you ask very good questions, but this time I am stumped. MN 118 is a sutta I stay away from, kind of, becauseJust a general question on jhana: I've read several commentaries on the four tetras of anapanasati which suggest the first three tetrads are for developing jhana.
Is this basically correct?
people interpret it in various ways. My first understanding is, it is an elaboration of the Satipathana bhavana. Pl note I say S. bhavana and not establishing mindfulness merely. Unlike many other Theravadins I have come to understand the Satipatthana bhavana as a different approach to cessation. Cessation meaning the state of mind where one is not conceiving anymore. Sometimes it is called emptiness, or the void.
So to answer your question, (I just read the sutta, to jog my memory). I think one can safely say the four tetrads also relate to the four jhanas.
They are all trying to accomplish the same thing.
What disturbs me about this sutta is, that some think focussing on the breath is the "be all and end all" of the
sutta. It is definitely not, based on my understanding.
Breath is brought in, as an aspect of vitaka, vicara of the first jhana.
It might be the influence of Upanishads that some describe breath as almost "a Pranayama practice", i.e. control of breath, or as an object to begin with.
All these meditations (samma sati, same samadhi) are objectless meditations. If one's consciousness is trapped in breath, or an object, how can one release the mind/consciousness? The whole point of practice is the release of the mind/consciousness, the release of "I", it is only then
that one does not conceive.
You have asked a couple of questions in other threads, in the past, that helped me a whole lot. So thank you dear stargazer! for your curious mind