A type of art in which the idea or ideas that a work represents are considered its essential component and the finished ‘product’, if it exists at all, is regarded primarily as a form of documentation rather than as an artefact. Its origins go back to Marcel Duchamp, but it was not until the later 1960s that Conceptual art became a recognizable movement and acquired its name. It flourished most vigorously in the early 1970s, becoming an international phenomenon and often overlapping with other art forms and movements that were fashionable at this time, notably Arte Povera, Body art, Land art, and Performance art. These have all been seen as aspects of the reaction against the formalism and commercialism of Minimal art. However, Conceptual art has proved just as susceptible to commercial exploitation as other forms of avant-garde expression, with dealers selling the documentation of Conceptual works to collectors and museums. Such documentation takes varied forms, including photographs, sound and video cassettes, texts, maps, diagrams, and sets of instructions, but some Conceptual works do not have any physicality at all, an example being Telepathic Piece (1969) by the American artist Robert Barry (b 1936), consisting of a statement that ‘during the exhibition I will try to communicate telepathically a work of art, the nature of which is a series of thoughts that are not applicable to language or image’. Although some Conceptual art purports to deal with serious political issues, much of it is concerned with deliberately abstruse analysis of language or with the kind of eccentric private concerns shown by Barry. Exponents and admirers of Conceptual art see such activities as posing questions about the nature of art and provocatively expanding its boundaries. Robert Morris, for example, wrote in 1970 that ‘The detatchment of art's energy from the craft of tedious object production…refocuses art as an energy driving to change perception.’ To many people, however, Conceptual art is as pointless as it is pretentious: in 1972 Keith Vaughan wrote that ‘the term is a contradiction in itself, art being the realization of concepts, not just having them’. The initial wave of enthusiasm for Conceptual art was over by the mid-1970s, but there was a substantial revival of interest in it in the mid-1980s (for example in the work of some of the exponents of Neo-Geo). The term ‘Neo-Conceptual’ is sometimes applied to this revival. More recently (especially in popular and journalistic usage) the term ‘Conceptual art’ has often been applied loosely to virtually any avant-garde art that cannot be placed in traditional categories.