Eliot’s 1919 essay, ‘Tradition and the Individual Talent‘, originally published in The Egoist, runs like a red thread through McLuhan’s work from beginning to end. Here he is at St Louis University in 1938, in his first year of full-time teaching (where the passage in bold announces his lifetime research goal):

Donne, and the later Shakespeare, on the one hand, and the Romantics on the other, have been read at Cambridge as though they were contemporaries of Mr. Eliot — which of course they are. For the continuing life of the language itself is such as to constitute a medium in which they are all contemporary. It is thus, as Mr. Eliot points out in his celebrated essay on ‘Tradition and the Individual Talent’, that the present is able to alter the “past” as much as the “past” nourishes the present. The “past” must be constantly reconsidered in order that it may be available in the present. And just as insensitivity to poetry marks a person as oblivious to the most exact and significant effects of language, so a lack of concern for the situation of contemporary taste and literary expression, is the mark of a radical defect in approaching letters. (‘The Cambridge English School’, Fleur de Lis, 38:1, 24, emphasis added)

And here he is 40 years later in the last substantial essay published before his death:

As cited (…) in Eliot’s (1919) review [of Pound’s Quia Pauper Amavi (which contains three Cantos) entitled “The Method of Mr. Pound”], “Mr. Pound proceeds by acquiring the entire past,” at which point “the constituents fall into place and the present is revealed”. This is the Pound “vortex”, and also the key to Mr. Eliot’s idea of Tradition: “a feeling that the whole of the literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order. This historical sense, which is a sense of the timeless as well as of the temporal and of the timeless and of the temporal together, is what makes a writer traditional”. (‘Pound, Eliot, and the Rhetoric of The Waste Land’, 1979, citing ‘Tradition and the Individual Talent’, Selected Essays, 1932, 14.)

A set of isomorphic problems is posed: what is the nature of time such that there can be “the timeless as well as (…) the temporal and (…) the timeless and of the temporal together”? What is the nature of language such that it is always constituted as “contemporary taste and (…) expression” while yet it “has a simultaneous existence and composes a simultaneous order”? What is the nature of human individuality such that a person can be a particular self, even while constantly changing — and such that that self is at once  differentiated from all others while ‘at the same time’ belonging with others to family, society and tradition? ¹

Aside from frequent direct and indirect allusions to Eliot’s essay, McLuhan’s discussions of it include the following:

The New England ethos naturally finds its highest level of expression in the scholastic man, and the result is that the New England professor is autocratic. There is no social life co-extensive with him, nor one able to embody (…) his thought and actions. Brought up amidst this social nudity (…) T. S. Eliot confronted the situation directly in ‘Tradition and the Individual Talent’. Here it was that he exploded the heresy of “self-expression,” of “message”, and of artistic isolation and futility, which had found such congenial soil in New England. (Edgar Poe’s Tradition, 1944)²

The whole problem for the critic to determine in poetic judgment has been precisely indicated by Mr. Eliot in ‘Tradition and the Individual Talent’: “For it is not the ‘greatness’, the intensity of the emotions, the components, but the intensity of the artistic process, the pressure, so to speak, under which the fusion takes place, that counts.” (Poetic and Rhetorical Exegesis, 1944)

To the merely rationalist and revolutionary mind of the social “planner” or engineer there is never any way of grasping the nature of politics or of art. Rilke makes the same point as Eliot in ‘Tradition and the Individual Talent’: (…) only the traditionalist can be radical. He isn’t content merely to cut the shrubbery into new shapes. The essential impatience and rebellion of the New England mind disqualifies it for political and artistic functions, so that the defection of Henry James and T. S. Eliot was a trauma necessary to the preservation of their talents. (The Southern Quality, 1947)

