Context
In Chapter 3 of Ajahn Brahm, Dependent Origination (2002).pdf as mentioned here Dependent Origination - Ajahn Brahmali, Ajahn Brahm frames dependent origination in terms of sufficient and necessary conditions. He indicates that bhava is a sufficient condition for jāti, but Ven Sunyo (@Sunyo) has said it is a necessary condition. So which one is it in actuality?
Here’s his list of sufficient relationships, but with arrows and the necessary conditions added in bold.
A ⟹ B: A is a sufficient condition (is enough; is always a cause, but not necessarily the only possible cause) for B
A ⟸ B: A is a necessary condition (at least this is needed, something else may do the rest) for B (Yes, the reversed arrow is true, technically B is a sufficient condition for A and vice versa, so the placement from left to right is at most chronological)
avijjā ⟹ saṅkhāra
saṅkhāra ⟸ viññāṇa
viññāṇa ⟹ nāmarūpa
nāmarūpa ⟹ saḷāyatana
saḷāyatana ⟹ phassa
phassa ⟹ vedanā
vedanā ⟸ taṇhā
taṇhā ⟹ upādāna
upādāna ⟸ bhava
bhava ⟹ jāti
jāti ⟹ dukkhā
You can also represent the last link like this.
jāti ⟹ jarā-maraṇaṁ-sokaparidevadukkhadomanassupāyāsā-sambhavanti
or
jāti ⟹ jarā ⟹ maraṇa
or
jāti ⟸ maraṇa (needs aging)
In other words, if a being comes into some state of existence, does this mean they will always be born ?
Multiple Conditions
When there is a necessary condition, A ⟸ Z, it means that other condition(s) need to come together with A, then Z will happen. If B ⟸ Z, then it would be A & B ⟸ Z, but if we also add info and say that A & B together are sufficient, then A & B ⟹ Z. This would be adding more detail and explanation than before, removing ambiguity.
It can also be used to explain chronological gaps, like how birth is necessary for death, but only when there is also aging will death be sufficient. If time just froze and nothing ever changed, there’d never be death.
We can apply this to dependent origination to reveal what other conditions were needed for the necessary conditions in order to sufficiently condition the next factor. This can be used to completely describe our bhava → jāti situation.
I’ll do the other necessary conditions first as example. For vedanā ⟸ taṇhā, I believe it would need something like: avijja & vedanā ⟹ taṇhā. And you could even say vijja & vedanā ⇏ taṇhā (will not sufficiently condition). For the necessary conditions saṅkhāra ⟸ viññāṇa and upādāna ⟸ bhava, I think this will be harder since it’s more of a matter of time and change for those to happen; eventually things just have to result and have to change, and the 3 life model is to explain that.
what? + bhava ⟹ jāti
Now to apply this to our bhava → jāti situation.
Ajahn Brahm’s reasoning is this: “Also, bhava is sufficient to produce birth (see AN3.76)”
However, Ven Sunyo argues,
From AN3.76, Ajahn Brahm is suggesting bhava alone is enough for jāti: bhava ⟹ jāti.
The consciousness of sentient beings—shrouded by ignorance and fettered by craving—is established in a realm. That’s how there is rebirth into a new state of existence in the future
But, from AN4.131, Ven Sunyo is saying bhava ⟸ jāti, which mean there must be something else required, potentially identifiable.
What person hasn’t given up the lower fetters, the fetters for getting reborn, or the fetters for getting a continued existence? Sakadāgāmissa A once-returner…
What person has given up the lower fetters, but not the fetters for getting reborn, or the fetters for getting a continued existence? Uddhaṁsotassa akaniṭṭhagāmino One heading upstream, going to the Akaniṭṭha realm.
What person has given up the lower fetters and the fetters for getting reborn, but not the fetters for getting a continued existence? Antarāparinibbāyissa One extinguished between one life and the next.
What person has given up the lower fetters, the fetters for getting reborn, and the fetters for getting a continued existence? Arahato A perfected one.
But it feels like a truism. Without the thing conditioning birth, there’d obviously be no birth, so which fetters are they? I can’t find what the fetters for getting reborn and bhava are with a pāli search, so I suppose it’s the higher fetters divided in two by the differences between what they’ve given up.
The fetters for bhava must be the difference between arahant and non-returner, which is conceit, restlessness, and ignorance. This sutta has divided non-returner into two, and their difference contains the fetters for bhava. Logically, it could be desires pertaining to birth, so desire for existence, but I don’t really know.
Ignoring the lower fetters, we can derive:
fetters for bhava ⟸ bhava & fetters for getting reborn ⟹ jāti (Uddhaṁsotassa akaniṭṭhagāmino) (Desire for existence)
fetters for bhava ⟸ bhava & no fetters for getting reborn ⇏ jāti (Antarāparinibbāyissa) (No desire for existence?)
no fetters for bhava & no fetters for getting reborn ⇏ bhava ⇏ jāti (Arahato) (No desire)
or, even more reduced:
fetters for bhava ⟸ bhava
fetters for getting reborn ⟸ jāti
This sutta would have to mean that bhava ⟸ jāti, since that statement alone is vague on whether the fetters for getting reborn are there or not. There may also be a condition besides just bhava and fetters, such as needing an available body to be reborn into, or something which isn’t named, so it could potentially be “bhava & fetters for getting reborn ⟸ jāti”, but it would ultimately still point to bhava itself being just a necessary condition.
Well there’s the answer, I guess it lies in the reality of a higher non-returner not taking birth.
Actually, Ajahn Brahm’s sutta is hinting at this
The consciousness of sentient beings—shrouded by ignorance and fettered by craving—is established in a realm. That’s how there is rebirth into a new state of existence in the future.
“consciousness & ignorance & craving & bhava ⟹ jāti”
Given these texts, I must side with Ven Sunyo that bhava ⟸ jāti.
I leave this topic as a Q & A because there could be more text study which changes this.
What about me, too?
As an explanation for vedanā ⟸ taṇhā, Ajahn Brahm said
vedanā is not a sufficient condition for taṇha. Vedana are certainly experienced by arahants, but they never generate taṇha.
but he also adds
Moreover, for ordinary people, not every vedanā produces craving.
So we aren’t creating causal relationships that only apply to certain stages of enlightenment, we’re using those to make a clearer argument that these relationships either necessarily bring the next link, or may not bring it, which would generally be true for everyone, and those stages of enlightenment are just clearer examples of the lack of the other necessary conditions. So bhava not necessarily bringing birth may not just be a technicality.
This means that in the moments where a practitioner is not being fettered by the lower fetters and only by certain higher fetters, they would bhava without jāti — or dukkha. But, later, they could be pulled by sensual desire and then be born and aged and dukkha again. I can’t really put this into words that are any more relatable, but this should imply something about our own experience, probably more so for deeper meditation where said lower fetters are abrupt. For example, maybe this is why the joys of the jhānas are said to be sambodhi sukha, the happiness of enlightenment, because you would not be suffering there as much since there’s no jāti after bhava to be bringing suffering