"Conceptual art is not necessarily logical. The logic of a piece or series of pieces is a device that is used at times only to be ruined. Logic may be used to camouflage the real intent of the artist, to lull the viewer into the belief that he understands the work, or to infer a paradoxical situation (such as logic vs illogic).* The ideas need not be complex. Most ideas that are successful are ludicrously simple. Successful ideas generally have the appearance of simplicity because they seem inevitable. In terms of idea the artist is free even to surprise himself. Ideas are discovered by intuition.

*Some ideas are logical in conception and illogical perceptually."

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.