“McLuhan’s Bulbs” argues that the 1960s movement of “light art” is the primary site of negotiation between the discourses of “medium” and “media” in postwar art. In dialogue with the contemporaneous work of Marshall McLuhan, who privileged electric light as the ur-example of media theory, light art eschewed the traditional symbolism of light in Western art, deploying it instead as a cipher for electronic media. By embracing both these new forms of electronic media and also McLuhan’s media theory, light art ultimately becomes a limit term of the Greenbergian notion of medium-specificity, heralding the transformation of “medium” into “media” on both a technological and a theoretical level. This leads to a new understanding of the concept of media as not peripheral, but rather, central to the history and theory of contemporary art. Drawing on extensive archival research to offer the first major history of light art, the project focuses in particular on the work of leading light artist Otto Piene, whose sculptural “light ballets,” “intermedia” environments, and early video projects responded to the increasing technological blurring of media formats by bringing together sound and image, only to insist on the separation between the two. Piene’s position would be superseded by the work of light artists who used electronic transducers to technologically translate between light and other phenomena, particularly sounds. These artists are represented here by Piene’s close friend and colleague, Wen-Ying Tsai. In the spirit of earlier examples of “computer art,” Tsai’s “cybernetic sculptures” used light to announce that art would no longer be defined by its material substrates, anticipating the fluid condition of media that we associate with new media art, and digital technology more broadly, today.