"In conceptual art the idea or concept is the most important aspect of the work.* When an artist uses a conceptual form of art, it means that all of the planning and decisions are made beforehand and the execution is a perfunctory affair. The idea becomes a machine that makes the art. This kind of art is not theoretical or illustrative of theories; it is intuitive, it is involved with all types of mental processes and it is purposeless. It is usually free from the dependence of the skill of the artist as craftsman. It is the objective of the artist who is concerned with conceptual art to make his work mentally interesting to the spectator, and therefore usually he would want it to become emotionally dry. There is no reason to suppose, however, that the conceptual artist is out to bore the viewer. It is only the expectation of an emotional kick, to which one conditioned to expressionist art is accustomed, that would deter the viewer from perceiving this art.

*In other forms of art the concept may be changed in the process of execution"

Source: Sol Lewitt. 1967. "Paragraphs on Conceptual Art". Artforum, 5 n¤.10 (June 1967): 79-83. Reprinted in Garrels, Gary, ed. 2000. Sol Lewitt: A Retrospective. pp. 369-371. New Haven and London: Yale University Press.