In a essay discussing work by Donald Judd, Robert Smithson writes: "A reversible up and down quality was an important feature of the work which Judd showed in the VIII Sao Paolo Bienale. It is impossible to tell what is hanging from what or what is supporting what. Ups are downs and downs are ups. An uncanny natural materiality inherent in the surface engulfs the basic structure.Both surface and structure exist simultaneously in a suspended condition. What is outside vanishes to meet the inside, what is inside vanishes to meet the outside. The concept of "antimatter" overruns, and fills everything, makes these very definite works verge on the notion of disappearance. The important phenomenon is always the basic lack of substance at the core of the "facts." The more one tries to grasp the surface structure, the more baffling it becomes. The work seems to have no natural equivalent to anything physical, yet all it brings to mind is physicality."

(from 'Donald Judd,'  first published in Philadelphia Institute of Contemporary Art Catalogue, 7 Sculptors, 1965)

 

Hans Haacke:

"the working premise is to think in terms of systems; the production of systems, the interference with and the exposure of existing systems. Such an approach is concerned with the operational structure of organizations, in which the transfer of information, energy and/or material occurs. Systems can be physical, biological, or social; they can be man-made, naturally existing or a combination of any of the above. In all cases verifiable processes are referred to."

(from 'For Real: works 1965-2006)