Conceptual art describes a movement that emerged in the mid 1960s, and prized ideas over the formal or visual components of traditional works of art. The artists who became involved in it were often motivated to challenge conventional assumptions about art - concepts such as beauty, quality, and the difference between a document and an artwork. They also questioned the conventional means by which the public consumed art, and how it was processed through an increasingly complex network of galleries, museums and critics - institutions which, they believed, gave their work new meanings which they were sometimes uncomfortable with. To question these conventions, they deconstructed the conventional art object - often by-passing traditional institutions - and presented work in diverse mediums, ranging from maps and diagrams to texts and videos. Never a tightly cohesive movement, Conceptualism was instead an amalgam of various tendencies, most of which lost their impetus in the early 1970s, but it remains one of the most influential developments in recent art.

• In some sense Conceptual art represents an extension of the urge to self-reflection and self-criticism in modernist art. Artists since Manet had been questioning various aspects of their art - its material support, the character of its audience, the institutions which conferred value upon it. Conceptual artists merely pushed this further, abandoning traditional media in the process.
• An important characteristic of most Conceptual artworks is their radical 'dematerialisation.' Artists who pursued this path were often influenced by the simplicity of Minimalism, but wished to do away with the bold and bulky forms of Minimalist sculpture and find an art of the barest essentials, one that need not take any physical form at all.
• Conceptual artists link their work to a tradition of anti-aesthetic artwork whose greatest exponent was probably Marcel Duchamp. Abandoning the traditional notion of the art object as something beautiful, finely crafted, and highly finished, Conceptual artists sought to trouble the category of art itself.
• The analysis of art that was pursued by many Conceptual artists encouraged them to believe that, if the artwork was begun by the artist, it was in some way completed by the audience. This idea later gave impetus to what has been called 'institutional critique,' in which artists turned their attention to the institutional contexts in which art is exhibited, and hence to the social, political, and cultural values of society at large. One famous example of this is Hans Haacke's MoMA Poll (1970), in which he used a poll taken from visitors to MoMA to criticize one of the museum's trustees.

Probably the most important precedent for Conceptual art was the work of Dada artist Marcel Duchamp, who in the early 20th century established the idea of the "readymade" - the found object that is nominated by the artist to be a work of art. He inaugurated the idea in 1913 with Bicycle Wheel (1913), which comprises a single bicycle wheel mounted upside-down, by its fork, on a wooden stool, though the most famous of his readymades is undoubtedly Fountain (1917), which was nothing more than a porcelain urinal, reoriented ninety degrees, placed on a stand and signed "R. Mutt." In the 1950s, long after several of his original readymades had been lost, Duchamp re-fabricated works like Bicycle Wheel and Fountain on behalf of the Sidney Janis Gallery in New York. This helped to encourage a resurgence of interest in his work, which not only led to the emergence of Neo-Dada, but also rekindled a widespread interest in idea-based art throughout the contemporary art world.

One of the first to pursue the notion of idea-based art to its logical conclusion was Joseph Kosuth. One of several artists who pioneered the style in New York in the mid 1960s, Kosuth evolved a highly analytical model premised on the notion that art must continually question its own purpose. Launching his ideas most famously in a three-part essay entitled "Art after Philosophy" (1969), Kosuth argued that it was necessary to abandon traditional media in order to pursue this self-criticism. He questioned the notion that art necessarily needed to be manifested in a visual form - indeed, whether it needed to be manifested in any physical form at all.

Examples of this idea-based phenomenon include Lawrence Weiner's 1968-69 "Declaration of Intent," in which he announced that he was relinquishing the practice of creating physical works of art. He justified this by stating that, "Art that imposes conditions - human or otherwise - on the receiver for its appreciation in my eyes constitutes aesthetic fascism."

Proposals such as this were generally intended to open up the possibilities of art (Conceptual artists did not argue that art should take on particular form or another.) Indeed, they could even be taken as artworks in themselves, though the artists tended to be happier to allow some ambiguity, rather than designating what was and what was not art.

