The strange objects assembled by the exhibition “L’empreinte” (the imprint, imprinting) compelled me to think creatively, so I silently thanked organizer Georges Didi-Huberman and cocurator Didier Semin for the occasion. But “L’empreinte” often failed to coordinate the materials on view with the concepts elaborated in the accompanying catalogue. From room to room (with nearly 300 items), I thought repeatedly, Why include this object?

Much more coherent than the exhibition is Didi-Huberman’s catalogue essay. It attaches theory to his twentieth-century oddities and provides some history as well to his overarching theme of “resemblance by contact”—from fossils and archeological remains, to the shroud of Turin and death masks, to Auguste Rodin’s casts of body parts and Marcel Duchamp’s Female Fig Leaf, 1950–51. This last serves as an emblem for the entire show, which investigates the direct physical transference of a form or configuration from one surface or material to another, as in molding, casting, and imprinting.

Female Fig Leaf is a curiously shaped cast that Duchamp presented in several different guises, including a photograph in which concavities appear as convexities. This object, or set of objects, materializes ambiguity. Female Fig Leaf might well derive from a cast taken externally from the female sex organ. This consideration would immediately entail some wordplay in French, where moule in the masculine gender means “mold,” while moule in the feminine can, by analogy with its proper referent “mussel,” mean “vulva.” So we are left with something like a mold (un moule) of a “mold” (une moule). The ambiguity of moule hides nothing, yet the object Female Fig Leaf would hide the sex organ, fitting close to it, masklike. Or, as a mold, it could be used to reproduce the sexual form itself. Yet its own form might have been molded from any thin surface or membrane in use as a “fig leaf.” Whatever the case may be, because the female sex organ is a cavity, anything malleable used to fit, cover, and conceal it will assume a convex profile, revealing the form otherwise hidden by its own interiority. The mask—by contact—thus resembles and reveals what it masks. “Resemblance by contact”: this is the principle of the imprint, which might be conceived as the negation of a negation, where the two negatives (the sexual cavity and its convex reversal) never result in a positive. The mold of a cast of a mold becomes yet another reversal, another negative.

I am not reproducing Didi-Huberman’s arguments but writing in something of the same spirit. Is what I’m saying, or what he’s saying, “theory”? Or is it pedantry? Perhaps the matter gets too complicated too quickly. Yet, when it comes to representation, there’s nothing simpler than molding, casting, and imprinting. Twentieth-century artists have been intrigued by the arbitrary order that such mechanistic and mindless techniques of representation create. This may be a way of coming to terms with modernity’s increasingly evasive reality, a way of investigating the crucial difference between reproduction (where the model’s value determines the copy’s) and simulation (where the copy’s value determines the model’s). Too complicated again? Perhaps no such difference can be articulated, however much it may be sensed: to pass from mold to cast to another mold is to experience an intangible difference, but only from within the persistent, transferable sameness of the imprint, a difference-in-sameness as difficult to represent as the inside of a glove or, for that matter, a moule. Molding (with plastics) and casting (with liquids that solidify) are processes easily exchanged; the French uses a single word, moulage. Imprinting by either mold or cast can occur at any time and needs no author (posthumous casting by foundry workers is commonplace in the history of sculpture). Didi-Huberman revels in the anachronism of the imprint, its timely timelessness, which he relates to Walter Benjamin’s notion of history as “constellation,” the chance alignment and perceived congruence of elements of past and present, as if one were the mold and the other the cast, an anonymous relationship that fortuitous events can materialize at any moment.

One of the exhibition’s most provocative images is a sequence of photographs of Jasper Johns taken by Ugo Mulas. The painter is shown rotating his head and pressing it against paper mounted on a wall. In this strained act of imprinting, Johns’ concern was not the head per se, but the body more generally, and especially its envelope, the skin. Johns uses his head mindlessly—not to think but to transfer and imprint a form. The image, Skin, 1964, was hung adjacent to the Mulas photographs that reveal how it came into being. The relationship of Mulas to Johns is symptomatic of the structure of “L’empreinte,” which featured both material imprints and representations of them, often in the form of photographs or elaborate schematic drawings. The first type of object is indexical, whereas the second is an iconic display that takes indexicality as its theme.

