Except for light, all other ...

Except for light, all other media come in pairs, with one acting as the \
Except for light, all other media come in pairs, with one acting as the "content" of the other, obscuring the operation of both.

Quotes from the same author

Today's child is bewildered when he enters the 19th century environment that still characterizes the educational establishment where information is scarce but ordered and structured by fragmented, classified patterns subjects, and schedules.
Advertising is the greatest art form of the 20th century.
If the nineteenth century was the age of the editorial chair, ours is the century of the psychiatrist's couch.
Our Age of Anxiety is, in great part, the result of trying to do today's job with yesterday's tools and yesterday's concepts.
Invention is the mother of necessities.