A key passage of "Understanding Media" can be found on page 8 (1994 MIT edition): the content of any medium is always another medium, and the message of the new medium is the change of scale/pace/pattern that it introduces into human affairs. This point of old media becoming the content of new media is reiterated again on McLuhan's chapter on radio (page 305, MIT edition): "The content of the press is literary statement, as the content of the book is speech, and the content of the movie is the novel."
PAGINATION NOTE: the page numbers listed below with "-EM" are from "Essential McLuhan", not directly from Understanding Media. Note that the 1964 Understanding Media edition has different pagination than the widely circulated MIT edition (1994): pages 23-24 of the 1964 edition align with page 8 of the MIT edition, for example. Pagination from the 1964 edition is marked with "-ORIG" below, while 1994 MIT page numbers are indicated with "-MIT".
[149-EM] {media theory, mechanical, body, electric, electricity, senses, nervous system, nerves, global, space, time, planet, technology, media, extension, extend} During the mechanical ages we had extended out bodies in space. Today, after more than a century of electric technology, we have extended our central nervous system itself in a global embrace, abolishing both space and time as far as our planet is concerned.
[149-EM] {} Any extension, whether of skin, hand, or foot, affects the whole psychic and social complex..
[150-EM] {} As electronically contracted, the globe is no more than a village. Electric speed in bringing all social and political functions together in a sudden implosion has heightened human awareness of responsibility to an intense degree.
[15?-EM] {} ...the medium is the message... the personal and social consequences of any medium -- that is, of any extension of ourselves -- result from teh new scale that is introduced into our affairs by each extension of ourselves, or by any new technology..
[23-24-ORIG, 8-MIT, 151-152-EM] {remediation, Bolter, Grusin, sense ratios, light, electricity, medium, message} The electric light is pure information. It is a medium without a message, as it were, unless it is used to spell out some verbal ad or name. This fact, characteristic of all media, means that the "content" of any medium is always another medium. The content of writing is speech, just as the written word is the content of print, and print is the content of the telegraph. If it is asked, 'What is the content of your speech?,' it is necessary to say, 'It is an actual process of thought, which is itself nonverbal.' An abstract painting represents direct manipulation of creative thought processes as they might appear in computer designs. What we are considering here, however, are the psychic and social consequences of the designs or patterns as they amplify or accelerate exsiting processes. For the "message" of any medium or technology is the change of scale or pace or pattern that it introduces into human affairs. The railway did not introduce movement or transportation or wheel or road into human society, but it accelerated and enlarged the scale of previous human functions, creating totally new kinds of cities and new kinds of work or leisure. This happened whether the railway functioned in a tropical or northern environment, and is quite independent of the freight or content of the railway medium."
[154-EM] {} [Paraphrase: There is not "good" or "bad" media: new technology adds itself to what we already are.]
[160-EM] {} Print created individualism and nationalism in the sixteenth century.
[162-EM] {} A hot mediaum is one that extends one single sense in "high definition." High definition is the state of being well filled with data: [A photograph is, visually, "high definition." A cartoon is "low definition," simply because very little visual information is provided.]... Hot media are, therefore, low in participation, and cool media are high in participation or completion by the audience. [DOUBLE CHECK THE TRANSCRIPTION OF THIS CITATION]
[162-EM] {} Intensity or high definition [hot] engenders specialism and framentation in living as in entertainment, which explains why any intense experience must be "forgotten," "censored," and reduced to a very cool state before it can be "learned" or assimilated. [DOUBLE CHECK THE TRANSCRIPTION OF THIS CITATION]
[162-EM] {} ...specialist technologies detribalize. The nonspecialist electric technology retribalizes.
[164-EM] {} More and more we turn from the content of messages to study total effect... Concern with effect rather than meaning is a basic change of our electric time, for effect involves the total situaion, and not a single level of information movement.
[164-EM] {} The effect of electric technology had at first been anxiety. Now it appears to create boredom. We have been through the three stages of alarm, resistance, and exhaustion that occur in every disease or stress of life, whether individual or collective. [IMPORTANT NOTE: At least here, McLuhan sees stages of media change/transition as follows: 1. anxiety/alarm, 2. resistance, 3. boredom/exhaustion.]
[167-EM] {} ...it makes all the difference whether a hot medium is used in a hot or cool culture.
[170-EM] {} The stepping-up of speed from the mechanical to the instant electric form reverses explosion to implosion. In our present electric age the imploding or contracting energies of our world now clash with the old expansionist and traditional patterns of organization. [Mechanical-explosion, electrical-implosion]
[174-EM] {} ...media, as the extensions of man, are "make happen" agents, but not "make aware" agents.
[174-EM] {} These media, being extensions of ourselves, also depend on us for their interplay and their evolution. The fact that they do interact and spawn new progeny has been a source of wonder over the ages.
[175-EM] {} ...media. They are put out long before they are thought out. In fact, their being put outside us tends to cancel the possibility of their being thought of at all. [NOTE: Think of this is relation to the Dead Media Project.]
[177-EM] {} ...media as extensions of our senses institute new ratios, not only among our private senses, but among themselves, when they interact among themselves. Radio changed the form of the new story as much as it altered the film image of the talkies. TV... [includes more examples]