1. Lang (cubobi)’s explanation is right, except for the following: “Like you said, an arahant still engages in kusala sankhara, which does not bring kamma vinnana.”
An Arahant would not generate either akusala sankhara or kusala sankhara.
– The first is obvious. The second is because an Arahant does not have any defilements to remove. “Kusala” means to “get rid of defilements.” See #11 of “Kusala and Akusala Kamma, Puñña and Pāpa Kamma”
2. To further clarify, we can take the following question from the TripleGemStudent: “If I was to connect an Arahant’s Kamma vinnana to P.S. Is that Arahants would only carry out sankhara’s (or Kamma vinnana) based on the avyakata or kusala-mula (transcendental) P.S. Is this correct?”
– An Arahant generates sankhara but NOT abhisankhara.
– Such sankhara are generated ONLY via avyakata P.S. As mentioned above, kusala-mula and akusala-mula PS do not apply to an Arahant.
3. An avyakata P.S. does not have the “avijja paccaya sankhara” step.
– Sankhara (not abhisankhara) is generated when an arammana comes to the mind via one of the six senses. That happens, for example, via “cakkhuñca paṭicca rūpe ca uppajjāti cakkhu viññāṇaṃ”
– That cakkhu vinnana is a vipaka vinnana and not a kamma vinnana.
– The relevant sankhara are those arising together with that vipaka vinnana.
– See, “Chachakka Sutta – Six Types of Vipāka Viññāna”
P.S. Another set of sankhara may arise if the Arahant speaks or take actions according to the arammana.
– For example, suppose the Arahant is asked to explain a Dhamma concept. That request comes to the mind as a vipaka vinnana through the ears (sota vinnana), which would have associated vedana and sanna; those are the automatic “mano sankhara” associated with that sota vinnana.
– Now, the Arahant will start speaking. That happens with javana citta. But those vaci sankhara are completely devoid of lobha, dosa, moha, and thus are NOT abhisankhara.
– See, “Avyākata Paṭicca Samuppāda for Vipāka Viññāṇa.”
– I wrote that post sometime back. So, let me know if it is not clear.