McLuhan’s repeated allusions to the proscenium arch illuminate his views and techniques in interesting ways. The following passages, given in chronological order, will be discussed in subsequent posts:  

The very idea of a single audience looking at a single scene or action through a proscenium arch, so typical of the Renaissance, so unmedieval, is the pure projection of the form of the printed page into drama. (…) By contrast the medieval stress was for cycle plays simultaneously performed as at a circus.  (Explorations 8, 1957)

the medieval stage had been cyclic and simultaneous in presenting many scenes and episodes at once like a three-ring circus. Whereas the new humanist theater developed the proscenium arch with its single perspective such as a single page presents to a reader. Concern for the dramatic unities naturally emerges with the proscenium arch. It is a major difference between the styles of Dante and Milton. (‘Printing and Social Change’, Printing Progress, 1959)

Duccio’s discovery of how to place these figures in an architecturally enclosed space moved toward theatricality and the proscenium-arch space in painting. The sense of the downward thrust of weight generated by perspective strengthens the simulation of a human condition. (Through the Vanishing Point: Space in Poetry and Painting, 1968)

The isolated moment moves us toward photographic stress on visual realism. Darkness is to space what silence is to sound, i.e., the interval. No ambient light — the world of the proscenium arch and stage lighting.  (Through the Vanishing Point: Space in Poetry and Painting, 1968)

Since Sputnik, the planet has become a global theatre under the proscenium arch of man-made satellites. (Culture Is Our Business, 1970)

Since Sputnik put the globe in a “proscenium arch,” and the global village has been transformed into a global theater, the result, quite literally, is the use of public space for “doing one’s thing”. (From Cliche to Archetype, 1970)

When Sputnik went around the planet in 1957 the earth became enclosed in a man-made environment and became thereby an “art” form. The globe became a theatre enclosed in a proscenium arch of satellites. From that time the “audience” or the population of the planet became actors in a new sort of theatre. (‘Roles, Masks and Performances’, New Literary History 2:3 1971)

Since Werner Heisenberg and Linus Pauling, the only remaining material bond is resonance. All physical, psychic, and social processes merge in constant play and replay. There are no more spectators in lab or life, only participants in the Global Electric Theatre. Sputnik created a new proscenium arch that transformed our awareness of planet Polluto — a limited figure against the ground of limitless space. The Apollo age has scrapped Greek Nature as we assume full responsibility for orchestrating our total environment on human scales beyond ideologies. (‘The argument: causality in the electric world’, Technology and Culture, 14:1, 1973)

Today, causing and explaining and predicting merge while teacher-student, consumer-producer, and audience-actor unite in new roles for the Global Electric Theatre [with its proscenium arch of satellites]. The future is not what it used to be… (‘The argument: causality in the electric world’, Technology and Culture, 14:1, 1973)