Can you tell me, what is the purpose of Zazen?
First, a bit on my background. I probably sat thousands of hours in total, was a staff member at a Zen Center where I taught zazen, and trained full-time in a Zen Monastic center for a year.
The practice of “Zazen”, as I explained before, is simply a highly ritualized ceremonial version of shikantaza “Silent Illumination” (Chinese: 默照禅), that is based in Dhyana (Sanskrit: ध्यान) or jhāna (Pali: 𑀛𑀸𑀦) .
Dhyana is often mislabeled as Meditation, however, it is more of an awakened state of mind in a non-abiding state ie: putting your mind in neutral gear so to speak with no particular destination or goal. The Buddha teaches the monks this method as to know their own defilements so they can ‘burn them up” — the relinquishment, renouncement and abandonment of them. In Tantra, the idea there is also to “burn out” defilements/desires though often through more controversial means.
The Indian Yogic method of the mirror-mind seems to have been found its way into Buddhism around 300 to 400 CE, this being a self-hypnotic trance-like state in which the brain is likely going into a waking non-REM sleep and the mind disassociates with the body (dream-like state).
You might be interested in the talk Mindfulness or Mindlessness by Robert H. Sharf in were he simply states that this current iteration of “Zazen” and Mindfulness that we see the Thervadans engage in through what is termed “Vipassana” is actually The Mahasi Technique developed in the 20th century! This also corresponds with what Nishiyama stated that prior to the 20th century, Japanese Zen monks never sat “Zazen” like they do in modern times.
So, my own humble opinion is that Dhyana most likely meant ‘being open-minded’ or to ‘put aside help opinions and conceptions’ and challenging the monk to view their own defilements of the mind. Later, this merged with Indian trance-like practices to become some sort of Sitting “communion with the deities” or “absorption” concept that we see in India, then later moved to become the ‘serene sitting’ shikantaza.
The Japanese variant takes the Chinese informal and casual shikantaza and formalizes it in to a highly ceremonial performance art called ‘Zazen’. Later in the 20th century, the Mahasi technique is adopted.
So, are there dangers with the The Mahasi Technique? Yes, many succumb to ‘Zen sickness’ also known as a dissociative disorder. Others suffer from major depression issues after prolonged sessions of this technique.
Others criticize the The Mahasi Technique as being rooted in non-conical materials, mostly from commentaries, and modern psychologists suggesting it may be nothing more than a joy-ride through ones own imagination in a tranced-out dream-like state of mind (Modern hypnosis).
Now, as for myself, given that the Vimalakirti Sutra states that this world right here and now is the Pureland, then I prefer to focus on what is ‘right in front of me’ and not drift away in tranced-out dream-like states of mind — and oh yes I experienced plenty of that sitting those thousands of hours facing a wall.