In this case, the sutta includes some ideas that are rare elsewhere. What the Pāḷi texts repeatedly show is that different ancient Buddhists thought about the same terms in different ways. Not everything that we find in a Pāḷi sutta was incorporated into Theravāda Buddhism, even in theory.
The Mahāvedalla Sutta
The Mahāvedalla Sutta is a series of questions and answers. For example, the first question asks for a definition of "faulty pañño" (duppañño; Skt duḥprajñā) and compares this with someone endowed with pañño (paññavā; Skt. prajñāvat). Note how these are not quite opposites. The natural opposite of duppañño would be supañño; while the opposite of paññavā would be apaññavā. No doubt there was a story here, but it's lost to time. It's not clear how the Mahāvedalla-kāra understood pañño, the adjectival form of paññā, but in Prajñāpāramitā it seems to connote the knowledge gained by undergoing cessation (nirodha). The series of questions continues. Define "discrimination" (viññāṇaṃ; vijñāna)? What is the difference between viññāṇaṃ and paññā? The answer here is that paññā is to be cultivated; discrimination is to be comprehended (paññā bhāvetabbā, viññāṇaṃ pariññeyyaṃ).
This explanation leaves me in the dark about the distinction, I think, because I lack the context in which to understand it. There is one other reference to cultivating paññā in Pāḷi. The Rāga Sutta (AN 6.107) describes a group of three things to be abandoned (raga, doha, moha) and three to be cultivated (asubha, mettā, and paññā) in order to eliminate them, i.e. cultivating understanding (paññā) dispels confusion (moha). This one is comprehensible on its own, but doesn't help us to distinguish paññā from viññāṇa. It seems that the Mahāvedalla-kāra did not see viññāṇa as something that could be cultivated or abandoned. But this doctrine was not developed by Buddhists and all we have is this incomplete snapshot. This happens a lot in the Pāḷi suttas.
Then the sutta asks, what is valence (vedanā) and recognition (saññā)? And are these three—saññā, paññā, vedanā—inseparable? The sutta-kāra says they are not separable because "what one experiences, that one recognises; what one recognises one discriminates" (yaṃ hāvuso, vedeti taṃ sañjānāti, yaṃ sañjānāti taṃ vijānāti MN I 293). Note that the traditional skandha meditation practice is predicated on being able to distinguish these three, while here the three are said to be impossible to distinguish individually (na ca labbhā imesaṃ dhammānaṃ vinibbhujitvā vinibbhujitvā* nānākaraṇaṃ paññāpetuṃ).
* The repetition of vinibbhujitvā here is odd, but seems to be in the original texts.
Then a change of pace. "Comrade, what can be inferred by purified mental discrimination that dismisses the five [physical] senses?" (Nissaṭṭhena hāvuso, pañcahi indriyehi parisuddhena manoviññāṇena kiṃ neyyan ti?)
* Ñāṇamoḷi & Bodhi "Friend, what can be known by the purified mind-consciousness released from the five faculties?
Interestingly, what can be inferred or understood (neyyan) from this are precisely the āyatana states. From the statement (or thought) "space has no limits" we can infer the stage of limitless space (ananto ākāso’ti ākāsānañcāyatanaṃ neyyaṃ); from "there is no limit to discrimination" we infer the stage of limitless discrimination can be inferred (anantaṃ viññāṇan ti viññāṇañcāyatanaṃ neyyaṃ); and from "there is nothing" we infer the stage of nothingness can be inferred (natthi kiñcī ti ākiñcaññāyatanaṃ neyyaṃ). And we know this phenomenon through the eye of paññā (paññācakkhunā). And what is the purpose of paññā? It is higher knowledge (abhiññatthā), exact knowledge (pariññatthā), and abandonment (pahānatthā). The latter refers to eliminating sensory experience (cf. Pahāna Sutta SN 35.24).
More questions follow on right view (sammādiṭṭhi), being (bhava), first jhāna, the five faculties, and then the section that really interests me.
