ate in his career, having been repeatedly criticized for failing to provide a scientific basis for his thought, McLuhan reworked his ideas about media and technology in a sequel to Understanding Media in collaboration with his son Eric. The new book, titled Laws of Media: The New Science (1988), was published eight years after McLuhan’s death. In it, McLuhan and Son offer

ow to disprove them? By finding any case where they do not apply or a case which might require a fifth law.

The McLuhans intend their four laws to apply to all media. And to invite the application of these laws to as wide a variety of humankind’s endeavors as possible, they offer them not as statements but rather as questions:

Remember, these laws are not limited to media of communication; they apply to any artifact, anything of human construction, including language and systems of thought, as we will see below…

For “extend,” in the phrasing of the first law, we may substitute “enhance,” “intensify,” “make possible,” or “accelerate,” depending on the case.

A refrigerator enhances the availability of a wide range of foods.

Perspective in drawing and painting intensifies a single point of view.

A photocopier makes possible the reproduction of texts at the speed of the printing press.

The computer accelerates the speed of calculations and retrieval of information.

Obsolescence is a consequence of extension. When a medium fulfills its function of extending the body or replacing another medium, parts of the environment of whatever was extended become obsolete. For example:

When the car replaced the horse, it did away with stables, blacksmiths, saddlemakers, harness-menders, hitching posts, horse troughs, carts, and stagecoaches.

Older structures and environments or older forms of action, human organization, and thought are revived by the introduction of a new medium. For example:

A dinner table retrieves the picking and choosing options surrendered by early humans, who discovered in the lap a site for isolating, manipulating, and defending their food.

Feminism, in its extremist form, retrieves the corporate identity of matriarchal society.

When a technology is pushed to its limit, as when media are overheated or overextended, it can either take on the opposite of its original features or create the opposite of its intended function. For example:

A dinner table, if very large, no longer offers the ease of reach for which tables were originally designed.

If overcrowded, the dinner table can reverse from a place for sharing food into a site where table mates aggressively intrude on each other’s space.

n describing how the laws of media interact, the McLuhans reveal a dynamic pattern of interlocking effects typical of any technology or human construct. In the form of a diagram called a tetrad, the four laws can be shown as follows:

Extension and obsolescence are linked as action to reaction, which is not the case for retrieval and reversal. A medium does not reverse into its opposite because some older form has been retrieved; rather, it reverses because it is pushed to its limit.

he complementary qualities of these laws can be seen when they are taken in pairs, either horizontally or vertically. Some examples:

Alcohol extends energy but reverses into depression.

The car extends individual privacy but reverses into the corporate privacy of traffic jams.

Earth-orbiting satellites extend the planet and retrieve ecology.

Cubism makes visual space obsolete and reverses into the nonvisual.

The microphone makes private space obsolete and reverses into collective space.

s there a sequence to the laws of media? Obsolescence is a direct and immediate consequence of extension, but one might expect the process of retrieval to take effect only later. For example, with the advent of radio, telegraph wires and connections disappeared almost immediately; the resulting rekindling of tribal warfare took a little longer. As for reversal, it would seem to set in only when a medium has been in use long enough to have been overextended. All this would suggest that an order imposes itself on the laws of media, but the McLuhans stress that this is not the case:

There is no “right way to ‘read’ a tetrad,” they note, because “the parts are simultaneous” (p. 129).

he arrangement of the four laws of media relative to each other, as given above, applies to the following examples. They are labelled for the case of WINE but indicated only by the same relative positions for the others. (Don’t forget that reversal can be either a reversal of function or a reversal into an opposite form, depending on the case involved; all the examples given below refer to the latter.)

Here’s a four-pack of tetrads, straight from the McLuhans: