As described in Eric McLuhan’s introduction to Laws of Media, in the last decade of his life McLuhan became increasingly interested in establishing his work on a scientific basis. There were many reasons for this.

In the first place, the initiation of scientific investigation in any field represents successful communication. Instead of the assertion and counter-assertion that characterize pre-scientific activity, science works on the basis of some accepted framework (Kuhn’s “paradigm”) within which problems may be defined and progress made.  This represents successful communication in two ways.  First, the initiation of science presupposes that the possibility of such focus has been communicated and accepted. Second, on the basis of this founding communication, a new sort of communication becomes possible and this new sort of communication is science.

McLuhan therefore became interested in establishing a science of media as a way of communicating his work and of continuing that work after his death. By the 1970s, he had already suffered a series of strokes. The first of these apparently occurred already in 1960 and was serious enough that the last rites were administered (Coupland 132¹). Then in 1961 his mother died of a stroke. His brain operation in 1967 and a further serious stroke in 1970 produced marked further declines in his health. The handwriting was on the wall and the question of his legacy necessarily imposed itself.

It should not be thought, however, that it was fear of death that motivated McLuhan’s search for a way in which his work might survive him. Instead, McLuhan had a calling and it was in response to that calling that he sought colleagues with a similar calling or, at least, who would work within a new field, or new fields, initiated by it.

His frustration in these efforts may be seen in a letter he wrote to Sheila Watson (26 January 1976,  Letters 516): 

There is no way in which serious work can be promoted without team effort. In isolation, it is ground to powder. My own position here at the University of Toronto is no better than yours at the University of Alberta. Total isolation and futility!

In any case, McLuhan had always wanted to establish some sort of collective research effort. His letter to Harold Innis from March 1951 is typical of this ambition (which McLuhan already entertained by the middle 1940s at the latest):

As Easterbrook may have told you I have been considering an experiment in communication which is to follow the lines of this letter in suggesting means of linking a variety of specialized fields by what may be called a method of esthetic analysis of their common features. This method has been used by my friend Siegfried Giedion in Space, Time and Architecture and in Mechanization Takes Command. What I have been considering is a single mimeographed sheet to be sent out weekly or fortnightly to a few dozen people in different fields, at first illustrating the underlying unities of form which exist where diversity is all that meets the eye. Then it is hoped there will be a feedback of related perception from various readers which will establish a continuous flow. (…) the organizing concept would naturally be “Communication Theory and practice.” A simultaneous focus of current and historic forms. Relevance to be given to selection of areas of study by dominant artistic and scientific modes of the particular period. Arts here used as providing criteria, techniques of observation, and bodies of recorded, achieved, experience. Points of departure but also return. For example the actual techniques of common study today seem to me to be of genuine relevance to anybody who wishes to grasp the best in current poetry and music. And vice versa. There is a real, living unity in our time, as in any other, but it lies submerged under a superficial hubbub of sensation. (Emphasis added throughout.)

Communication — “the actual techniques of common study” — had always been the topic of McLuhan’s concern and the way in which he attempted to initiate investigation of that topic. His confidence in the power of the word motivated him in both senses.  His turn to science in the last 10 or so years of his life simply represented another way in which he attempted to instigate the sort of community which would both illustrate and investigate such communication in action.