Life and Heat
Life and heat are not a common topic in Pāḷi; they occur together in just three texts including the Mahāvedalla Sutta, and I will digress briefly to consider the other two. We find life and heat together in a verse at the end of the Pheṇapiṇḍūpama Sutta (SN 22.95) where death is equated with the absence of āyu, usmā, and viññāṇa (SN III 143). In the Kāmbhū Sutta (SN 41.6), which features a discussion between the patriarch* Citta and the bhikkhu Kāmbhū, we find a similar discussion of the difference between a corpse and a meditator experiencing cessation (Starting at SN IV 294). Here the bodily, verbal, and mental formations (kāya-, vācī-, and citta-saṅkhāra) cease in a meditator undergoing cessation. However, they still have life and heat, and their "faculties are serene" (indriyāni vippasannāni).
*Gahapati refers to the patriarch of an extended household or possibly an extended family within a clan structure. Standard translations like "householder" seem to miss the point.
Note the inconsistency here: a living person in both texts has life and heat, but the third factor is viññāṇa in one account and indriyāni in another. Here we might conjecture that viññāṇa is intended as the function of the indriyāni, i.e. objectification is the function of the sense faculties. We could, at a pinch, see the two terms in this context as synonyms. Though this is a neat solution, we have to consider other possibilities as well. The two texts may be trying to say something different and incompatible that we no longer understand (this is not uncommon between two Pāli texts).
I don't understand how we came to translate viññāṇa as "consciousness" but it seems plain wrong to me. Notably, viññāṇa is an action noun rather than an abstract noun, so viññāṇa and consciousness are not even on the same level of abstraction. It is my view that no Pāḷi word can be translated into English as an abstract noun "consciousness" and that our whole philosophical concept of "consciousness" is absent from ancient Buddhist dialogues (see also The 'Mind as Container' Metaphor). The use of "consciousness" in discussing ancient Buddhist discourses is a Whiggish anachronism (in which we imagine ancient Indians to be primitive precursors of ourselves).
In any case, the gist here is clear. It can be very difficult to distinguish a meditator from a corpse by the usual signs of life that we look for in a conscious and aware person, because we cannot interact with them. We could say that following cessation a person becomes completely unresponsive to the world around them. People undergoing cessation of sensory experience necessarily lack all sense of time, since all of the clues to the passing of time have, by definition, ceased. Hence, perhaps, the Buddhist insistence that the Buddhadharma is akāliko "timeless", though in a culture where death is often referred to as kālaṅkato "having done one's time", akāliko could also be a synonym for amata "deathless" (Skt. amṛta). The phenomenon of people sitting lost in samādhi for days on end is likely related to their undergoing cessation and having no sense of time passing. It is likely that thirst, i.e. a need for water, is what rouses them. Being dragged out of samādhi by thirst may explain why "thirst" (Skt. tṛṣṇa; P. taṇha) became such a key word in the Buddhist lexicon.
Life Force
Coming back to the Mahāvedalla Sutta and moving to the next section the subject is now "life" (āyu) and the "constituents of life" (āyu-saṇkhārā). The sutta explicitly states that these "constituents of life" are not phenomena that one can experience (na kho, āvuso, teva āyusaṅkhārā te vedaniyā dhammā). And then it says that, if the āyu-saṅkhārā were phenomena to be experienced, the one who experienced the cessation of awareness and experience would not emerge from their meditation, that is to say they would die. The logic here is that if āyu and āyu-saṅkhāra were part of the experienced world, then when the experienced world ceased, so too would life. Rather, the text makes the apposite observation that life continues even when all sensory experience ceases.
What did the sutta-kāra mean by āyu and āyu-saṇkhārā? It is difficult to say, because the terms are not defined. Sujato has blogged about how the words āyusaṇkhāra and jīvitasaṇkhāra are used. There is not a great deal more to be said. In the Mahāparinibbāna Sutta (DN 16) the Buddha mentions jīvitasaṅkhāra in a sense that Sujato interprets as a "will to live". He is, I think, here relying on the traditional idea that saṅkhāra means "volition" because it is explained as the six kinds of cetanā associated with the six sense spheres.
