Hi @knotty36
Apologies if I misunderstand your question. But if it’s helpful, the distinction I assume Ven. @Sunyo was drawing is between the moment-by-moment arising and ceasing of sense experience vs. the arising of the whole potential of sense experience in general, i.e. the senses.
The latter is the meaning of ‘loka’ in this context. Even though beings experience momentary instances of sense experience that arise and cease, general experience will continue to arise in some way or another so long as the senses continue to manifest.
One basic way of distinguishing this is to think that an arahant will still experience the moment-by-moment arising and ceasing of sense experience the same as any non-arahants. When someone becomes an arahant, their senses generally wouldn’t immediately cease. So for an arahant, the general ‘world’ of sense experience is arisen, even if momentarily instances of experience are arising and ceasing.
For there to be a genuine cessation of the ‘world,’ there would have to be the permanent non-arising, non-manifestation, or non-occurrence of the world of sense experience, i.e. the senses. This is precisely what the 12 links of dependent origination are about. They describe how existence manifests from life to life, how the senses arise. Not just the momentary instances of sense experience, which is only the links of phassa and vedanā really.
It’s common for some Buddhist interpreters to say the ‘arising of the world’ refers to momentary instances of sense impression, and that ‘cessation of the world’ refers to those instances of sense impression ceasing. But this form of arising and ceasing has nothing to do with defilements; it is merely resultant (vipāka). In dependence on the sense of vision, visible forms, and visual consciousness, arises sensory contact; when those conditions disperse, the corresponding sensory contact ceases. This does not explain the root reason or origin of all of those conditions, just their momentary meeting.
So in this context, the ‘origin’ or ‘arising’ (samudaya) of the world is actually craving and other defilements. Dependent origination is meant not just to describe how passive resultants operate, but also how defilements (the active conditions, i.e. kamma) produce them. So ‘loka’ is a resultant (vipāka), and ‘samudaya’ is an active condition (i.e. kamma). Given that it is possible for sensory contact to occur even if there is no craving—such as in arahants—then ‘the world’ here must mean the senses arisen from craving, not just individual occurrences of sense experience. If that helps!
In terms of atthitā and natthitā, both views actually base themselves on resultants (vipāka) rather than acknowledging the corresponding active conditions that maintain and sustain those resultants. Dependent origination is supposed to demonstrate the relationship between both kamma and vipāka, because suffering (dukkha) is ultimately a vipāka. Therefore suffering cannot be removed just by removing the arisen suffering; the underlying root condition has to be addressed, which is craving.
Atthitā claims that there is an eternal or persistent resultant, such as an eternal soul or eternal immaterial reality, which is taken for granted as existing without a condition. ‘The world’ or existence / life is assumed to be self-sustaining or self-existing somehow, so ‘the cessation of the world’ is not considered possible.
Natthitā assumes that some kind of resultant (the body, or some other notion of self) simply ceases to exist at death, without acknowledging that there are conditions that sustain the manifestation of that resultant—namely, craving. So a real ‘origin of the world’ is not actually acknowledged. It’s like equating an illness with the symptoms. Although they are related, removing the symptoms does not remove the actual illness. And if the symptoms dissipate, it does not mean the illness is actually cured; symptoms will re-arise due to the underlying condition that is left unacknowledged.
So SN 12.15 must be about the relationship between defilements and resultants, not the arising and ceasing of mere resultants alone, which would not give a complete picture for someone to resolve the dichotomy of atthitā and natthitā. The Visuddhimagga actually seems like it might mention the same idea at Ch. XVII Paragraph 10 in Ñānamoli’s translation, but I’m not entirely sure what it is refuting.
Hopefully that is not too convoluted a response. 