Heinrich Wölfflin, together with Adolf Hildebrand, William Ivins and Ernst Gombrich, solved a problem for McLuhan in the late 1950s that had been nagging him for most of the decade.  During that time he held (following on Innis, Havelock and Richards) that the introduction of the Greek alphabet, as gigantically reinforced by the advent of printing two millennia later, effected an extreme emphasis on the eye relative to the ear in human experience and communication. Further, he proposed, like Richards if not Innis, that modern devices like the telephone, phonograph and radio were rebalancing that emphasis back towards the ear. At the same time, however, he postulated that photography, comics and advertising were active with such auditory media in revolutionizing visually weighted Gutenbergian experience — but this through the introduction of new visual elements into printed material:

in our own time technology has restored pictorial communication to a public which is completely untrained in pictorial discrimination. (Comics and Culture, 1953) 

I suggest that the real reversal which has overtaken print technology is to be found in the photograph and the movie, and that these forms of total ‘statement without syntax,’ as William Ivins describes it, are utterly unlike telegraph, radio, and TV. Somehow we must unriddle the complex of new messages involved in this new situation which has been created by print technology itself. So far nothing has been done to explicate the situation because we still imagine that these forms of codifying information can co-exist [as atomic units in successive time and space] without transforming one another. This attitude, now suicidal, is yet a natural legacy of print culture. (Printing and Social Change, 1959)

The problem was: how could such increased emphasis on the visual produce (or at least cooperate in producing) a decreased emphasis on the visual?  How could photography, comics, and advertising (augmented by the movies) have a leading role in a pictorial “age of advertising” that yet “somehow” marked “the end of the Gutenberg era” (a phrase McLuhan was already using in the early 1950s¹)? This when “the Gutenberg era” seemed to represented the very acme of visuality?²

The answer that McLuhan discovered late in the 1950s through the art historians was twofold.³  

On the one hand, he found especially in Hildebrand and Wölfflin that tactility characterized all experience. This tactility was not touch in the normal sense but was rather the coordination of the senses — a notion that linked up with McLuhan’s discussions with Bernie Muller-Thym starting already around 1940 concerning the sensus communis in Aristotle and Thomas.

sense of touch is not skin, not direct contact. It is rather the interplay of the senses. (‘Prospect’, 1962)⁴

Hildebrand had shown how tactility was a kind of synesthesia or interplay among the senses, and as such, was the core of the richest art effects. (The Gutenberg Galaxy, 41, full passage given at ‘Heinrich Wölfflin‘)

“Tactility” or interplay among all the senses… (The Gutenberg Galaxy, 81, full passage given at ‘Heinrich Wölfflin‘)

In this understanding, the visual was never absent from experience but its presence was subject to a dynamic emphasis and de-emphasis relative to the other senses as structured by ‘tactility’. As McLuhan could already state in an Explorations article in 1957:

No sense operates in isolation [from the rest of the senses]. Vision is partly structured by ocular and bodily movement; hearing, by visual and kinesthetic experience. (The Effect of the Printed Book on Language in the 16th Century)

Hence McLuhan’s rather strange statements that “the (…) visual (…) is in effect very tactile, resonant, and auditory” and that “Wölfflin taught the Hildebrand stress on visual forms as haptic or tangible-tactile”.⁵

In this way, McLuhan came to understand that the visual could be implicated in opposite effects (like Gutenbergian and post-Gutenbergian experience) for the simple reason that visuality was always implicated in some fashion in all effects. Media were complex structures and visuality was a component in those variable structures like, say, the electron in every atom. The great need, as McLuhan put the point in the ‘Printing and Social Change’ passage above, was to “unriddle the complex of new messages involved in this new situation which has been created by print technology itself”. That is, it was necessary to “unriddle” just what ‘implicated in some fashion‘ amounted to.

On the other hand, he found from the art historians that such “interplay among all the senses”  had to be understood not from experiential input (like the visual appearance of a newspaper or the auditory impression of a symphony) but from experiential output or effect:  

In 1915 Heinrich Wölfflin published his Principles of Art History which has since then revolutionized the study of many matters besides art. His entire approach confirms what I discovered about media: “the effect is the thing that counts, not the sensuous facts“. (Report on Project in Understanding New Media, 1960, full passage given at ‘Heinrich Wölfflin‘)

This meant that “laws of media” had to be formulated (if they were to be formulated at all) from investigative focus on their effects on individual and social experience and not at all on how they happened to present themselves and be sensed.  So, as McLuhan repeatedly illustrated the matter after encountering the work of J.C Carothers in 1959, radio might always be heard by anyone exposed to it, but its effects depended upon the inter-relation between it and the socio-cultural environment into which it was introduced: “the Bedouin with his battery radio on board the camel”, as McLuhan put the point in Understanding Media (16).  And since media were never absent from human history and society, those socio-cultural environments themselves might be investigated as media effects as well. 

The promise was of a new way, or ways, of studying human history and society that would at once avoid problems of relativity (since these, too, could be considered as effects) and supply new ways to address such pressing social and political problems as automation and war.

The upshot of these two points in McLuhan’s own career was that he began to think of media as as future perfect forms subject to their own dynamics. In the 1970s this would lead to the formulation of “laws of media” as an overview of the types of interaction that eventuate between media.  But already in The Gutenberg Galaxy he expressed this insight  as follows:

The relation of tactility to the visual, so necessary to an understanding of the fortunes of the phonetic alphabet, only became starkly defined after Cezanne. Thus Gombrich makes tactility a central theme of Art and Illusion, as does Heinrich Wölfflin in his Principles of Art History. And the reason for this new stress was that in an age of photography the divorce of the visual from the interplay of the other senses was pushed all the way into reaction.  (The Gutenberg Galaxy, 81, full passage given at ‘Heinrich Wölfflin‘)

Much as Harold Innis had pioneered, McLuhan was focusing here on media as a new field of explanation within which “basic laws” (so McLuhan already in 1960)⁶ might be discovered to be at work at work in human psychology and society — or, rather, discovered to have always been at work in human psychology and society. “Reaction” or reversal would be one of such “laws of media” —  one of such laws of media interaction — along with obsolescence, retrieval and  amplification. These were types of effect of media on media through which our “forms of codifying information co-exist [by] transforming one another” (Printing and Social Change, 1959, full passage given above).