There was a most remarkable change in the character of Chinese Zen practice around the turn of the First Millennium that is not generally discussed very much. Not to be pedantic or unnecessarily academic, but it's worth considering as we seem to be going through a modern counterpart.
According to DT Suzuki's introduction to RH Blyth's 1966 translation of the Mumonkon (the Gateless Gate collection of koans), during the T'ang dynasty there were no koans because each student brought his own questions, philosophical or spiritual, to the master. The master then dealt with the troubled student in the way he thought best. Zen was, in those days, "full of vigor and creativity," according to Suzuki.
During this Classical Period of Chinese Zen, traveling monks verbally spread and exchanged news of enlightened teachers throughout the country, and famous Zen teachers of this era created public sensations when they traveled from one place to another. Zen of the Classical Period possessed a verdant oral tradition, which was served and sustained by a developing literary tradition.
History tells us that in the year 907, the T'ang dynasty ended and China entered an era of political upheaval. The subsequent period of the Five Dynasties in Northern China and Ten Kingdoms in Southern China was somewhat analogous to Japan's later and tumultuous Kamakura Period. With the decline and fall of the T'ang dynasty, the Classical Period also ended and Chinese Zen lost its original vitality. Suzuki notes that the age of creativity gave way to an age of recollection and interpretation.
In 960, Emperor Taizu reunified China, ushering in the Song dynasty (960 - 1279). Zen masters of the Song dynasty relied less on spontaneous exchanges with their students and each other and more on study of the recorded exchanges (koans) of the T'ang dynasty masters. This evolved into the formal koan system of study whereby the students were trained to apply themselves to the solutions of "cases" left by the old T'ang masters. Clearly abandoning all pretense of the former avoidance of written words, the Song masters instead embraced them. In the past, Zen teachers had influenced the writers and poets but beginning in the Song, the Zen teachers became the writers and the poets. While some teachers opposed this trend, the new literature of enlightenment was too beautiful for most to eschew.
Despite all the dazzling technological advances of the Song Dynasty, a tendency to idealize the T'ang past infected Zen culture no less than it did other areas of Song culture and politics, as Andy Ferguson notes in Zen's Chinese Heritage. The near mythification of earlier Classical Period Zen masters occurred during the Song and the later Literary Period of Chinese Zen. The Classical masters would most likely have never tolerated their creative and vigorous responses to their students' questions systematized into a recorded curriculum to be scrutinized and studied by later generations, who would have their own and different questions, problems, and troubles, although Zen has now become a more or less systematized teaching based on those very recorded questions and answers.
The question is how this came to happen. Was it the result, some 1,500 years after the life of Shakyamuni Buddha, of the decline of the dharma, the start of the so-called mappō era when practice and enlightenment are no longer attainable? Although some during the life of Zen Master Dogen (who visited China during the late Song) believed that this period had begun in the year 1052, Dogen himself refuted that view and stated that it was only an expedient teaching intended to encourage monks to practice harder while they were still alive.
Was it the result of new technology? Among the many advances during the Song Dynasty was the invention of movable type printing, which allowed books to be printed faster and more cheaply than handwritten texts. Could the ready availability of the koan collections in print have reached a wider audience than the one-on-one interviews among teacher and student, and did the teachers have to then adopt their styles to fit the new medium?
Was it the result of social changes? During the Song Dynasty, the populace engaged in a vibrant social and domestic life. There were entertainment quarters in the cities that provided a constant array of amusements, including theater, puppeteers, acrobats, storytellers, singers, musicians, and prostitutes. There were tea houses, restaurants, and organized banquets in which to relax. People attended social clubs in large numbers, including tea clubs, exotic food clubs, antiquarian and art collectors' clubs, poetry clubs, and music clubs. With all of these options for entertainment and diversion, who had time to attend a lecture by some visiting Zen master, as opposed to reading the quotes of past masters?
Still, among the monks and masters, even though the subject of study had become the recorded koans of the past, the teachers helped the students understand the nuances and meanings of the koans and stories, and encouraged them to realize the dharma for themselves. The true understanding of the koans can not be grasped through intellect or logic, and the teachers both encouraged ardent pursuit of the meaning while simultaneously discouraging assumptions of having quickly and easily grasped the subtle nuances contained in the record.
Today, a millennium or so after this shift in the style and content of Zen practice, we're experiencing even more accelerated technological advances than could even have been dreamed of by the Song Chinese. The automobile and jet airplanes allow us too travel with great ease and leisure to visit teachers and masters from all over the globe, and it is no longer at all unusual for masters to travel around the world to disseminate their teachings. Television and radio carry the word even faster, so that the physical presence is so longer required for the teaching to be spread, and the internet can carry teachings, commentary, and a countless, almost bewildering array of viewpoints to all corners of the planet. Technology has allowed videos and podcasts to convey the teachers tone of voice and subtle nuances that might be lost in the printed word, even if the "print" is only on a flat-screen monitor, and Skype and internet chat rooms allow long-distance, interactive "conversations" between teachers and students.
It remains to be seen what effect all this technology has on the style and content of Zen practice. If whatever combination of the political, social, and technological changes that marked the transition from the T'ang to the Song dynasty resulted in the major differences between the Classical and the Literary Periods of Chinese Zen, what will come of the transformative global changes experienced now? Will it render quaint traditional practices of monastic retreat to study with a master and one-to-one transmission of the teaching? Will the access to teachings and wisdom from so many cultures and traditions result in an increased syncretization of Buddhism and an obsolescence of older schools? And most importantly, will enlightenment and awakening still be possible under these conditions?
The effects of this grand, global experiment on Zen practice have yet to be seen.