Why is that Buddhist monks in China are the only vegetarians in the world of Buddhism even though they are living in a food culture whose historical antiquity and pluralism that few, if any, from any other part of the world can rival?
Cases in point, monks of Thailand and Japan, bhikkhus of Korea, lamas in Tibet, whether they are Mahayanists (the school of great vehicle), Theravadists (small vehicle) or even Vajrayanists (diamond vehicle or secret mantra), none of them has any monastic rules that inextricably linked to a strict vegetarian diet now being adopted by the Buddhist monks in China.
But before the reasons for such treachery are unfolded, let me first mark the fine line between vegetarianism as a monastic or ritualistic rules, zhai cai (齋菜) and vegetarianism as a dietary behavior, su cai (素菜). The distinction between the two is well worthwhile to point out to save confusion as we move onwards.
First and foremost, zhai cai is a dietary discretion affiliated to the practice of zhai jie (齋戒), which denotes the desistance (of something, e.g. meat, wine, sex or gamble) before a ceremony or rite. Similar to the practice of fasting in the West, it is meant to be strict and to serve mainly for religious and spiritual grounds. It should be noted however, the existence of zhai jie, and hence, eating zhai cai as a ritual has rooted in China well prior to the introduction of Buddhism. The abstinence of meat and wine before an ancestral veneration, as well as during the mourning period to manifest filial fidelity and respect has been a way of life ever since the Zhou dynasty (1045 - 256 BC).
Second, the dietary restrictions between the two is also different in the way that a herbivorous monk or nun must also avoid the consumption of the five acrid and pungent foods, as stated in Shurangama Sutra. They are, namely, onions, leeks, garlics, Chinese chives and shallots. The fetid five, also known in ancient times as the wu hun (五葷) are forbidden because their undesirable ability to arouse senses and temperament. Look closer and you will see that the character hun (葷) is a word with the radical "艸" atop, which suggest explicitly the vegetal origin of it. Taoist adepts of yore also try their best to avoid in contact with these five vegetables for a rather varied reason -- for them, anything provocative is undesirable for the physical well-being and spiritual development, and hence impedes their attainment of immortality.
Third, zhai jie can also be viewed to be a periodical fast, as in the case where Buddhist monks restrict their diet only in the morning. This shows another purpose of zhai jie: a discipline regimen aiding in meditation.
Vegetarianism as a diet, su cai on the other hand, aims to achieve benevolence and ahimsa (Sanskrit for non-violence) in a more liberal and flexible way than zhai cai does. The word "su" itself means plain, pure and simple so in its original sense it means to eat to modesty. This has proved to be popular among lay Buddhists and it is the concept used by vegetarian restaurants in general. One way or the other, it is inaccurate to label vegetarianism in China as simply as Buddhist cuisine since it can be a favored diet for Taoist and Confucianist too. (Edit: equally unfair for hippies and legion of PETA fans living in China as well).
Now that I've illustrated the difference between zhai cai and su cai, we're ready to survey the why question, that is, why vegetarianism has become the characteristic of Chinese Buddhism.
As we can easily imagine today, when Buddhism was first introduced to China from the "pure land of the West," as a strange religion without any foothold in a realm so foreign, the practice of alms was also imported from India to make sure the livelihoods of the monks are provided for. This tradition practically makes it impossible to be discriminating on the food one is receiving.
Even if we put down practicality and look solely on theoretical issues, we still cannot, contrary to common belief, find any mentioning of abstention of meat from the principal precepts of Buddhist ethnic imported from India. The closest one that might possibly have sowed the seed of a herbivorous land is the precept "thou shall refrain from taking life". However, this precept by itself should only cost a meat or guilt concern for butchers, fishmongers and etc. Certainly not monks or nuns as they are very unlikely to be the one who works in the slaughterhouse. In fact, there is one occasion, as depicted in the Jivaka Sutta, that Buddha declared the following when he was offered with meat in the alms he received:
... meat should not be eaten under three circumstances: when it is seen or heard or suspected (that a living being has been purposely slaughtered for the eater); these, Jivaka, are the three circumstances in which meat should not be eaten, Jivaka! I declare there are three circumstances in which meat can be eaten: when it is not seen or heard or suspected (that a living being has been purposely slaughtered for the eater); Jivaka, I say these are the three circumstances in which meat can be eaten.
As a result of this passage, many great buddhist teachers maintain that the consumption of san jing rou (三淨肉), or triply pure meat, is acceptable and compassionate not only for lay Buddhist but also for monks because it upholds perfectly the precept of ahimsa.
