I will invite the pundits to explain this further, as I'm not very scholarly and am still a beginner in the Buddha's teaching, but I think we really need to stop translating sati as 'mindfulness' altogether, and just refer to it as 'recollection' or 'remembrance' which I've read is a more accurate description. I'm sorry I don't have the energy to hunt down where I read it.
As far as 'knowing' or 'perceiving' the breath goes, 'pajanati' which would appear to derive from 'sampajanna' seems to refer to this...maybe the 'knowing' or awareness itself
is sampajanna ('clear comprehension?), and the quality of recollection, of remembering where you are and what you are doing
, is sati...? sati and sampajanna work together, but they have distinct funtions, yes?
I invite some clarification here...but I think that the way we translate these terms, as Enlish speakers, influences how we understand them, and our practice, for better or for worse.
In Ānāpānasati/Satipaṭṭhāna work, sati
is part of the reflexive determination to stay on-task with the object of contemplation. We find this in the Ānāpānasati Sutta where in the setting up of practice the practitioner is advised to keep mindfulness set forward
while mindfully breathing in and out (parimukhaṃ satiṃ upaṭṭhapetvā so satova assasati, sato passasati
). We find a strengthening of this definition of sati
in the Satipaṭṭhāna Sutta where the task of sati
is connected with ātāpa
(ardour or intense endeavor) and sampajāna
(clear-knowing). Here sati
keeps one on-task with the object of contemplation, and sampajāna
(clear-knowing, which is a further refinement of direct-knowing in pajānāti
) examines everything rising and falling with that object with passive examination as we read in the refrain of insight
of this sutta
"Thus he lives contemplating the body in the body internally, or he lives contemplating the body in the body externally, or he lives contemplating the body in the body internally and externally. He lives contemplating origination-things in the body, or he lives contemplating dissolution-things in the body, or he lives contemplating origination-and-dissolution-things in the body. Or indeed his mindfulness is established with the thought: 'The body exists,' to the extent necessary just for knowledge and remembrance, and he lives independent and clings to naught in the world."
...as examination of the satipaṭṭhānas' progress.
Katamo ca bhikkhave asaṅkhatagāmī maggo: samatho ca vipassanā ca. Ayaṃ vuccati bhikkhave asaṅkhatagāmī maggo.
“And what, bhikkhus, is the path leading to the unconditioned? Calm and insight
. This, bhikkhus, is called the path leading to
the unconditioned.” SN. 43.2 – Samathavipassanāsuttaṃ Secure your own mask before assisting others
. – NORTHWEST AIRLINES (Pre-Flight Instruction)A Handful of Leaves