Every year at Arrow River we run a book study programme. This year the group wanted something to help them sort out the different Buddhist schools and so I suggested Peter Harvey's "Introduction to Buddhism" which takes a generally historical approach and attempts to cover the gamut of all branches of Buddhism. This book is widely used in colleges for the Buddhism 101 course.
This has led me to reflect on the diversity within Buddhism and how and why different sects arise in the first place. The proliferation of varieties of doctrine and practice is quite wide. And this seems to be a phenomenon that is not unique to Buddhism. All major religions have split into separate sects and the process seems to be on-going.
This is partly a natural result of geographical spread and consequent isolation, a factor particularly strong in Buddhism where land travel in Asia was always difficult. But this doesn't account for all splits by any means as for example in Japan which is a contained island culture with more sects than anywhere else and new ones happening all the time.
I think I can identify a few major causes of splits;
DOCTRINE - The special doctrine of the Buddha was anatta or sunyatta (no-self or voidness, the former being the special case and the latter the general case of the same basic principle.) This is a profound doctrine, difficult for beginners and in it's subtleties an ongoing source of speculation for the philosophers. Some of the breakaways seem to have been attempts to water down or domesticate the idea, this would be the case of the Puggalavadins and to a lesser degree the Yogacarins. The Madhyamika, on the other hand, seems to have been an attempt to radically confront the implications of the doctrine. The same could be said for the Avatamsa school from a different angle.
A related doctrinal issue is the nature of Nibbana or Nirvana and its relation to the conditioned world of Samsara. This is both transcendental and immanent, to purloin theological terms from another tradition. The early Buddhists, and the Theravada today, emphasize the transcendental aspect, the otherness, of Nibbana whereas the Mahayana emphasize the immanent aspect, its presence here-and-now and its fundamental non-separation from samsara. This very subtle doctrinal shift plays out in the difference between the Theravada Arahant ideal and the Mahayana Bodhisattva. The one seeks to escape the round of rebirth, the latter to play an active role in it for the benefit of beings.
VINAYA - The vinaya is the code for monks, regulating our behaviour in the world. Historically, disagreements over vinaya may have led to the very first split after the second council (this is historically debated.) It is still a cause of splits in the sangha in Theravada countries where separate ordination lineages exist which do not fully recognize each other (eg. Dhammayut and Mahanikay in Thailand). But it is not an issue which divides lay-people.
MEDITATION PRACTICE - Given the importance of meditation in Buddhist practice, it is surprising how little this has been a source of dispute. The Zen split into Rinzai and Soto is the only obvious example; the Rinzai (sudden enlightenment) called the Soto (gradual enlightenment) practice "sitting in a ghost cave."
Perhaps the emergence of Pure Land with its emphasis on "other power" could be classed as a practice issue as well.
SCRIPTURES - All the early schools had basically the same Sutta Pitaka but radically different Abhidhammas. This was not so much a cause of the splits but a symptom, as each attempted to explain their doctrinal positions precisely in their Abhidhamma texts.
With the emergence of Mahayana the scriptural issue comes to the forefront. The Theravada and other now extinct non-Mahayana schools never accepted the new scriptures as true "Buddha-vacana" or word of the Buddha. This is particularly problematic in the case of the Lotus Sutra which advocates some positions that the Theravada cannot accept and at the same time is venerated by some branches of Mahayana as the supreme text of all. The Nicheren chant Nam Ho Rengye Kyo translates as "Hail to the Supreme Lotus (Sutra)"
REFORM - In all religions there are periodic reform movements which arise to sweep away what they see as the accumulated corruption of centuries. Zen is in part a reform movement of this type. So is the Thai Forest Tradition although it never constituted a separate sect.
SYNCRETISM - Another repeated theme in the history of religions is the borrowing of ideas between religions. Tibetan Buddhism absorbed a big dose of Bon shamanism along the way. It's ancestor, Indian Tantric Buddhism, was already heavily syncretized with Hinduism. In China, there was much exchange of ideas with Taoism.
It's perhaps more speculative, but there is a possibility that Pure Land picked up some general tendencies from the Nestorian Christians who were present in China at the time. Nowadays in the West we see signs of syncretism with both New Age ideas and with western psychology. There is much speculation about the emergence of a new "Western Buddhism" but it is still way too early to know what shape it might take.
I'm sure other reasons for sectarianism could be found, but these are the major ones that have struck me so far. As a comparative note, we can see all of these operate in other religions as well. Doctrine about the nature of God, Jesus and the Trinity was a major source of division in early Christianity. Disputes about "vinaya" led to the emergence of the different monastic orders in that religion also. The issue of how strictly to apply the rules has also been the main cause of division within Judaism. Reform movements (in the sense outlined above) would include Protestantism and Wahabbism (movements which share many other features also, but that's a matter for another blog perhaps). Other religions have also seen new scriptures causing breakaway sects, think of the Mormoms. And syncretism is everywhere from pagan survivals in Christianity like the date of Christmas to Jewish borrowings from Babylon like the story of the flood.
In fact, Buddhist influences on Christianity have been much commented on. The birth story of Jesus, for instance, parallels in some details that of the Bodhisatta. In particular, the wise man noticing signs on the infant and despairing that he would not live to see the child grown.
Is the division of Buddhism into sects a good thing? That's a useless and naive question, it is as it is. The essence of the Dharma is pure and incorruptible but it is carried by human vessels who are not. Perhaps by having the internal light reflected from different angles we may get a better chance of catching the original beam.