Of course, if this is how things are settled we won't be seeing any of the divergence we're witnessing today.
The controversy on strict vegetarianism for all Buddhists was first evoked by one of the most famous Buddhist kings in Chinese history, the Emperor Liang of Wu of the Southern and Northern dynasties (420 - 589 AD). In simple words, the ardent emperor had organized three Buddhist conventions in succession to push a bill that requires all Buddhist monks to be vegetarian.
The first two attempts proved to be embarrassing for the emperor because his Buddhist consultants were not thrilled at all and chose not to obey his solicitation. Meat-eating is in fine accordance with the spirit of Buddhist mercy, so these masters retorted. Yet, Emperor Liang of Wu managed to overcome the challenge by the third time around when he produced a sutra out of nowhere to validate the claim he advanced (out of nowhere because most scholars consider that particular sutra, Brahmajala Sutra, is fabricated by Chinese monks for the emperor to serve the particular ends -- the very first case of a "made in China" scandal).
It is very safe to say that Emperor Liang of Wu's effort was the major catalyst for the vegetarianism characteristic found in Chinese Buddhism.
As if this wasn't enough, the patronage of emperors and nobles from that era on also gave huge momentum for the propagation of Buddhism monasteries, at the expanse of the fine tradition of alms round. The frustration of an empty almsbowl simply vanished as by now most Buddhism monasteries are run in self-sufficiency with the vegetables grown on their own farms. There is account that shows vegetarian restaurants had made great strides as early as the Southern Song dynasty.
Still, one of the most beautiful things about Chinese Buddhism is how it evolved in dynamic conjunction with Chinese philosophical tradition. Time and again, we see that the concepts and values of Taoism and Confucianism are being assimilated into Chinese Buddhism, in which the development of vegetarianism is no exception when it echos with the beneficent views of Confucius. As Mencius once put it, "So is the superior man affected towards animals, that, having seen them alive, he cannot bear to see them die; having heard their dying cries, he cannot bear to eat their flesh." 孟子云：君子之于禽兽也，见其生，不忍见其死，闻其声，不忍食其肉。
The teachings of the six realms of samsaric existence that beings are born into are also reinforced by the ascendancy of Mahayanists, the predominate school of thoughts for Chinese Buddhism since Tang dynasty. Under this system, one realm is reserved for man and one for animal. The idea is that one's previous actions and thoughts determine which of the six realms one is reborn into. It follows that the change of roles in the next life is possible if one accumulate either merits or wrongs. This generates at least two karmic reflections: a) you don't kill, directly or indirectly a pig because you don't want to move down to the animal realm in your next life and b) it is possible that the very pork chop you're now munching come from someone you knew in previous life.
While all these religious and philosophical factors are reeling in the backdrop, we must not forget two important incidents taking shape in the front row: the invention of tofu and the Silk Road, both took place around the Han dynasty.
What distinguishes tofu apart from other plants and roots is that although it is a food derived from a pure vegetable source, it embodies a palpable meaty texture unseen in other vegetables. Leave it to the chefs to craft it in a multitude of forms, regular, pressed, tofu custard, whey skins, shredded chicken, shrimp or even a fish at wish. Whatever the concoction is, or mock meat for that matter, it helps to console the carnivore itch like no vegetable does.
On the other hand, numerous visits of envoy to the world outside China via the Silk Road since the eminent Zhang Qian of the Han dynasty, along with the expansion of imperial Han and Tang, from which new lands are brought, also helps flourish the importation of vegetables, whether it is transplanted or only as cut edibles, and so enriches the flavors of vegetarian cuisine in China. As histories told, walnut, burclover, pomegranate, grapes, sesame and coriander are among some of the greens brought by Zhang Qian. In due time, spinach was also introduced to China by Tang dynasty, sent by the king of Nepal -- then called by the Taoist "Persian herb," as a kind of cabalistic name. Kohlrabi, what we used commonly as pickled food, was also came into China through the Kansu corridor.
In conclusion, the view I would like to emphasize again is that the true beauty of a cuisine does not lies in recipes or exotic ingredients. To me it's always the cultural aspect of a food. In this respect, not only do we see the vigorous evolution of vegetarian cuisine in China, but also how it becomes the exemplification of kindness, modesty and compassion, the core virtues shared among Chinese Buddhism, Taoism and Confucianism.
