Combining the Latin pro (forward) with thesis (stressed syllable), prosthetics denotes addition or extension. The OED defines "prosthetics" in its plural form as "the branch of surgery concerned with the replacement of defective or absent parts of the body by artificial substitutes." "Prosthetic" derives from the word "prosthesis," which can refer to the addition of a syllable or letter at the beginning of a word, or to surgical prosthesis. The shift from the literal connotation of grammatical prosthesis to the figurative connotation of surgical prosthetics took place in the 16th century, when "prosthesis" was adopted by medical terminology to denote the substitution of an artificial body part for missing limbs or teeth (Jain 32). This article will examine prosthetics in reference to both the actual extension of the body by artificial means, and the virtual extension of the body by various forms of media.

Media theory examines the double meaning of prosthetics, as simultaneously supplementing a deficiency and signaling deficiency in the object to which it is supplied. In Marshall McLuhan's seminal text, Understanding Media: The Extensions of Man, he uses the concept of prosthesis to explain media's function as "any extension of ourselves" (7). Stressing the physicality of media extensions, McLuhan describes the wheel as an extension of the foot, clothing as an extension of the skin, and electric technology as an extension of the central nervous system. Yet as media extends, it also amputates. Although electric technology extends the central nervous system, "such amplification is bearable by the nervous system only through numbness or blocking of perception" (McLuhan 43). Thus McLuhan asserts that a process he terms "autoamputation" accompanies any extension of media.

The concept of amputation has long been associated with theories of prosthesis. By classifying electric technology as a prosthetic extension of the central nervous system, McLuhan combines Marxist theories of industrial alienation with Freudian theories of subconscious extensions. In his theory of the commodity as fetish, Karl Marx's description of the connection between material things and social relations lays the foundation for twentieth century theories of prosthesis: "There is a physical relation between things. But it is different with commodities...There it is a definite social relation between men, that assumes, in their eyes, the fantastic form of a relation between things" (Marx 77). The blurred line between men and the materialism of the commodity sets up a prosthetic system in which social relations are determined by the material relations between commodities, ultimately alienating men from one another and from themselves.

Marx's theory of material social systems was later echoed by Henry Ford, who compared assembly line production to a prosthetic extension of the worker's body. Yet Ford takes a positivist stance, stressing the ability of prosthetics to extend human capabilities. In his autobiography, Ford wrote that technological advances in industrial equipment enabled almost half of his factory workers to exert little physical effort. Many assembly line functions "could be performed by the slightest weakest sort of men [or] satisfactorily filled by older women or children. [Of these] 670 could be filled by legless men, 2,637 by one-legged men, two by armless men, 715 by one-armed men and ten by blind men" (qtd. in Jain 34). Ford explicitly relates machinery to prosthetics, drawing a connection between an assumed deficiency within the amputated human body, and the compensation supplied by man-made machinery.

From a psychological perspective, Freud saw prosthetics as the mediator of several binary relationships including mind/body, internal/external, and conscious/subconscious. Building on the Marxist idea of the mechanical worker, Freud writes: "Motor power places gigantic forces at [man's] disposal, which, like his muscles, he can employ in any direction...Man has, as it were, become a kind of prosthetic God. When he puts on all his auxiliary organs he is truly magnificent; but those organs have not grown on him and they still give him much trouble at times" (Freud 738). The Freudian division between the conscious and subconscious surfaces here, in the notion that the prosthetic extension of man is unmanageable. A split arises between the internal self and external "auxiliary organs", mirroring Freud's distinction between the controlled conscious and unruly subconscious mind. Freud's depiction of the prosthetic God resonates with implications of both physical and psychological amputation and extension, much like McLuhan's electric nervous system.

The ambivalence of Freud and McLuhan towards prosthetics is countered by philosophers, such as Heidegger, who emphasize the amputation of prosthetics and view prosthesis as a form of bodily destruction. Heidegger argues, "the hand is the essential distinction of man...The typewriter tears writing from the essential realm of the hand" (qtd. in Kittler 198). As a mechanical device that regularizes the written word, the typewriter obliterates the handwritten mark, the trace of the body. The prosthetic typewriter mediates between the living hand and the dead typographic word. Even those who avoid using the typewriter constantly come into contact with the typed word. With the destruction of handwriting, communication is amputated in the sense that man's "essential distinction" is no longer present.

