Understanding Media: Extensions of Man is a critical analysis of media studies which offers a new approach. McLuhan argues that for too long media studies has been distracted by the content of media rather than how it is brought to viewers. He believes, controversially, that content is not nearly as important as the mediums through which media is conveyed. Many of his contemporaries were arguing that content was central. A major focus has been on whether or not violence in media is impacting children or how subliminal messaging about drugs and alcohol is brought to teenagers. However, McLuhan takes a new approach and considers the mediums of technology themselves and the varying effects they have on the viewer.

McLuhan believes technology to be extensions of humans. The first technology he considers is human speech. He writes that this is the original form of media and that it is what all other forms of technology are built off of. He generally writes positively of physical forms of technology. For example, he seems to believe that technology, such as bicycles and light bulbs have revolutionized media. While these mediums have no content, they have changed the ways we are able to consume content. For example, bicycles revolutionized newspaper routes, and light bulbs created a sense of space at night that was night quite as possible before.

However, McLuhan writes generally negatively about electronic technologies that are used to expand consciousness. Understanding Media is most well known for its distinctions between “hot” and “cool” mediums. McLuhan makes clear that these are not definitive categories and depend greatly on the culture and context of where they are introduced. Hot mediums have limited viewer participation. For example, a movie theater is quiet and dark. There is little to distract you than the movie itself. Cool mediums have increased viewer participation. McLuhan gives the telephone as an example of this medium, because the telephone is a two way conversation that requires participation.