In this context, Mulas’ photographs assume a dual identity as both optical projections and contact prints. Their modest presence did not detract from the elegance and economy of Johns’ Skin. But Skin did suffer from its proximity to Giuseppe Penone’s graceless Paupières, 1978, a grandiose graphic recording of the movements of the artist’s eyelids, thirty-three feet wide. By Didi-Huberman’s reckoning, Johns and Penone had something in common: a mere category (“Avec la tête et le visage”) dictated the unfortunate conjunction of these works, hardly a Benjaminian “constellation.”

If Penone constituted a lapse in aesthetic judgment, other entries were category mistakes. Repeatedly, the materiality that “L’empreinte” sought was obscured by instances of imprinting converted to pictorialism. For example, Marcel Broodthaers’ deadpan presentation of five “magic slates” was grouped with a narrative work by Sophie Boursat, who happened to be using “magic slates” herself (these writing tablets eliminate visible inscription with the lifting of their cover, yet retain the imprint invisibly within their base, as if—as in Freud’s celebrated analysis—it were a memory trace). Boursat composed the surfaces of her slates to convey a specific story or allegory, with each slate displaying expressively handwritten words. It would make no sense to operate Boursat’s magic slates, which are stilled like a finished picture, whereas Broodthaers’ remain in a state of material readiness.

Didi-Huberman should know not to confuse material potential with debased modes of pictorialism. His stated interest is the anonymous process of making, which must exclude self-expressive posturing and compositional picturing. How does it feel to make an impersonal imprint? In the catalogue, Didi-Huberman quotes a passage from Gilbert Simondon four times over (I translate it freely): “In order to conceive of imprinting itself, it would be necessary to enter into the mold along with the clay, to become mold and clay at one and the same time, to live through and experience their mutual operation. . . . The clay takes form according to the mold, not the worker.” This commentary, however sensitive, reminds me of a certain public figure’s notoriously base desire to be reincarnated as his lover’s tampon—molded into a moule.

Baseness. It’s as common and material as imprinting. “L’empreinte” takes a stance to rival the base antiaestheticism of “L’informe” (formlessness), the exhibition Yve-Alain Bois and Rosalind Krauss staged last year in the same Centre Pompidou galleries. To some extent Didi-Huberman has emulated Bois and Krauss, but he’s also become critical of their thinking, arguing that their understanding of formlessness is disabled by its own rigidity, which sets the formless in absolute opposition to the formed. Yet Bois and Krauss had chosen many of the same theoretical sources (Georges Bataille, Jacques Lacan, Jacques Derrida) and were already making claims much like Didi-Huberman’s; they took the informe to be an operation and not a reference, a mode of delivery, not the message. Like Didi-Huberman’s critical practice, theirs was designed to resist and deny efficacy to principles of pictorial order, art history’s disciplinary focus. Materiality is an operational base that “L’empreinte” and “L’informe” share. Their curators, would-be antagonists, argue from interchangeable positions, like molds and casts of the same object—working from and working toward—the same object.

Despite a parade of categories and qualifications (spread over 190 pages in the catalogue), Didi-Huberman’s theory of the imprint deals only with the most normative instances; his is imprinting without deviation, distortion, or failure, without degradation or entropy. What happens when the molding material is inadequate to the task of generating recognizable resemblance? Will the imprint slip into the category (or the operation) of formlessness? Not really. “L’empreinte” did include at least one provocative example of deviant imprinting (left unillustrated in the catalogue): on a smooth sheet of cardboard Marie Pierre Thiébaut laid out a grid of his fingerprints (in French, empreintes digitales) using wet clay instead of ink or paint to make the impressions. Such marks thoroughly blur or fail to register the finger’s pattern of papillary ridges, which identify the mark as a functioning fingerprint. Here the imprint is entirely indexical, yet isn’t at all what our culture tells us a fingerprint should look like. This case of lack-of-resemblance by contact should have received more curatorial attention. It broke —it breaks—the mold.

Richard Shiff is Effie Marie Cain Regents Chair in Art and director of the Center for the Study of Modernism at the University of Texas at Austin.