1942
Plotinus was surely justifiable in his exegesis in the fifth Ennead when he held as platonic doctrine that the One and the Good are identical, and that this is beyond being and beyond knowledge; Proclus taught the same. But whenever a Christian tried to adopt the same pattern of unity among things, [he or she] could not but regard the unique source of all, God, as Creator, that is, as Being in the plenary sense of the name, the source of being to beings… (Bernard J. Muller-Thym)¹ 

Perhaps at first following his close friend and mentor, Bernie Muller-Thym, McLuhan deployed the term ‘plenary’ over and over again throughout his career. He seems to have meant by it, not ‘full’ or ‘fullness’ in some exclusive ontic sense,² but the ‘fullness’ of the natural and spiritual together, in an inclusive ontological sense. As McLuhan said of the symbolists (cited in full below), they effected “the plenary elucidation of [the] verbal landscape, [the] psychological with [the] metaphysical“. Or as he characterized Joyce: ‘Punning on ‘Dublin’, he constantly invites us to regard his drama as the story of ‘doublends joined’. Irremediably analogical, Joyce’s work moves as naturally on the metaphysical as on the naturalistic plane.”³

Here are examples of his use of the term in chronological order from the early 1940s to the late 1970s:

1944
American critics once alerted to the new movements in English criticism would probably bog down in the rhetorical exegesis of Richards and Empson rather than adapt it, as F.R. Leavis did, as a means in a critical journey to the full act of plenary critical judgment.⁴ 

1944
the arduous stage of the journey (…) remains to be accomplished before winning an overall view, which is plenary critical judgment.⁵

1946
As I have often said to [Cleanth] Brooks, the Southern tradition has intense value to-day.  But the agrarian program was a mistaken strategy because rooted in a failure to see the Southern tradition in its intellectual relevance.  The stand should not have been taken on Dixie land.  But on plenary philology.  That is letters understood as the complete education in thought and feeling which fosters an integral humanitas.  That is Viconian ground.  The only fertile soil in the modern world.⁶

1947
There has been no lack of critics who have proclaimed the uplifting qualities of the movies without having noticed anything whatever of what was going on in them. Mr. Tyler [in Magic and Myth of the Movies, 1947] is right, therefore, to concentrate attention on the complexity and eminent snideness of movie art as preliminary to opening up a plenary critique.⁷

1949
English [studies] took over the former functions of Greek and Latin after these had been narrowed to philology. (…) So that the formal teaching of English began and has continued along the lines which first destroyed classical education. The present volumes [under review, Moholy-Nagy’s Vision in Motion and Giedion’s Mechanization Takes Command] suggest a variety of means whereby English might in large measure resume the plenary functions of the older classical education.⁸

1950
Eliot has always insisted on the technical innovations of Laforgue and Rimbaud as basic for his own development. What these poets effected after Baudelaire was the plenary elucidation of verbal landscape, psychological with Laforgue, metaphysical in Rimbaud. They discovered landscape as the formula of a particular emotion of the mind, greatly extending and sharpening the earlier Romantic use of landscape. [James] Thomson [1700-1748], [William] Collins [1721-1759], and even Wordsworth immersed themselves in actual landscapes in pursuit of emotion. Laforgue and Rimbaud invented erudite urban landscapes to control and release precise and complex emotions. [In this way] the Romantics began with the vague search for new art emotions amidst natural conditions and ended with the discovery and precise control of these emotions in art conditions. (…) But the new emotions and the new techniques or formulas for these emotions are inseparable. That is why Eliot always mentions technique and sensibility together, while his commentators discuss only his sensibility.⁹

1951
The impressionists began with sensation, discovered ‘abstraction’, and achieved, finally, a metaphysical art. The picturesque begins with work like Thomson’s Seasons, in the search for significant art-emotion amid natural scenes and it achieved plenary realization in Rimbaud’s metaphysical landscapes — Les Illuminations. The early Romantics sought aesthetic emotion in natural scenes; the later Romantics confidently evoked art-emotion from art-situations.¹⁰

1951
On the labyrinth of the ear, organ of the Incarnation, Joyce built those metaphysical analogies which enabled him to restore the orchestra of the seven liberal arts to its plenary functions. He is never less than the artist of the word. (…) Joyce was at home in all labyrinths because of his original conquest of the stages of apprehension, of the mind in act.¹¹

1953
Such a thought-world [set out in the biblical Book of Revelation]¹² is entirely congenial to the twentieth century as its art and criticism testify. (…) Return to the plenary scope of patristic exegesis (…) can perhaps be taken as a mark of the profound coherence¹³ of modern culture when viewed at its best levels.¹⁴

1953
[Following Innis] every medium of communication has its peculiar bias or limitation. Each one distorts the plenary functions of human oral expression.¹⁵ Writing extends the spatial range of speech but creates mental passivity. Writing fixes traditions but evokes large armies, roads and empires. Seen, however, as a special art form the alphabet refashioned all human experience. The translation of auditory into visual terms set up an inner life in man which separated him from the external world and, in part, from his own senses, as we know from the study of pre-literate societies. The psychic withdrawal caused by the complex process of literacy presents the individual with a train of maladjustments unknown to pre-literate societies. But the fixation of the processes of thought in writing permits that analysis of thought which brings into existence the structures of science and philosophy. Alphabetic writing is itself a radical re-ordering of experience, as we know by contrast with the pictorial or ideogrammic writing of China, which releases a totally different set of of human possibilities in contrast to the unconscious preferences of alphabetic societies. In this sense, an art form establishes basic human attitudes and becomes the very mode of [all human] experience.¹⁶

