Friends !
I happened to visit tbf after a long time and this thread caught my attention.
Karma theory and Advaita are two topics close to my heart. Therefore, I am trying to repeat what I have attempted to say - in this forum - many times in the past, with the hope that it resonates at least with some people.
The true Karma theory, in my view, is different from the one version that is ordinarily put forward in most cases. The major difference is that there is no jīvātmā which is different from the paramātmā or parabrahman in the true Karma theory. Everything is a manifestation of the one and only brahman. We are born as a result of our past Karmas and when we die, nothing else is left (no soul, jīvātmā, ātmā or mind etc.) except the cumulative Karmas which has been created at the end of our sojourn in the present life. This cumulative Karma causes another fresh birth somewhere and that new person experiences the results of some of the cumulative Karmas. During that birth also more Karmas are added on and the cumulative Karmas make yet another birth (may not necessarily be human; it could be any living organism.) and it is in this way that the gargantuan, yet majestic samsāra is played out in this make-believe stage of this universe.
The brahman which resides within each and every living (and non-living) entity in this universe is the agent which creates the impression that there is an entire universe out there, (through the sense organs) to each one of us. On our "death" this brahman simply dissociates from the physical body which then disintegrates according to the universal law applicable to it (the body) and its numerous components.
However, our great teachers and preceptors of yore probably thought it advisable not to divulge the truth in its entirety and preferred to explain with the concepts of a certain jīvātmā which has its own unique existence, etc., may be because they thought that ordinary folks like us will not bother to improve ourselves if we were to be told that "even if you commit all atrocities in this life, it will not be you who will reap the results thereof, but someone else". But this is the simple and profound truth. For all that we claim about India being puṇyabhūmi, karmabhūmi etc., from the brahman’s point of view this entire universe itself is a projection (like a modern hologram) and there is nothing more fundamental than the karma theory which even lay people of old used to sum up in the sentence உப்பை தின்றவன் தண்ணி குடிப்பான் (uppai tiṉṟavaṉ taṇṇi kuṭippāṉ).