Our body will die but not our good deeds. If nothing can erase our good deeds, does it mean everyone will become enlightened eventually?
Kamma is impermanent and has a finite duration, meaning that the kammic results of an action last only for a certain duration of time, after which it becomes exhausted.
That is why e.g. a Brahma God can be reborn as a pig in the animal realm. That happens because the kamma from the good deeds has been exhausted which in turn leads to other kamma to come to fruition.
It means also that no being will be in the Hell realms for eternity since a being can only stay there until the unwholesome kamma has been exhausted.
In my article, Escaping the Inescapable: Changes in Buddhist Karma. (Journal of Buddhist Ethics Vol. 21. 2014), I explain that karma was initially believed to be inevitable and that one had to live the consequences of one's actions no matter what. But this changed over time and various practices were developed to mitigate and eradicate evil karma. I didn't study "good" karma, but I see no reason for the same kind of reasoning to apply, i.e. good karma must be erasable in the systems of though in which the consequences of deeds are erasable.
One of the perennial problems for Buddhists is that, for the unenlightened, there is a vast predominance of craving and aversion, due to ignorance. Buddhists swing between enlightenment as transcendental (and therefore more or less unobtainable) and immanent in all beings (and therefore inevitable). The trouble is an immanent model is that it devalues the idea of enlightenment if everyone can get there, and will get there more or less with no effort. The trouble with transcendent models is no one is motivated by the unobtainable for long. Both extremes demotivate people and if on looks at Buddhist history we can see periods of stagnation when one or other model is unchallenged.
As part of this process. earlier models seem to get forgotten or repudiated and new ideas such as "interdependence" or "buddha-nature" get invented to fill the gap.
Many people think that Buddhism will inevitably mean that everyone will get enlightened. Mahāyāna Buddhism makes a big deal of the idea of "saving all being from suffering." Which suggests that they think such a thing is possible (despite the evidence of 2500 year of Buddhism). On the other hand saṃsāra (the cycle of death and rebirth) is usually portrayed in Mainstream Early Buddhist texts as beginningless and endless. Liberation is not found in saṃsāra, but by leaving it behind through ending rebirth. In this case we could have no expectation of everyone getting enlightened because that would mean the end of saṃsāra - a logical inconsistency.
A standard way of looking at karma is that none of our deeds "die" when our body dies. They are the condition which determines our next rebirth which will, in the more general way, reflect the life we have lived, for better or worse. But all deeds come to fruition at some point. Good deeds have to have a time limit also, else they would be permanent, and it is axiomatic in Buddhism that all things are impermanent.
Nāgārjuna spotted a little problem with this standard view however (Mūlamadhyamakakārikā Chp 17). It is this: dependent arising specifies that when a condition ceases, the effect for which it is a condition also ceases. Thus there is a problem with karma because it requires that effects manifest a very long time after the condition has ceased. Again Buddhists proposed many solutions to this problem, but none of them actually solve the problem. The arguments are quite complex, but I tried to summarise them in an essay called The Logic of Karma. Unfortunately my conclusion is that the internal logic of all the existing explanations for karma are internally inconsistent. Nāgārjuna's answer was to argue that actions, agents, consequences, etc are all just illusions, which is not very satisfying.
What will erase our good deeds?
When the karma for that action bears fruits, that "good deed" will "erase" so to speak.
- The fruit that is borne from this good deed creates new situations and karma, good and bad. Thus, "that" good deed will never stop producing and in itself probably came from some other karma ad nauseum..
- According to the section about "regret" (one of the 10 root afflictions) in "How to Measure and Deepen Your Spiritual Realization": if you have strong regret/doubt about a good action that you did, then it will diminish the good karma for that action. For example, if you saw a beggar on the street and you gave them all your change and felt great about it: great. But if after, you start regretting and second-guessing it... the "good karma" for that will nearly away. The same principle can be said for "bad karma."
If nothing can erase our good deeds, does it mean everyone will become enlightened eventually?
- No karma is permanent, good or bad.
- Karma is not associated with enlightenment: the worst person can still technically attain Awakening because it is a non-dual penetration beyond good or bad. That being said, even though Enlightenment comes from reasons beyond conditions and environment and karma.. of course Enlightenment is still easier to attain with a propitious environment.