Freawaru wrote:Does, in this tradition, "included within a form realm" mean that one looses perception of the physical body and the external senses?
Yes. The Tibetan traditions rely on the Yogācārabhūmiśāstra and the Abhidharmakośa, which were composed during the same classical period of Indian Buddhist commentary as the Visuddhimagga, when abhidhamma terms and models had already become fairly standardized. Thus, the phenomenological descriptions of jhāna are similar. According to the Tibetan schools, one still experiences the physical and mental pliancy and bliss of the form realm in jhāna. Geshe Gedun Lodro, Calm Abiding and Special Insight:
- The yogic practitioner's body, to begin with, is an obstructive body, produced from past contaminated actions and afflictive emotions. Through the power of having cultivated meditative stabilization, the practitioner has made a form that is equal to the space of, and occupies the same area as, her or his obstructive body. Not only does the shadow-like pliancy pervade the entire body; it becomes of an undifferentiable entity with that body. Whatever potencies physical pliancy has arise for the body.
In Theravāda commentarial terms, the form portion of the "whole body" (sabbakāya) experienced in jhāna is mind-produced form which pervades the physical body. The Dīghanikāyaṭīkā:
- Mind-produced form (cittajarūpa) suffuses every area where there is kamma-produced form (kammajarūpa).
- Just as the bath-powder when inside and outside saturated with moisture, adheres and does not scatter, so the body of the meditator in the first jhāna is permeated with joy and pleasure from top to bottom, from the skullcap to the feet and from the feet to the skullcap, skin and hair, inside and outside. And he dwells without falling back. Thus he dwells like a Brahma god.
[Q.] Joy (pīti) and pleasure (sukha) are said to be formless phenomena (arūpa-dhamma). How then can they stay permeating the body?
[A.] Name (nāma) depends on form (rūpa). Form depends on name. Therefore, if name has joy, form also has joy. If name has pleasure, form also has pleasure.
Again, form born from joy causes tranquility of body, and when the entire body is tranquillized there is pleasure due to the tranquility of form. Therefore there is no contradiction.
Freawaru wrote:I am just trying to understand this in the light of the endless "jhana debate" (is one or is one not perceptive of the physical body and the external senses when in jhana ?).
It's a very ancient debate. One version of it is recorded right in the Abhidharmakośabhāsya. There were, and still are, sautrāntikas who maintain that the internal felt-sense of pleasure (sukha) experienced in jhāna is produced by internal winds within the body. The Abhidharmakośabhāsya:
- In the state of absorption, the body is penetrated by a wind born of excellent mental samādhi; this wind is tangible which is agreeably felt (sukhavedanīya) and is called well-being. Hence there is produced a tactile consciousness.
IMO this is just another way of trying to describe the same experience as described in the above quotations.
All the best,