You quote from the video, which I confess I haven’t watched (though I did look at the PowerPoint slides):
The later Buddhaghosa understanding of jhana is you’re aware of a subtle mental image and you are no longer aware of your physical body and you’re no longer aware of mental activity beyond being aware of the subtle mental image.
So within the Thai forest tradition, there’s been research that has shown that that’s probably a later development. You don’t find that teaching in the early teachings in the Samyutta Nikaya.
I’m surprised that I can relate to the description you ascribe to Buddhaghosa. Take me just a little background to explain how.
You are not your body, but you are the consciousness in the body, because of which you have the awareness of “I am”. It is without words, just pure beingness. Meditation means you have to hold consciousness by itself. The consciousness should give attention to itself.
(Gaitonde, Mohan [2017]. Self – Love: The Original Dream [Shri Nisargadatta Maharaj’s Direct Pointers to Reality]. Mumbai: Zen Publications. ISBN 978-9385902833)
From my writing:
I used to talk about the location of consciousness, but a friend of mine would always respond that for him, consciousness has no specific location. As a result, I switched to writing about the placement of attention:
“There can… come a moment when the movement of breath necessitates the placement of attention at a certain location in the body, or at a series of locations, with the ability to remain awake as the location of attention shifts retained through the exercise of presence.”
In his “Genjo Koan”, Dogen wrote:
When you find your place where you are, practice occurs, actualizing the fundamental point.
(“Genjo Koan [Actualizing the Fundamental Point]”, tr. Robert Aitken and Kazuaki Tanahashi, from “Moon in a Dewdrop: Writings of Zen Master Dogen”, p 69, © San Francisco Zen Center)
Given a presence of mind that can “hold consciousness by itself”, activity in the body begins to coordinate by virtue of the sense of place associated with consciousness. A relationship between the free location of consciousness and activity in the body comes forward, and as that relationship comes forward, “practice occurs”. Through such practice, the placement of consciousness is manifested in the activity of the body.
Now the key thing is, that the experience of consciousness at a singular location can be peculiar, as though a location in open space.
Nevertheless, I think “subtle image” is a bad description. The crucial transition is in Dogen’s second statement:
When you find your way at this moment, practice occurs, actualizing the fundamental point…
(ibid)
“When you find your way at this moment”, activity takes place solely by virtue of the free location of consciousness. A relationship between the freedom of consciousness and the automatic activity of the body comes forward, and as that relationship comes forward, practice occurs. Through such practice, the placement of consciousness is manifested as the activity of the body.
Not so much that “you are no longer aware of your physical body and you’re no longer aware of mental activity beyond being aware of the subtle mental image”, as that the singular location of consciousness associated with the singular sense of self comes forward, body and mind are still there but consciousness can take place freely and the activity of the body in inhalation and exhalation follows from the free location of consciousness.
A different sense of mind and body.