Nyanaponika Thera on the Inter-relations of the Four Sublime States

Question

I'm wondering about older sources for some of what Ven. Nyanaponika Thera says in this essay:

• The Four Sublime States: Contemplations on Love, Compassion, Sympathetic Joy and Equanimity.

For some of the claims, it's easy for me to realize what older text he's referencing - for instance his claims about why they are called sublime you can trace to Vism. IX 105.

But specifically for his claims about how the four sublime abidings all suffuse each other, I'm having a harder time thinking of an older reference. Anyone know one? Or should these be categorized as his own claims?

The passages I'm thinking of are these ones:

"How, then, do these four sublime states pervade and suffuse each other?

Unbounded love guards compassion against turning into partiality, prevents it from making discriminations by selecting and excluding and thus protects it from falling into partiality or aversion against the excluded side.

Love imparts to equanimity its selflessness, its boundless nature and even its fervor. For fervor, too, transformed and controlled, is part of perfect equanimity, strengthening its power of keen penetration and wise restraint.

Compassion prevents love and sympathetic joy from forgetting that, while both are enjoying or giving temporary and limited happiness, there still exist at that time most dreadful states of suffering in the world. It reminds them that their happiness coexists with measureless misery, perhaps at the next doorstep. It is a reminder to love and sympathetic joy that there is more suffering in the world than they are able to mitigate; that, after the effect of such mitigation has vanished, sorrow and pain are sure to arise anew until suffering is uprooted entirely at the attainment of Nibbana."

etc.

Answer 1

They are his own reflections as far as I can tell. IMO the suttas don't suggest that the 4 brahma vihāras keep each other in check. My interpretation is that each of the 4bv on its own, like every other major pre Buddhist concept that the Buddha borrowed and then redefined, like the 5 faculties, 'dukkha', 'arahant', becomes subservient and must conform to the Buddha's teaching on 4 noble truths, and right view especially. So the upekkha as a brahma-vihāra, essentially becomes the same upekkha of 4th jhāna. Whereas upekkha pre-Buddhist, would probably mean one has the equanimous observation of someone with the understanding of karma, rebirth, but obviously not the full understanding of a Buddha and an Arahant that ends rebirth.