Of all the Internet searches that end up at the McLuhan Program website and weblog, the search for the meaning of the famous "McLuhan Equation" is the most frequent. Many people presume the conventional meaning for "medium" that refers to the mass-media of communications - radio, television, the press, the Internet. And most apply our conventional understanding of "message" as content or information. Putting the two together allows people to jump to the mistaken conclusion that, somehow, the channel supersedes the content in importance, or that McLuhan was saying that the information content should be ignored as inconsequential. Often people will triumphantly hail that the medium is "no longer the message," or flip it around to proclaim that the "message is the medium," or some other such nonsense. McLuhan meant what he said; unfortunately, his meaning is not at all obvious, and that is where we begin our journey to understanding.

Marshall McLuhan was concerned with the observation that we tend to focus on the obvious. In doing so, we largely miss the structural changes in our affairs that are introduced subtly, or over long periods of time. Whenever we create a new innovation - be it an invention or a new idea - many of its properties are fairly obvious to us. We generally know what it will nominally do, or at least what it is intended to do, and what it might replace. We often know what its advantages and disadvantages might be. But it is also often the case that, after a long period of time and experience with the new innovation, we look backward and realize that there were some effects of which we were entirely unaware at the outset. We sometimes call these effects "unintended consequences," although "unanticipated consequences" might be a more accurate description.

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McLuhan tells us that a "message" is, "the change of scale or pace or pattern" that a new invention or innovation "introduces into human affairs." (McLuhan 8) Note that it is not the content or use of the innovation, but the change in inter-personal dynamics that the innovation brings with it. Thus, the message of theatrical production is not the musical or the play being produced, but perhaps the change in tourism that the production may encourage. In the case of a specific theatrical production, its message may be a change in attitude or action on the part of the audience that results from the medium of the play itself, which is quite distinct from the medium of theatrical production in general. Similarly, the message of a newscast are not the news stories themselves, but a change in the public attitude towards crime, or the creation of a climate of fear. A McLuhan message always tells us to look beyond the obvious and seek the non-obvious changes or effects that are enabled, enhanced, accelerated or extended by the new thing.

McLuhan defines medium for us as well. Right at the beginning of Understanding Media, he tells us that a medium is "any extension of ourselves." Classically, he suggests that a hammer extends our arm and that the wheel extends our legs and feet. Each enables us to do more than our bodies could do on their own. Similarly, the medium of language extends our thoughts from within our mind out to others. Indeed, since our thoughts are the result of our individual sensory experience, speech is an "outering" of our senses - we could consider it as a form of reversing senses - whereas usually our senses bring the world into our minds, speech takes our sensorially-shaped minds out to the world.

But McLuhan always thought of a medium in the sense of a growing medium, like the fertile potting soil into which a seed is planted, or the agar in a Petri dish. In other words, a medium - this extension of our body or senses or mind - is anything from which a change emerges. And since some sort of change emerges from everything we conceive or create, all of our inventions, innovations, ideas and ideals are McLuhan media.

Thus we have the meaning of "the medium is the message:" We can know the nature and characteristics of anything we conceive or create (medium) by virtue of the changes - often unnoticed and non-obvious changes - that they effect (message.) McLuhan warns us that we are often distracted by the content of a medium (which, in almost all cases, is another distinct medium in itself.) He writes, "it is only too typical that the "content" of any medium blinds us to the character of the medium." (McLuhan 9) And it is the character of the medium that is its potency or effect - its message. In other words, "This is merely to say that the personal and social consequences of any medium - that is, of any extension of ourselves - result from the new scale that is introduced into our affairs by each extension of ourselves, or by any new technology."