It used to be simple. A painting of a landscape is a wonderfully literal thing; a straightforward aesthetic object. But what of evaluating nonaesthetic art objects, or contemporary art in general, which has cycled through every possible material and medium in a never-ending hope of creating the New?
It begins and ends with inventing a system to constantly reassess what art is, and why anyone should bother. The theoretical paradigm is continually reinvented to keep up with the production of art objects. Thirty years ago, in "Art and Words," Harold Rosenberg asserts that "A contemporary painting or sculpture is a species of centaur— half art materials, half words (54);" reducing the sentiment further, the only/best way to describe contemporary art is to say that 'art is the discourse about itself.'
Any object produced as art is more or less superfluous to the artistic endeavor, but the artmaking act takes on significance when a suitable explanation can be attached to it, and is successful when "[it] becomes an item of our aesthetic culture, though not necessarily a profound or desirable item (57)." By his reckoning, without the 'invisible content,' art would cease to exist, "though individuals, among them two-year-olds, grandmothers and automobile designers, might continue to satisfy the impulse to make things attractive through form and color (58)." Hence kitsch (and why it's an absolutely necessary foil to 'fine art') and other highly aesthetic popular culture; that's another topic. Suffice it to say that it is an interesting paradigm to consider, but, like many purely abstract theoretical constructions, the reality of undiscussed and spontaneous art objects continuing to be produced and consumed by general audiences refutes the concept— while it would be great (from a theorist's standpoint) to think that the linear progression of painting stopped at Stella, that has naturally not been the case.
Words and theory are certainly essential to serious contemporary art, but as Barbara Rose said some years ago: "Although the logic of minimal art gained critical respect... its reductiveness allowed for a relatively limited art experience." Indeed, many works of the last century are excruciatingly dull to experience in a museum or gallery setting, and (for better or worse) the viewer must come to the object with some commentary in mind, or be faced with interpreting the work from nothing. This is hard work, as the trajectory of art is constantly in motion and, with extremely new work, sometimes all but impossible to track beforehand.
If this is the case, the lay-viewer is a useless part of the cycle of art production and consumption, and the critic is the arbiter of all Truth, the one who passes judgment and who brings an item into the collective aesthetic culture. This surely cannot be the case universally, or art would be dead (really this time). The question then becomes: How does one reconcile the issue of being able to experience works of art in a meaningful way while limiting the need for a tremendous investment in researching all the work you'd like to see before you do so? Moreover, what purpose does the museum or gallery serve if the objects it contains are unnecessary for the art they signify to exist? It seems Rosenberg might argue "you can't" and "there is no purpose" but that doesn't really hold up to, say, the throngs of people who flock to shows who have no idea what they're looking at (whether they care about that is another problem). Museums have recently begun the attempt to give lay-viewers some insight through audio commentaries and long object labels, a worthwhile idea if the commentator has any idea what's going on, but viewers are generally left alone to determine how a work fits into the constantly evolving corpus of current art, or not.
Fortunately, the necessity for detailed explanation of a work is not such an absolute. Rosenberg, writing in 1972, was thinking more about what to do with the Minimalist sculptors and Earthworks artists, and takes a reasonably hard line, however all works must at least be given the chance to exist without critically-applied commentary. In, say, Barbara Kruger's work, the statement made is usually blatant enough to infer from the work itself. In her case especially, the artist takes the matter in hand by using words as part of the physical object. Conversely, something like Matthew Barney's Cremaster cycle is only interesting when the reasoning behind it is explained (well, maybe not even then). In these cases, experiencing Kruger's work in person and reacting to it in an immediate emotional way is just as interesting as talking about it, and the opposite is true of Barney.
The possibility of enjoying an art object in a museum or gallery context is inversely proportional to its reliance on discourse for legitimacy. This is made easier when the work relies on spectacular techniques (Janet Cardiff or Andreas Gursky), horror (Damien Hirst) or whimsy and humor (Sarah Sze or Perry Hoberman). Given that, the discourse about interesting aesthetic objects is still paramount, and is the only thing that makes these works Important Works of Art and not just 'attractive things,' like cars or furniture.
In the end it works out nicely; some art objects are interesting in and of themselves, while others require a little intellectual work to grasp, and still others defy all comprehension or enjoyment. Art is dead; long live art.
Rosenberg, Harold. 1972. "Art and Words," The De-Definition of Art, Collier, pp. 55-68..