"The artist should know what, and why, things happen in his pictures. Formerly he lived by some kind of mood. He awaited the rising of the moon, twilight, put green shades on his lamps, and this all attuned his mood like a violin. But when asked why his face was crooked, or green, he could not give an exact answer. 'I want it so, i like it like that...' In the end this desire was ascribed to intuitive will. Consequently the intuitive feeling did not speak clearly. And in that case, its condition was not only subconscious, but totally unconscious".

- Kasimir Malevich (1878-1935)

Source: Malevich, Kasimir. From Cubism and Futurism to Suprematism: The New Realism in Painting. Translation by T.Anderson (ed.), K.S. Malevich: Essays on Art 1915-1933, vol. 1, Copenhagen, 1969, pp. 19-21, 23-5, 26-36 and 38-41. Printed in: Harrison & Wood (ed). Art in Theory. 1900-2000. An Anthology Of Changing Ideas. Malden: Blackwell Publishing, pp173-183.

"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.