I have several questions, and quite probably some inadvertent presumptions. I will endeavour to try and keep them organised.
My first questions are about my understanding (and I am willing and happy to be corrected or advised).
1: Is it correct that: Lord Buddha has no interest in philosophical debate, but far more interest in the exposition of the ti-sikkhā ('three higher trainings') - the fourth noble truth (aka the noble eightfold path).
2: Is it correct that: The adhipaññā-sikkhā (wisdom training) of the ti-sikkhā is to understand and know the tilakkhaṇa (three marks of existence) thereby defeating ignorance, which in turn releases us from Taṇhā and Upādāna (grasping/clinging components of the Twelve Nidānas) that directly bind us to Samsara. That is, we must identify and eliminate the ignorance(s) of: Dukkha, Anicca, Anatta in order to be liberated from Samsara.
Now, if none of this is yet contentious, I wish to move onto the majjhimā paṭipadā - the middle way. Specifically the avoidance of two extremes in terms of understanding paññā (I am aware that 'middle way' is also used in other contexts).
3:Is it correct that: There are two extremes that one must avoid (and I am deliberately going to describe them, rather than depend upon terminology). One extreme is to disbelieve in Karma - to believe that what one does makes no difference. The second extreme is to believe that things/the self in themselves are efficacious - eg. that the self (in my tradition this is extended to all dharmas) is worthy of grasping/clinging.
4:Is it fair to identify the first extreme (a disbelief in karma) as ucchedavāda ?
5:Is it fair to identify the second extreme (a belief in the efficaciousness of self/dharmas as being worthy of grasping/clinging) as sassatavāda?
I will now use the phrase 'notion of efficacious self' to refer to a view that believes that the self/dharmas are worthy of grasping/clinging.
I now bring your attention to two translations of SN12.17
Thanissaro Bhikkhu: "The one who acts is the one who experiences [the result of the act]' amounts to the Eternalist statement"
M. O'Connell Walshe: "He who performs the act also experiences [the result]' [...] this amounts to the Eternalist theory."
My reading of these words (and this may be contentious) is that a view of an efficacious self (he who performs.. experiences) entails (amounts to) sassatavāda. In this sense, I understand that Lord Buddha is stating that the notion of an efficacious self entails a belief in some form of constancy, similar to those people who are known as the eternalists. But I believe that it is a fallacy (of affirming the consequent) to then interpret Lord Buddha as saying one must be an eternalist in order to have a notion of an efficacious self.
Certainly a belief in something's constancy will entail a belief in it's efficacy as an object of grasping - and following my reading of SN12.17 it follows that a notion of an efficacious self entails a belief in some sort of constancy, but I consider that one may still recognise anicca and yet still hold onto the self having some efficacy. In other words, along with dukkha, understanding anicca alone is not enough to free us from Samsara. We must also understand anatta in order to thoroughly free ourselves from any taint. Hence the exposition of three marks of existence rather than two.
Yet, I see many texts and expositions that consider the avoidance of 'eternalism' as being enough to remove one from Samsara. I cannot see how a belief in some sort of persistent or eternal self is required in order to continue to grasp/cling to samsara. For example, I may be fully aware that I am not the same as I was as a child, and that every part of 'me' has changed and changes from moment to moment and yet I may still, for instance, believe that fame or wealth will be worthy and efficacious causes of my happiness - or merely believe that I have some intrinsic quality that is a worthy object of my attention.
Where is the error?