from marshall mcluhan, understanding media, pg. 24
the electric light escapes attention as a communication medium just because it has no 'content'. and this makes it an invaluable instance of how people fail to study media at all. for it is not till the electric light is used to spell out some brand name that it is noticed as a medium. then it is not the light but the 'content' (or what is really another medium) that is noticed. the message of the electric light is like the message of electric power in industry, totally radical, pervasive, and decentralized. for electric light and power are separate from their uses, yet they eliminate time and space factors in human association as exactly as do radio, telegraph, telephone, and tv, creating involvement and depth.