Web Theory - Marshall McLuhan (Study Task 06): Tetrad

In Laws of Media (1988), McLuhan summarized his ideas about media in a concise tetrad of media effects. The tetrad is a means of examining the effects on society of any technology (i.e., any medium) by dividing its effects into four categories and displaying them simultaneously. McLuhan designed the tetrad as a pedagogical tool, phrasing his laws as questions with which to consider any medium:

What does the medium enhance?
What does the medium make obsolete?
What does the medium retrieve that had been obsolesced earlier?
What does the medium flip into when pushed to extremes?

The laws of the tetrad exist simultaneously, not successively or chronologically, and allow the questioner to explore the "grammar and syntax" of the "language" of media. McLuhan departs from his mentor Harold Innis in suggesting that a medium "overheats", or reverses into an opposing form, when taken to its extreme.

Visually, a tetrad can be depicted as four diamonds forming an X, with the name of a medium in the centre. The two diamonds on the left of a tetrad are the Enhancement and Retrieval qualities of the medium, both Figure qualities. The two diamonds on the right of a tetrad are the Obsolescence andReversal qualities, both Ground qualities.

A blank tetrad diagram

Using the example of radio:
Enhancement (figure): What the medium amplifies or intensifies. Radio amplifies news and music via sound.
Obsolescence (ground): What the medium drives out of prominence. Radio reduces the importance of print and the visual.
Retrieval (figure): What the medium recovers which was previously lost. Radio returns the spoken word to the forefront.
Reversal (ground): What the medium does when pushed to its limits. Acoustic radio flips into audio-visual TV.
Figure and ground


McLuhan adapted the Gestalt psychology idea of a figure and a ground, which underpins the meaning of "The medium is the message." He used this concept to explain how a form of communications technology, the medium or figure, necessarily operates through its context, or ground.

McLuhan believed that in order to grasp fully the effect of a new technology, one must examine figure (medium) and ground (context) together, since neither is completely intelligible without the other. McLuhan argued that we must study media in their historical context, particularly in relation to the technologies that preceded them. The present environment, itself made up of the effects of previous technologies, gives rise to new technologies, which, in their turn, further affect society and individuals.

All technologies have embedded within them their own assumptions about time and space. The message which the medium conveys can only be understood if the medium and the environment in which the medium is used—and which, simultaneously, it effectively creates—are analysed together. He believed that an examination of the figure-ground relationship can offer a critical commentary on culture and society.