We welcome the non-Euclidean spaces of modern physics which are not visualizable. And in these fields of relations we find it easy to recognize that any new factor of information or of codification, any new medium or channel, will somewhat modify the entire field of relations.
This admission from the world of mathematics and physics was introduced into literary discussion by T. S. Eliot in 1917 in his ‘Tradition and the Individual Talent’ when he indicated that for the twentieth century it was natural to consider “that the whole of the literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order”. This type of perception, so natural to a world in which all kinds of information flow with electronic velocity, involves the obvious corollary which Mr. Eliot at once pointed out: “The existing monuments form an ideal order among themselves, which is modified by the introduction of the new (the really new) work of art among them. The existing order is complete before the new work arrives; for order to persist after the supervention of novelty, the whole existing order must be, if ever so slightly, altered; and so the relations, proportions, values of each work of art toward the whole are readjusted; and this is conformity between the old and the new.”
To the literary mind, accustomed to the lineal arrangement of language on the page, the notions of simultaneity and of transformation by mutual interaction are very difficult concepts. They are alien and repugnant ideas. But even the literary person has no trouble recognizing the way in which a musical theme or harmony simultaneously modifies all the portions of a musical work. In a musical structure it is easy to observe the total relevance of every phrase to the entire work. The gradual admission of this organic criterion of ‘total relevance’ has come about in all fields of discussion in this century. It is equally the basis of anthropological study of cultures and of critical method in literature. The so-called ‘new criticism’ is, in the main, a recognition of the validity of the ‘total relevance’ attitude to all forms of speech and composition. (Knowledge, Ideas, Information and Communication, 1958)

In an auditory order the speaker becomes a voice in a liturgy, not an orator seeking to alter a point of view. An all-at-once auditory structure makes “self-expression” meaningless. The catalytic concept of T. S. Eliot in ‘Tradition and the Individual Talent’ merely helped us to face the change which had already occurred in our culture in the later nineteenth century. In fact this may well be a principal junction of art: to anticipate change and to invent new models of experience that will enable us to come to terms with change before its full impact can erase earlier achievement. (Romanticism Reviewed, 1960) 

an all-at-once and simultaneous presence of all facets of the past (…) is what T. S. Eliot calls “tradition” in his celebrated essay ‘Tradition and the Individual Talent’. Eliot’s concept seemed quite revolutionary in 1917, but it was in fact a report of an immediate and present reality. Awareness of all-at-once history or tradition goes with a correlative awareness of the present as modifying the entire past. It is this vision that is characteristic of the artistic perception which is necessarily concerned with making and change rather than with any point of view or any static position. (The Emperor’s New Clothes, 1968) 

The mosaic arrangement of multiple items of daily news creates not a picture of the world but an X ray in depth. A picture has a vanishing point related to a fixed position from which the picture is taken, but a mosaic, like a total field of energy or relationships, does not present the means for a point of view or a fixed position. It is an all-at-once or mythical structure in which beginning and middle and end are simultaneously present.
T. S. Eliot explained in his essay ‘Tradition and the Individual Talent’ that all literature and art from Homer to the present constitutes a simultaneous order that is totally modified by the advent of any new work. A new work creates new space for itself and for all the pre-existing space, yet this is quite different from shifting one’s point of view. A point of view depends upon a pictorial space that is uniform and continuous and connected. (Environment As Programmed Happening, 1968)

Bertrand Russell noted of complementarity that the greatest discovery of the twentieth century was the technique of “the suspended judgement” — not single but multiple models of experimental exploration. The need to suspend points of view and private value judgments is indispensable to the programming of total environments.
T. S. Eliot, in ‘Tradition and the Individual Talent’, gave classic statement to the theme of strategy of “the suspended judgment”. Citing the role of platinum as catalyst in effecting new chemical combination, Eliot observed: “The mind of the poet is the shred of platinum. It may partly or exclusively operate upon the experience of the man himself; but, the more perfect the artist, the more completely separate in him will be the man who suffers and the mind which creates; the more perfectly will the mind digest and transmute the passions which are its material.” (Take Today, 97, 1972, citing ‘Tradition and the Individual Talent’, Selected Essays, 1932, 7-8.)

T.S. Eliot has two statements that directly concern our new simultaneous world of “auditory” or “acoustic” space in which electric man now dwells on the “wired planet.” The first passage is from his discussion of ‘Tradition and the Individual Talent’, explaining that “the whole of literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order.” It is the character of auditory space, which we make in the act of hearing, to be a sphere whose center is everywhere and whose margin is nowhere, for we hear from all directions at once.
In the magnetic city of the new electric environment we receive data from all directions simultaneously, and thus we exist in a world sphere of resonant information that is structured and which acts upon us in the auditory pattern. Eliot had regard to the role of the individual talent faced by this new kind of richness of tradition and experience. So it is not strange that our time should witness a revival of many forms of oral culture and group performance, any more than it is strange that we should see on all hands the awakening and cultivation of occult traditions, and new concern with inner life and visionary experience.
For these are resonant things hidden from the eye. The wide interest in every kind of structuralism in language and art and science is direct testimony to the new dominance of the nonvisual values of audile-tactile involvement and group participation. In fact, it could be said that there is very little in the new electric technology to sustain the visual values of civilized detachment and rational analysis.
Mr. Eliot’s second statement on the world of the simultaneous concerns the “auditory imagination”: “What I call “auditory imagination” is the feeling for syllable and rhythm, penetrating far below the conscious levels of thought and feeling, invigorating every word: sinking to the most primitive and forgotten, returning to the origin and bringing something back, seeking the beginning and the end. It works through meanings, certainly, or not without meanings in the ordinary sense, and fuses the old and obliterated, and the trite, the current, and the new and the surprising, the most ancient and the most civilized mentality.”
Eliot here speaks of the mind’s ear, the subliminal depths and reach of the corporate tongue bridging countless generations and cultures in an eternal present. Eliot and Joyce accepted language as the great corporate medium that encodes and environs the countless dramas and transactions of man. Their raids on this vast inarticulate resource have made literary history on a massive scale. (Media Ad-vice: An Introduction, 1973)

My theme for the medievalist of today is that the electronic world has restored the habit of simultaneous awareness which is a primary character of acoustic or synchronic culture. T.S. Eliot’s Four Quartets provides a complete guide to structural or synchronic perception of the world.  He had anticipated this awareness in ‘Tradition and the Individual Talent’: “the historical sense involves a perception, not only of the pastness of the past, but of its presence; the historical sense compels a man to write not merely with his own generation in his bones, but with a feeling that the whole of literature of Europe from Homer and within the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order. This historical sense, which is a sense of the timeless as well as of the temporal and of the timeless and of the temporal together, is what makes a writer traditional.  And it is at the same time what makes a writer most acutely conscious of his place in time, of his contemporaneity.” (The Medieval Environment, 1974) 

Yeats and Lady Gregory sought to regain the modes of corporate awareness of the oral folk as indispensable for the practice of contemporary literature. Eliot had stated his idea of tradition as an acoustic, resonating simultaneity without beginning, middle, or end, when he indicated [in ‘Tradition and the Individual Talent’] the relation of the individual to the corporate life as involving the historical sense, which “compels a man to write not merely with his own generation in his bones, but with a feeling that the whole of the literature of Europe from Homer and within it the whole of the literature of his own country has a simultaneous existence and composes a simultaneous order”. The same simultaneous or acoustic approach to language occurs in his famous definition of “The Auditory Imagination”: “What l call the ‘auditory imagination ‘ is the feeling for syllable and rhythm, penetrating far below the conscious levels of thought and feeling, invigorating every word: sinking to the most primitive and forgotten, returning to the origin and bringing something back, seeking the beginning and the end, It works through meanings, certainly, or not without meanings in the ordinary sense, and fuses the old and obliterated, and the trite, the current,and the new and the surprising, the most ancient and the most civilized mentality. Arnold’s notion of ‘life’, in his account of poetry, does not perhaps go deep enough.” (English Literature as Control Tower in Communication Study, 1974)

It is quite fitting (…) that Alice and Humpty Dumpty should discuss words, since, as the very informing principle of cosmic action, it is language itself that embodies and performs the dance of being. Humpty Dumpty, the cosmic egg, says: “I can explain all the poems that ever were invented — and a good many that haven’t been invented just yet.” This remark by Humpty Dumpty invites a look at the work of T. S. Eliot, whose essay on ‘Tradition and the Individual Talent’ explains that a traditional writer will have the historical sense … “and the historical sense involves a perception, not only of the pastness of the past, but of its presence; the historical sense compels a man to write not merely with his own generation in his bones, but with a feeling that the whole of the literature of Europe from Homer and within it the whole of the literature of his own Country has a simultaneous existence and composes a simultaneous order.” (Empedocles and T. S. Eliot, 1976)