Can we use Piti as a meditation subject? There are 40 meditation objects are given in Visuddhimagga as follows. Ten recollections; ten foul objects; ten kasinas; four sublime abidings; four formless absorptions; one resolution into elements; and one perception of the filthiness of food. My question is whether we can keep four form absorptions as a meditation objects, but specifically Piti as a meditation object.
Anything can be used as an object of meditation. Hell, you could use a chocolate cake if it tickled your fancy. But just because you can use anything, it doesn't mean that you should. The best objects are those that are consistent, stable, repeatedly accessible, and don't give rise to additional mental formations. The breath is most often used because it checks all of those boxes quite easily. Piti can meet those same requirements, but until you hit the 1st jhana, it is entirely too unstable and inconsistent. It can also give rise to clinging and attachment which would ultimately prevent you from moving past the 2nd jhana.
Similar to dishonesty about attaining jhana, clinging to rapture & jhana leads to rebirth in hell. Therefore, the Lord Buddha did not teach those who have unshakeable permanent faith in Him to "keep rapture" as meditation object. Instead, the Buddha taught those with unshakeable permanent faith to view impermanent alien diseased rapture with Right View.
There is the case where an individual, withdrawn from sensuality, withdrawn from unskillful qualities, enters & remains in the first jhana: rapture & pleasure born from withdrawal, accompanied by directed thought & evaluation. He savors that, longs for that, finds satisfaction through that. Staying there — fixed on that, dwelling there often, not falling away from that — then when he dies he... goes to hell
There is the case where a monk, secluded from sensuality, secluded from unskillful qualities, enters & remains in the first jhana: rapture & pleasure born of seclusion, accompanied by directed thought & evaluation. He regards whatever phenomena there that are connected with form, feeling, perception, fabrications & consciousness, as inconstant, stressful, a disease, a cancer, an arrow, painful, an affliction, alien, a disintegration, an emptiness, not-self. He turns his mind away from those phenomena, and having done so, inclines his mind to the property of deathlessness: 'This is peace, this is exquisite — the resolution of all fabrications; the relinquishment of all acquisitions; the ending of craving; dispassion; cessation; Unbinding.'
Teachers like ie Leigh Brasington teach directing attention away from the breath to a pleasant sensation when such a feeling has spawned so that it may grow in intensity.
One can't just use joy as a meditation because it has to be brought about by directing the mind to a theme for the purpose of joy and withdrawing from the theme when achieved.
Also piti is only a factor in the 1st and the 2nd jhanas (by 4 fold classification). The 3rd and the 4th are without piti.