Have discovered the meaning and value of [interior] landscape (…) paysage intérieur à la Rimbaud Pound Joyce as means of unifying and digesting any kind of experience. Should have got to it 20 yrs ago if I hadn’t the rotten luck to bog down in English lit [ie, bog down with Leavis/Scrutiny]… (McLuhan to Ezra Pound, January 5, 1951, Letters 216)

Between the ages of 35 and 40 (roughly, 1946-1951) McLuhan experienced a second conversion, a decade after his first one.  

His first conversion (formalized at Easter, 1937) brought him into the Catholic Church from his vague Protestant upbringing and represented no fundamental change in his core beliefs in God and traditional values. Like many converts today from Protestant denominations to Orthodoxy or Catholicism, this first conversation reflected his doubtless prayerful view that the Catholic Church best attested what he already strongly believed.  While this had great meaning for McLuhan himself, of course, it was nothing particularly unusual or significant for the world at large.

In contrast, his second conversion (a second conversion to the same place!) was driven by the determination (forced on him, as he often pointed out, by contemporary research in anthropology, psychology, archaeology, classics, linguistics, even evolutionary biology) that there is no such thing as privileged experience and that traditional beliefs and values therefore had to be validated, if at all, on the strange foundation of the relativity of all human experience and culture. This conversion, unlike the first, was of fundamental significance generally.

Since McLuhan’s own core beliefs could not be immunized from this insight into experiential relativity, the effect of it was to dissolve his previous world of lived experience.  It had been based on ‘continuity’¹ which he now saw to be fundamentally broken. Hence identity, too, as the correlate of experience, was necessarily broken and was inexorably exposed at every moment to an unbridgeable gap. As he specified two decades after the event in Take Today (1972):

Managing The Ascent from the Maelstrom today demands awareness that can be achieved only by going Through the Vanishing Point. (13)

Now The Maelstrom was plainly no longer viewed as escapist entertainment (as it was in 1946). In fact, it was now experienced as describing that synchronic (or simultaneous) process of Descent/Ascent through which all human cognition, individual and social, is continually (or diachronically) achieved.² 

Partly through the fact that Leavis and the Scrutiny school assigned the care of traditional values to literary culture and partly through the recognition via Havelock and Innis that societies have maintained their cultures through differing modes of communication (especially orality and literacy, but now also the electric), McLuhan came to describe his second conversion as a turn from an exclusive valorization of print and literary values to the inclusive valorization of all forms of communication and culture, literary or not: 

defenders of book-culture have seldom given any thought to any of the media as art forms, the book least of all. The result is that their “defense” might as well be staged on an abandoned movie lot for all the effect it has on the actual situation. When I wrote The Mechanical Bride some years ago I did not realize that I was attempting a defense of book-culture against the new media. I can now see that I was trying to bring some of the critical awareness fostered by literary training to bear on the new media of sight and sound. My strategy was wrong, because my obsession with literary values blinded me to much that was actually happening for good and ill. What we have to defend today is not the values developed in any particular culture or by any one mode of communication. Modern technology presumes to attempt a total transformation of man and his environment. This calls in turn for an inspection and defense of all human values. And so far as merely human aid goes, the citadel of this defense must be located in analytical awareness of the nature of the creative process involved in human cognition. For it is in this citadel that science and technology have already established themselves… (‘Sight, Sound, and the Fury’, Commonweal, 60:1, April 9, 1954, 7-11, here 10-11; emphases added)

For many years, until I wrote my first book, The Mechanical Bride, I adopted an extremely moralistic approach to all environmental technology. I loathed machinery, I abominated cities, I equated the Industrial Revolution with original sin and mass media with the Fall. In short, I rejected almost every element of modern life in favor of a Rousseauvian utopianism. But gradually I perceived how sterile and useless this attitude was, and I began to realize that the greatest artists of the 20th Century — Yeats, Pound. Joyce, Eliot — had discovered a totally different approach, based on the identity of the processes of cognition and creation. I realized that artistic creation is the playback of ordinary experience — from trash to treasures. I ceased being a moralist and became a student. As someone committed to literature and the traditions of literacy, I began to study the new environment that imperiled literary values, and I soon realized that [it] could not be dismissed by moral outrage or pious indignation. Study showed that a totally new approach was required, both to save what deserved saving in our Western heritage and to help man adopt a new survival strategy. I adapted some of this new approach in The Mechanical Bride by attempting to immerse myself in the advertising media in order to apprehend its impact on man, but even there some of my old literate “point of view” bias crept in. (Playboy Interview. March 1969, pp. 26-27, 45, 55-56, 61, 63, here 63; emphasis added)

Already in early 1951, the year of its publication, McLuhan saw The Mechanical Bride as prelapsarian, as a document reflecting conditions before the fall (as he had come to experience it in Poe’s Maelstrom and Joyce’s “pftjschute of Finnegan”):

Mechanical Bride is something that happened before the Flood. Assumed an audience …. It is a wedding announcement found 1000 years from now in a block of concrete… ³

That is, The Mechanical Bride had been written as if the collapse of the tower of Babel had not occurred, as if an author could assume continuity of language, perspective, reason and values with the audience of readers.  Having undergone his second conversion, McLuhan could now see not only that this assumption could not be made (and was therefore not made by the best of modern art), but also that this assumption stood in the way of genuine communication. From now on he would have to take up the question of the symbolists and Pound and Joyce of how to communicate the process of communication (dual genitive!) as the most important step in communication. (The strikethroughs here are not deletions. They are markers of ineluctable gaps in these nouns.)