Realism in theatre is traditionally defined as a mere "seed" of modernism, a simple or crude attempt to copy objective reality on stage. This book challenges this misconception by redefining realism as an under-examined form of visual modernism that positioned theatre at the crux of the unstable interaction between consciousness and the visible world. Tracing a historical continuum of "acts of seeing" occurring on the realist stage, Holzapfel illustrates how theatre participated in modernity's aggressive interrogation of vision's residence in the human body. New findings by scientists and philosophers - such as Diderot, Goethe, Müller, Helmholtz, and Galton - exposed how the visible world is experienced and framed by the unstable relativism of the physiological body rather than the fixed idealism of the mind. The bookillustrates how realist artists across media embraced this paradigm shift, destabilizing the myth of a direct correspondence between reality and representation by giving focus in their art to the subject of the "embodied observer." Drawing from extensive archival research, Holzapfel conducts close readings of iconic dramas and their productions - including Scribe's The Glass of Water, Zola's Thérèse Raquin, Ibsen's A Doll House, Strindberg's The Father, and Hauptmann's Before Sunrise - alongside intensive considerations of artwork by painters and photographers like Chardin, Manet, Nadar, Millais, Rejlander, and Liebermann to show how realist drama was influenced by new approaches towards vision arising in science, visual art, and visual culture. In a radical departure from the dominant critical approach to realism, Holzapfel argues that what realist dramatists sought on stage was not a copy of objective reality but greater acknowledgment of the gap that exists between the eye and the world.