These sorts of proposals were echoed by those of a small collective of artists in the United Kingdom who called themselves Art & Language. Their work throughout the late 1960s took the form of a series of essays which tackled various problems related to the fundamental nature of art, and which they published in their journal Art-Language. One of the founding members of the group, Terry Atkinson, wrote the first editorial statement for the publication, and its opening paragraph contained the following: "Initially what conceptual art seems to be doing is questioning the condition that seems to rigidly govern the form of visual art - that visual art remains visual."

Although all of these developments took place more or less independently of each other, it was clear by 1968 that a movement was coalescing around the idea of Conceptual art. In that year a series of exhibitions were staged in New York by art dealer and curator Seth Siegelaub. And, in 1969, MoMA in New York gathered together a number of artists from the movement for a show entitled "Information."

Conceptual art was conceived as a style without traditional boundaries, and hence it can be difficult to distinguish self-conscious Conceptualism from the various other developments in art of the 1960s. Particularly towards the end of the decade, when several post-Abstract Expressionist styles were popular, any style that did not employ traditional painterly or sculptural media was categorized, seemingly by default, as Conceptual. This included tendencies such as happenings, performance art, installation, body art and earth art. However, the principle that united these developments was the rejection of art as a commodity, and it was thought that if art could be reduced to nothing more than ideas then it could not be bought, sold, traded or bartered for.

Although the model of Conceptual art promoted by Joseph Kosuth and Art & Language has come to be the dominant version of Conceptual art - the version seen as the epitome of the style - others explored avenues that have proven to be more influential. Many artists were drawn to Conceptualism out of a desire to remove any trace of authorship from their work. In particular, Sol LeWitt, who in 1967 published what is often taken to be the manifesto of the movement, "Paragraphs on Conceptual Art," advanced an art in which the idea alone should dictate the form of the work - and the idea need not necessarily be 'authored' by the artist. For instance, in Vito Acconci's Following Piece (1969), the artist undertook to follow a member of the public, selected at random, until they disappeared into a private space and could be followed no more: although the form of documentation the work would employ was decided in advance, the shape Acconci's journey would take was entirely dependent on the decisions taken by the randomly selected individual.

The social dimension of Following Piece was made even more prominent in works by more politically interested members of the Conceptual art movement. Some, such as Hans Haacke, created work which controversially challenged the institutional support structure - museums and galleries - in which art was exhibited and validated. And others who gained more prominence towards the end of the movement, in the mid 1970s, addressed their work to even wider areas, looking at labor relations, urban planning, and attempts to monitor alcoholism and vagrancy.

Despite the iconoclastic energy of the movement in its early days - or perhaps because if it - the movement lost its impetus in the mid 1970s. In part this was because of the introspection of some of the artist's work, its dry intellectualism; but the movement foundered also because of the failure of its more politically committed members to make their work connect with new audiences outside of the traditional middle-class gallery-going public. Fractures began to develop in the movement and it eventually ceded to new groups of post-conceptual artists such as the so-called Pictures generation of Cindy Sherman, Richard Prince, Jack Goldstein and Sherrie Levine.

Nevertheless, the moment of classic Conceptualism has continued to interest many artists, and something of its style and austerity and tactics have returned in some of the art of 1990s. The work of a wide variety of artists, from Tino Seghal to Gabriel Orozco to Rirkrit Tiravanija has all been powerfully influenced by the style, and that of a generation of British artists - the so-called Young British Artists, led by such as Damien Hirst - has also been shaped by it, albeit with the added input of Pop art.

"Ideas alone can be works of art; they are in a chain of development that may eventually find some form. All ideas need not be made physical."
-Sol LeWitt

"People, buying my stuff, can take it wherever they go and can rebuild it if they choose. If they keep it in their heads, that's fine too. They don't have to buy it to have it - they can just have it by knowing it."
- Lawrence Weiner