange’, known in forensic science, which purports that it is impossible for me to leave or enter a situation without leaving something behind or taking something away. That is the lynchpin of the work.’
You change the situation, the situation in return changes you. And nothing is ever the same.