Someone asked, referencing Luang Pu's manual for abbots, about the two kinds of nibbana he described — sa-upadisesa-nibbana ("living nibbana") and an-upadisesa-nibbana ("dead nibbana") — how they differ, and whether living nibbana is nested within dead nibbana.

Living Nibbana: Reaching the Nibbana Element While Still Alive

Living nibbana is when, while still abiding within the five aggregates at the center of the Dhamma body, one has reached nibbana. The nibbana element appears after fully purifying the mental defilements (asava) and attaining arahantship — reaching the nibbana element that resides at the center of the arahant's Dhamma body. Yet one still remains in the human world, still relying on the five aggregates to carry out one's duties and benefit beings. One abides in this nibbana element within the arahant body — this is what's called living nibbana: still alive, not yet passed away, sustained by the five aggregates just as anyone else is, except abiding at the center of the nibbana element within the Dhamma body.

Dead Nibbana: Complete Release from the Five Aggregates

Dead nibbana means passing away — the dissolution of the five aggregates from the human body. This requires the cultivation of the sacred knowledge (vijja) needed to enter nibbana, shedding the five aggregates entirely and entering the nibbana realm, freed from the pull of the three realms of existence, freed from the cycle of birth and death. This, too, depends on cultivating that knowledge after all defilements have been purified — when the moment comes to release the aggregates and be fully freed from them.

Is Living Nibbana Nested Within Dead Nibbana?

Living nibbana resides at the center of the Dhamma body of one who has attained arahantship. Once all mental defilements are purified, the nibbana element appears within the arahant's Dhamma body. A person who has purified all defilements dwells in the state of living nibbana while still alive. But for someone who has not yet attained this — who has not yet eliminated all defilements — the arahant-level Dhamma body still exists (as part of the eighteen bodies along the lineage of elements and dhamma), but the nibbana element has not yet appeared, because the defilements have not yet been fully purified. Only once they are purified does the nibbana element appear within the arahant Dhamma body.

As for entering the nibbana realm itself — one can do so much as, while still human, having reached the sphere of dhamma, one can travel to the subtle human body, the celestial body, or the brahma body and perceive that they truly exist, visiting them, so to speak — but one cannot remain there permanently; one must return to the human body until the aggregates are finally released. It is the same for an arahant: they can enter the nibbana realm, but cannot remain there permanently until they are truly and fully freed from the five aggregates.

Dead nibbana, then, refers to the nibbana realm itself — the Dhamma body that comes to reside within the nibbana realm is called "the Buddha in nibbana"; the realm is the abode in which that Buddha resides. Only once fully freed from the five aggregates can one enter and reside there permanently. Living nibbana, by contrast, does not require giving up the aggregates — it already exists at the center of the arahant Dhamma body. For it to arise, one must cultivate the sacred knowledge until fully freed from all mental defilements — meaning the systems of unwholesome and neutral-indifferent dhamma can no longer draw one in at all. Once freed from both of those systems, one abides purely and entirely within the wholesome system, and noble nibbana appears at the center of the arahant body in this sense. One then abides within this pure and complete nibbana element, untouched in any way by the unwholesome or neutral-indifferent forces. This is living nibbana — freedom from the systems of neutral-indifference and unwholesomeness while still alive, sustained by the five aggregates.