1954
Pictographic Chinese culture (…) would seem to stand midway between the extremes of our abstract written tradition and the plenary oral tradition with its stress on speech as gesture and gesture as “phatic communion”. And it is perhaps this medial position between the non-communicating extremes of print and pictorial technology which attracts us today to the Chinese ideogram.¹⁷

1955
TV deals with the visual image as radio with the auditory image. That is, there is immediacy or instantaneity of pick-up, projection, and reception. Joyce was entirely aware of these differences in choosing TV as the basic modality of the collective human drama of Finnegans Wake. As immediate sight plus sound, TV permits a full use of the plenary materials of the human drama, namely speech itself, a “verbivocovisual presentment”.¹⁸

1957
[Hugh Kenner] differs from all other commentators in stressing the total relevance of Joyce’s Roman Catholicism to his art. The stress (…) implies Joyce’s radical use of reason as a spiritual faculty and not as a mere instrument. It is Joyce’s awareness of reason in this plenary sense that determines his attitude to the verbal universe. Like Pound and Eliot, Joyce assumed that verbal art in the electronic age had to assume the responsibility of precision and power equivalent to the physical sciences. His work simply shoulders the burden both of the alchemy of the word and of the alchemy of history in an act of inclusive consciousness.¹⁹

1960
[E.T.] Hall’s concept of “the organizing pattern” concerns the fact that “there is no such thing as ‘experience’ in the abstract, as a mode separate and distinct from culture.” Hall is saying here, in effect, what I formulate as “the medium is the message.” (…) Since speech is itself a master technology, it goes without saying that the Sapir, Whorf, Hall, Trager, Lee axis have long followed this line of study. Not being perhaps particularly familiar with the types of cultural analysis directed by the artists of this century toward human technologies as art forms, the social scientists have been unduly shy of a plenary art approach to technology. (…) The problem for the artists in our time is to say everything at once, and this is the problem in a variety of ways for every kind of person in an electronic age.²⁰

1960
Let us suppose for a moment that a team of present-day testers had been available in the year 1500 to find out whether the new book or reading machines and instructional materials were capable of doing the plenary traditional job of education in the future. Would not this team, even as it would today, ask whether the privately read word could measure up as a means of teaching and learning to the memorized manuscript and its formidable extension in oral exegesis and group disputation?²¹

1962
As the entire globe becomes a single computer or what de Chardin calls a noosphere, the advent of satellite broadcasting makes every one of the more than two hundred and fifty cultures of the globe as immediately present to each other as are the telephone subscribers of a single town. The dialogue between cultures will become as pervasive as back-fence gossiping. But, as information movement  expands in this plenary way, the business and politics and diversions of mankind fuse into a single uninterrupted action.²²

1964
The overwhelming trend of film is toward involvement in the creative and social processes alike. Film is now able to digest any kind of theme and to handle it in the mode of an inclusive awareness. The “phantom city phaked of philim pholk” is acquiring the character of plenary consciousness.²³

1970
With the new means of plenary cultural retrieval, ancient clichés are taking their place as transcendental or archetypal forms. (…) It is the process by which new clichés or new technological probes and environments have the effect of liquidating or scrapping the preceding clichés of cultures and environments created by pre­ceding technologies. The world of archaeology and musicology today is entirely concerned with classifying these rejected frag­ments of obsolete and broken cultures.²⁴  

1970
Just as the plenary retrieval techniques of Gutenberg print created the Puritan ideal of a recovery of a purified and primitive Christianity, so the modern anthropologist, using plenary methods of retrieval, has rejected the traditional humanistic or literary view of the gods in favor of a complete resacralizing of pagan art and ritual. The resacralizing of the ancient clichés of ancient technology by an­thropologists places the literary archetypalist in a very embarrass­ing position. The archetypalist, having come to regard the gods as a neutered or “spayed” bunch of moralized entities, now [is confronted by] the anthropologist, who insists on accepting them as real environmental forces completely beyond literary occurrence or control. The gods as cliché technologies are not susceptible to literary classification.²⁵ 

1972
Plenary Indulgences in the Affluent Society
Parkinson stated his law about the nature of  administrations to the effect that any task, however insignificant, will automatically expand to use all the available time and resources of all the available personnel of any operation whatever.²⁶

1972
Shifting “Grounds” Transform “Figures”.
The complicated question of whether authority rested in the pope or in the laity or in the church in plenary council fluctuated wildly with the conditions of travel and information movement from the beginnings of the church to the present. This fact becomes apparent today when there is no more geography in the world as far as verbal intercommunication is concerned. The telegraph, telephone, radio and teletype have caused the disappearance of physical space and national and cultural boundaries, and have restored the most primal conditions of primitive Christianity. At the same time, this instantaneous character brings down an avalanche of historical, bureaucratic confusion upon the new oral church. The electric technology that abolishes central bureaucracy and organization also retrieves the entire past of the church — oral, written, bureaucratic, and historical. We begin to live a kind of Dantesque vision that merges all pasts and presents.²⁷

Posthumous (from the 1970s)
All the extensions of man, verbal or non-verbal, hardware or software, are essentially metaphoric in structure, and that they are in the plenary sense linguistic (…) A “metaphor” means literally “carrying across” from Greek metapherein and was translated into Latin as “translatio”. In a word, metaphor is a kind of bridging process, a way of getting from one kind of experience to another.²⁸