Contemporary art, as any irritable critic will tell you, is the sort of thing that a child could do. Put more temperately, contemporary art lacks proper exclusionary criteria, and this openness often provides little to distinguish between what is art and what is not. Within this by-now-familiar truism is a worthy question, however: if contemporary artworks can be nothing more than an artist's declaration of authorship, or the result of some ephemeral action, how are they understood as art? It certainly doesn't help that the art of the last four decades takes this tension to heart, consistently contending with, and complicating, the very parameters of art.

As Martha Buskirk points out in her erudite study, The Contingent Object of Contemporary Art, the category of the art object has "expanded exponentially" throughout the last century. Contemporary art is thus a particular challenge, as it is often deliberately constituted by things "not immediately identifiable as art": a chunk of fat on a chair, some words printed on the wall, the process of going on a diet, the action of surreptitiously following a complete stranger. "The daunting situation faced by the artist of the early 21st century," Buskirk writes, "is one in which all choices seem possible." Buskirk's book is an expansive inquiry into this thick horizon of potentialities.

An associate professor of art history and criticism at Montserrat College of Art in Beverly, Mass. (and former managing editor of October magazine), Buskirk is well equipped to survey the complex notions that shape the more dematerialized forms of contemporary art. Traversing varied ground with remarkable efficacy, The Contingent Object of Contemporary Art engages a contentious field often approached with intellectual incoherence. With notable argumentative clarity and welcome skepticism, Buskirk examines questions of authorship, originality and the notably ephemeral object through specific examples, ranging from Marcel Duchamp and Robert Rauschenberg to Janine Antoni and Gabriel Orozco. In its wider context, the book also delineates the critical, cultural and legal issues informing the esthetic problems of contemporary art.

Buskirk focuses in particular on concrete examples of the ways that things become works of art, rather than on an attempt to develop objective criteria that might determine exactly what can and cannot be art. This constant deferral of any definition is part of the very contingency that gives the book its title. In this, Buskirk undermines -- as does much of the art she talks about -- the border between art and the "ordinary," choosing instead to examine closely the transposition of things and actions into the frame of contemporary art. As a result, she provides the reader with a rich vocabulary of materials and concepts, as well as tracing the complex details of contemporary artistic practice and its corresponding critical discourse. Among all of these factors, issues of authorship and documentation are brought to the fore.

Although contemporary artists maintain playfulness toward authorship -- including direct disavowal -- the question is still central to contemporary art. According to Buskirk, authorship becomes increasingly important when the ephemeral is itself a medium; the claim to authorship is often the only means of differentiating between art and non-art, as in the prototypical case of the Marcel Duchamp readymade. Furthermore, the complex layering of pastiche, copying and appropriation in contemporary art -- the work of Sherrie Levine, for instance -- makes authorship central, since it "isolates, frames, and provides the context within which the copy or even the found object can be designated an honorary original."

And indeed, Buskirk focuses on works of art that have an odd relation to the world in any conventional sense -- works that exist merely as a certificate of ownership or as series of plans, without a specific original or an actual temporal physicality. Sculptures by Donald Judd, Bruce Nauman or even Wolfgang Laib have this kind of liminal existence, even as they have achieved canonical status. To contend with this problem is to begin to understand the importance of what the art critic Lucy Lippard referred to as "dematerialization," surely a dominant principle in post-Conceptual art.

As works of art became less tangible, and less obviously "art," the rest of the art world hastened to keep up. While Buskirk's demonstrative emphasis is on how the "contingent" has been adopted as an artistic method, she does not fail to highlight an institutional concern over the repudiating of fine art conventions. Buskirk's inquiry thoughtfully extends to the anxiety of collectors and curators -- with their agreement slips, contracts and promissory notes -- rushing to legally control works of art that supposedly do not really exist (such is the case with Sol LeWitt's wall drawings, in which the actual "art" is a page of instructions). Buskirk gives examples of the conflicts over the right to fabricate works by Judd and Dan Flavin, indicating that even the most sophisticated contemporary art collectors, not to mention the artists themselves, have had some trouble acclimating to the character of their contingent production.

Documentation has also served a pivotal role in contemporary art. In some cases, photographs have become the means by which work is known. For example, our familiarity with Robert Smithson's Spiral Jetty comes mainly from documentary sources, rather than direct experience. In many such cases, documentation can be argued to constitute the work itself, as in performance pieces by Vito Acconci, Ana Mendieta, Adrian Piper and other artists. Such work has the effect of blurring the line between event and account, between experience and object. One is often left asking, "What is the work, and what is the document?"

Buskirk has previously written a book on the Richard Serra Tilted Arc imbroglio, and this volume takes a similar, authoritative look at the specific legal disputes that have helped elucidate issues of art and property since the 1970s. Not everyone praises an encompassing relativism as progressive change, and Buskirk only takes into vague account those who maintain an anxious and conservative distance from the proliferation of choices. These are precisely the critics who conflate "contingency" with incoherence, and therefore muddle the field. Still, wouldn't examples of the most adamant contention with its premises help to elucidate the character of contemporary art?

The book is particularly valuable in the way that it disabuses the "everything can be art" generalization. This is accomplished by a deft outlining of the complex set of conditions shaping the contemporary temperament. Here, Buskirk provides much needed, and thought-provoking, critical engagement. Throughout the book, she consistently presents the kind of compelling insight needed to counteract any acerbic conservatism. Moreover, outside of the theorizations and astute analysis of its main arguments, the book also includes some brilliant writing on the work of Antoni, Duchamp, Felix Gonzalez-Torres, Hans Haacke and Warhol. Even if we do not arrive at the end of Buskirk's elegant pages with any clearer indication of what art is, we certainly do so with an inspired sense of what it has become.