This meaning of saṅkhāra derives from the earlier Brahmanical use of the Sanskrit equivalent. In Vedic ritual, a saṃskāra is a rite of passage. When performing these rites, the Brahmin priests carry out a series of actions (karman). Hence, in Buddhist usage, saṇkhāra/saṃskāra is "an opportunity for doing karma". Keeping in mind that all intentional acts carry a karmic debt. At the same time, the unique but influential passage in AN 6.63 famously says "intention is how I talk about karma, monks" (cetanāhaṃ bhikkhave kammaṃ vadāmi). Thus an opportunity for doing karma becomes an intention to act.
Whether this meaning can be applied to āyusaṅkhāra is moot and, since Sujato doesn't make this case, we are none the wiser. He finds a way to make sense of jīvitasaṇkhāra as "the will to life" and then retrospectively relates āyusaṇkhāra to this as a kind of "vital force". In the end, however, Sujato concludes that distinction between āyusaṇkhāra and jīvitasaṇkhāra probably emerged later and that the two words are synonyms for "vitality" and "vital energies" and are best translated as "life force". This is a self-consistent explanation and it might be right. But there is presently no way to confirm such conjectures: we are trying to make sense of how a word was used in the absence of any contemporary explanation and from just a few instances that are vague and/or ambiguous. This is a common problem when dealing with older Buddhist texts (in any language).
Across the ancient world we repeatedly encounter the idea of a "life force", but it is almost always conceptualised as breath. Words indicating breath as life force include: psyche, anima, spirit, qi 氣, and prāṇa. For more on this theme see my 2014 essay: Spiritual I: The Life's Breath. In the Indian context the vital force is āṇa "breath" which itself is caused by the action of the element of wind (vāyu). Vāyu conceptualises all forms of movement. The word āyu, however, does not refer to "breath". Rather, it is related to the words aeon and age, and often refers to lifespan or longevity. Breath (āṇa) is what animates the body (kāya); the resulting animation seems to be called āyu (and is accompanied by usmā). Similarly, jīva is not related to breath but is cognate with Greek bio, Latin vivarus, and Germanic quick; all meaning "life; living".
These are not ideas that were integrated into later Buddhism. Nor does the concept of a life-force as distinct from mind and body ever become mainstream. The reason is obvious, and has also bothered European philosophers. If there were a "life-force", then it would surely have a roll to play in facilitating life after death. And if it is present in all living things, as appears to be implied, then we are in the realms of eternalism: that is to say āyu starts to sound suspiciously like ātman. Not surprisingly most Buddhist schools of thought set the idea of a "life force" outside of their orthodoxy and āyusaṅkhāra never became a mainstream Buddhists' technical term. Moreover, Buddhist knowledge of physiology never really developed beyond this Iron Age conception.
Conclusions
To answer the question in the title, a meditator and a corpse are similar in that signs of life in the form of actions of body, speech, and mind are absent. Even though the meditator is insensate, or even catatonic, they are still alive; still warm. The corpse is cold and lifeless (and decay sets in almost immediately).
Presumably, this was enough of an issue for the early Buddhists thought that it required some doctrinal explanation. That said, the terms used to explain the difference—like āyu and āyusaṅkhāra—did not seem to need an explanation in the minds of the author(s). Leaving us scratching our heads.
This sutta is not consistent with Theravāda Buddhism, if only because it unequivocally states that vedanā, saññā, and viññāṇa cannot be distinguished from each other. Nor is this statement consistent with any form of Buddhism I am familiar with. The Mahāvedella Sutta appears to be from an unknown sect of Buddhists, missing from the historical record. Their text was preserved, but the teaching lineage associated with it was not. I suspect this is true in a large number of Pāḷi suttas.
However, that āyu and usmā occur together in three texts suggests that at least some Buddhists believed in some kind of "life force" as distinct from a soul (ātman). A life force (jīva) was also important in Jain theology, where it provided the necessary continuity for rebirth. At least some Buddhists further conceptualised life as composite and posited life-constituents (āyu-saṅkhāra). However, in the end we don't know precisely what words like āyu or āyusaṅkhāra meant to those people then, because they didn't say and there is not enough context to guess.
In this case it is very tempting to smooth over the difficulty by conjecturing an answer that solves all the problems, is plausible, and self-consistent. However, this is not sufficient to establish how the author(s) thought. Any number of plausible, self-consistent answers are possible. But we have no objective facts available to help us choose between them.
~~oOo~~
