"Haacke's systems have a limited life as an art experience, though some are quite durable. He insists that the need for empathy does not make his work function as with older art. Systems exist as on-going independent entities away from the viewer. In the systems hierarchy of control, interaction and autonomy become desirable values. In this respect Haacke's Photo-Electric Viewer Programmed Coordinate System is probably one of the most elegant, responsive environments made to date by an artist... Boundary situations are central to his thinking."
A "sculpture" that physically reacts to its environment is no longer to be regarded as an object. The range of outside factors affecting it, as well as its own radius of action, reach beyond the space it materially occupies. It thus merges with the environment in a relationship that is better understood as a "system" of interdependent processes. These processes evolve without the viewer's empathy. He becomes a witness. A system is not imagined, it is real.
From System Aethetics, Jack Burnham 1968 pg 35