It took 65 years after the invention of the printing press for someone to decide that putting page numbers on books was a good idea! The essay took a century to be invented; thus it is quite likely that the enduring and serious forms of the new media have not been invented -- we are still mired in the imitation of the old: paper, film, and tape.
We can see this most clearly by recognizing that a special computer medium for serious argumentative discourse has not yet appeared. Most "multimedia" today are collages that are more like multidimensional comic books and romance novels than carriers of serious discourse.
Literacy is more than being able to read a streetsign or write a party invitation -- it is about being fluent in the ideas and issues of humankind and being able to use and create symbolic representations to understand and explore them further. The pressing issues of the 21st century will require new carriers of serious discourse that will be as large a step from the essay and classical mathematics as those were from collections of proverbs.
We are certain that a "superessay" is possible and inevitable because many of its properties can be anticipated. For example, many of the most serious issues of the next century will involve complex nonlinear systems such as the atmosphere, the rain forests and other bioenvironments, the population explosion, economics, epidemics such as AIDS, and perhaps most important the kinds of social systems that can best achive a balance between stability and individual freedom. These are not easily explained, argued about, or understood in terms of day-to-day language or classical mathematics. But many of their most important characteristics can be dynamically modeled and explored on the computer. Even more important, a "feel" -- an "uncommon sense" -- about how these systems behave and what should be heeded can be attained, even at an early age, by building simulation models and learning to think in systems and simulation terms.
The most important media of the 21st century will provide the framework for the next level of human thought. The most important learining of the 21st century will be to develop our abilities to conceive, represent, and ponder this next step up the mountain.