Was just reading an essay by McLuhan that was released in more complete form as a book in the early 90s called “Laws of Media.” In it McLuhan presents the four basic questions for examining any medium:
a) What does it enhance?
b) What does it obsolesce?
c) What does it retrieve that had been obsolesced earlier?
d) What does it flip into when pushed to the limits of its potential?
Because like most things McLuhan it’s fairly complicated, the examples help quite a bit. Take this one for the spoken word:
a) [Enhances:] “Speak that I may see thee.” (Title of book by Harold Stahmer);
b) Obsolesces the subhuman;
c) Retrieves past experience;
d) [Flipped into when pushed to limits:] Group awareness and class structure.