Editing Marshall McLuhan (section)

== Key concepts ==
=== Tetrad of media effects ===
{{Main|Tetrad of media effects}}

In ''Laws of Media'' (1988), published posthumously by his son [[Eric McLuhan|Eric]], McLuhan summarized his ideas about [[media studies|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.<ref name="LAC" />

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'' and ''Reversal'' qualities, both ''Ground'' qualities.{{sfn|E. McLuhan|1998|p=28}}

[[File:MediaTetrad.svg|right|thumb|250px|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 ===
{{Main|Figure and ground (media)}}

McLuhan adapted the [[Gestalt psychology]] idea of a ''figure and a ground'', which underpins the meaning of "the medium is the message."<!--"message" is correct here--> 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.<ref name="LAC" />

All technologies have embedded within them their own assumptions about [[Time- and space-bias|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.<ref name="LAC" />

===Opposition between optic and haptic perception===

In McLuhan's (and [[Harley Parker]]'s) work, electric media have an affinity with [[Haptic perception|haptic]] and hearing perception, while mechanical media have an affinity with visual perception. This opposition between optic and haptic had previously been formulated by art historians [[Alois Riegl]] in his 1901 ''Late Roman Art Industry'', and by [[Erwin Panofsky]], in his 1927 ''Perspective as Symbolic Form''.

In his ''[[The Work of Art in the Age of Mechanical Reproduction]]'' (1935), [[Walter Benjamin]] observed how, in perceptions of modern Western culture, from about the 19th century a shift began from the optic toward the haptic.<ref>Pinotti, Somaini (2016) Cultura visuale, p.86</ref> This shift is one of the main recurring topics in McLuhan's work, which McLuhan attributes to the advent of the electronic era.