Saṅkhara in Ānāpānasati
What is saṅkhara in the particular case of Anapanasati ?
One should refer to both SN 22.81, and its parallel SA 57 (translated by Analayo).
What these two texts are teaching us, and have in common, is that:
1. We should "well contemplate the aggregates, that is, [based on cultivating] the four establishments of mindfulness, etc..."
What purport to us here then, is how we should contemplate the aggregate saṅkhara in Anapanasati.
2. That "contact with ignorance gives rise to craving. In dependence on craving, this saṅkhara arises".
- Ignorance is what we haven't discovered yet. It is a non-discerment.
- Contact (phasso) is just the "transfer of property" from one thing to another.
When one, in Anapanasati comes, through the body that is breath, to a desired feeling of contentment (piti,) born of mano - (sikkhati is a desiderative verb, that means "to desire to be able to" - and also patisamvedi has the underlying meaning of: "to have the knowledge of the particulars of a thing).
And when one desires also to be able to know the particulars of sukha; and experiences it, THEN there is contact.
The part of samadhi that corresponds to the commingling (saṅkhara) of mano with citta is contact.
Because one transfers the property of kaya's piti, acquired through and within mano; and because one doesn't discern yet the duality in the commingling (saṅkhara) ; because there is not yet Vi-ññāṇa - One is ignorant of the duality of sukha. One mixes up the piti/dukkha of mano's piti, with the bliss of citta. For this commingling, this aggreagate that is saṅkhara is dukkha, - because it is not one's ownness (the second meaning of anicca); it is not our self (anatta).
Experiencing and calming cittasaṅkhara in the seventh & eighth steps of Ānāpānasati, is just about that. And calming the saṅkhara is calming the commingling, the synergy. Calming piti and calming sukha. Like one calms both sides of one's breath and the kayasaṅkharā.
The etymology of saṅkhara (संकर saṃkara [act. saṃkṝ] [√ कॄ kṝ] ,) shows a meaning of "commingling", with an under lying sense of confusion.
The discernment is to see that this mano's piti + citta's sukha is indeed dukkha.
One has first to liberate the citta (from mano);
then one has to abandon this pain/pleasure of mano/citta, once in the fourth jhana.
Sukha is not really bliss. It is polluted bliss, as long as citta is not totally liberated.
When it "mixes" with the body, through mano, it becomes sukhañca kayena (Third jhana).
The Sanskrit रननाप manāpa [mana_āpa] means lit. “reach the manas”.
So what is agreeable (manāpa,) or disagreable (amanāpaṃ) , or both ( manāpāmanāpa,) seems to be related to “reaching the mano”. (See MN 152).