Jacques Derrida also examines writing as a prosthetic device, which he terms "the supplement." Yet Derrida approaches the prosthetic supplement, not as Heidegerian amputation, but as a neutral term that "signifies nothing, simply replaces a lack" (Derrida 921). For Derrida the supplement represents not only the act of writing, but also the precarious relationship between terms like 'speech' and 'writing,' which he argues should not be stacked in a hierarchy, but rather viewed as supplementing one another. Derrida explains his position on the relationship between writing and the body when he asserts "that in what one calls the real life of these existences 'of flesh and bone'...there has never been anything but writing; there have never been anything but supplements, substitutive significations which could only come forth in a chain of differential references" (919). Writing determines how we perceive existence, identified by lack as much as by supplementation.

Derrida's student, Bernard Stiegler, built on his teacher's arguments about the supplement, stressing the prosthesis of writing and memory: "What is exceeded is the essential fallibility of a person's memory that, as living, is mortal; the supplement of writing allows that person to confide the trace of his or her intuitions, which become as a result transmissible, to future generations" (Stiegler 245). Within the concept of the supplement, Stiegler compounds living and dead, interior and exterior. His argument returns to the double nature of prosthesis as extension and amputation when he writes, "the supplement, marking the default of origin, does nothing but try and fill this default in; and yet, in doing so, it can only affirm it as necessary..." (260). Like Derrida, Stiegler does not use the supplement as a device for separating the artificial and the real, but rather as a concept that is inseparable from existence, and in which many seeming oppositions collapse together.

Many contemporary artists have taken on the implications of prosthetic media theory in their work. Among the most notable is Cindy Sherman, who uses prosthetic devices in her series of untitled photographs. In Untitled 205, Sherman poses for the camera wearing prosthetic breasts and pregnant stomach. Referencing Raphael's La Fornarina, Sherman alludes to the strategies of 16th century portraiture, while drawing attention to the prosthetic extension of the body. In this photograph, Sherman raises a number of questions. In its obvious allusion to an earlier form of portraiture, does the posed photograph have a prosthetic relationship with the painted image? Is the camera a prosthetic eye, in much the same way that the breasts and stomach are a prosthetic extension of the subject? In a scenario in which so many elements are constructed, where does the body end and prosthesis begin?

Cindy Sherman, Untitled 205, 1989
color photograph, 53 1/2 x 40 1/2 inches

Sherman's photograph also alludes to current debates over the fetishization of prosthesis, and its site as a battleground for issues revolving around gender. The association of prosthetics with castration and/or extension of the phallus is a point at which media theory often takes up issues of gender and sexuality. Rosalind Krauss does this her 1996 article, "Informe" without Conclusion, when she argues against the Lacanian feminization of the wound, and the "fetish-veil of the castrated woman" (98). Using Untitled 205, Krauss illustrates Sherman's emphasis on "the work of gravity, pulling on the prosthetic devices attached to the bodies of the sitters, and thus disaggregating the formal wholes that high art holds together" (95). According to Krauss, the delineation of prosthetic forms within the photograph is a deconstruction of the body and a "strong countercurrent to the constellation form/meaning" (98). Sherman's use of prosthetics not only alludes to extension and amputation, but also to the breakdown of the body through this push-pull relationship.

The charged territory of prosthetics maps both attraction and repulsion, the desire for extension and the fear of amputation. McLuhan's metaphorical central nervous system, electrically amplified, fuses the prosthetic with the body, complicating its status as mediator between binaries of internal/external and living/dead. Some media theorists have argued that prosthetics alter the body to the point that humans become cyborgs. In Donna Haraway's essay, A Cyborg Manifesto, she argues, "Late twentieth century machines have made thoroughly ambiguous the difference between natural and artificial, mind and body, self-developing and externally designed, and many other distinctions used to apply to organisms and machines" (152). Technological advancements in surgical prosthetics push boundaries between the body and prosthetic devices to the point that the (natural) body becomes indistinguishable from the (artificial) prosthetic.

Yet by definition, prosthetics concerns a replacement for that which is missing, an artificial mediator between amputation and extension. In his book Gramophone, Film, Typewriter, Friedrich Kittler writes, "The computer and the brain are functionally compatible, but not in terms of their schematics" (Kittler 249). Like the schematic divide between computer and brain, theories of prosthetics contain distinctions and deconstructions, variably mediated by the charged middle ground of the "artificial substitute."

Sarah Coffey