This is a question I’ve devoted a lot of time trying to answer. I believe it’s a question all of humanity has been trying to answer as well, with varying success. Pre-modern Hebrews / Jews did not believe in an ‘interesting’ afterlife. It was called sheol and was a dismal place where most people just sleep, awaiting the ‘world to come’ which is the true vision of Jewish eschatology, where how you existed on Earth determined your place in the world to come.
In fact most eschatological regimes hinge on how a person behaved during their Earthly life. This presents exactly the problem articulated by your question. If the only thing defining the afterlife is Earthly rules, then the afterlife must by extension be temporal.
Eastern religions created the idea of enlightenment, or liberation. You stop existing, eventually, because you have satisfied all possible wants and wishes that could ever arise in a conscious agency. It’s not a sad thing to attain but a joyous one. You’ve done everything, time to leave all this messy ‘existing’ business to the younger fellas. It was probably invented in India but soon found it’s way all over Asia.
Buddhism is the religion oriented around following an accelerated path towards enlightenment, largely through meditation. Regardless of whether your journey is accelerated or not, nobody expects you to do it in one lifetime. Absent an accelerated method, natural laws such as karma drive each individual gently, yet inexorably, towards liberation and release.
The Jewish ‘world to come’ was re-envisioned by Jesus to actually occur right here on Earth, as well as in the afterlife, as the “Kingdom of Heaven.” Jesus however was not nearly as interested in a person’s deeds, but rather the mindset behind them. He had a similar insight as the Buddha did, in that goodness and righteousness could exist even in those whose deeds could only be small.
So one could bring the Kingdom of Heaven into the Earthly realm through pure belief, which would drive one to do good things because belief fills you with the spirit of the Lord. Critically, a person’s afterlife was intimately connected to their Earthly life, just as in the Jewish world to come, just focused around the person’s inner spirit rather than outwardly acts. Jesus saw with piercing insight just how ugly and nasty Judaism had become, specifically because it had perverted God’s teachings to service the most base parts of human nature.
But this still didn’t give a satisfactory answer to the question of eternity, how does one exist in Heaven forever? How can anything on Earth, be it actions or spirit, carried over into a spiritual realm, provide for the eternal existence of the being that generated those actions or spirit? Surely the being would get bored eventually and just want to die? Would every spirit end in a poor, pathetic whimper?
To this we need to look not to Catholic theology but to a particular mystic. Catholicism mostly misses the point of Christianity for the same reason that Jesus railed against the Jewish establishment. It seeks to ensconce truth into rigid dogma. Churches are not as bad as the old Temple was, but there’s still plenty of evil hiding in those four walls. And where evil dwells, good cannot flourish.
So it’s individuals that must carry the torch of bringing God’s vision for humanity forward. There are two particular mystics whose ideas are foundational for resolving the dilemma that eternity raises.
Emmanuel Swedenborg refines Jesus’s teachings such that Christian soteriology is not based so much on belief as it is on love. Jesus’s short ministry didn’t leave room for a true fleshing out of Heaven and how it works. Swedenborg does all that work and left a veritable encyclopedia of spiritual minutiae.
You may be thinking, how do we know any of that stuff is true? Well, you don’t. Swedenborg himself didn’t really expect anyone to take him at face value. What’s important are the ideas. We can’t have direct experience of the afterlife, so in epistemological terms, justification can only be as strong as plausibility, that a frame can have internal coherence and structure. All that minutiae is very important, because it can be used to highlight holes in the Christian worldview. Sadly, it’s only really accessible if you spend a ton of time thinking and meditating on it and you have at least a half-decent grasp on the history.
Swedenborg’s ideas are so good, that they’ve been slowly suffusing the public zeitgeist in the centuries since his death. That we equate Jesus with love to the extent that we do, doesn’t really follow from scripture, we can only really arrive at it through ideas that originated with Swedenborg. Many Christians have to warn against a Christianity that is too ‘warm and fuzzy’. Jesus didn’t just talk about Heaven, He talked about Hell too. But many Christians seem to find Hell inconvenient.
Being based on love gives beings something to do after they die. Rather than just singing endless choruses with angels as is commonly believed, after death humans can busy themselves doing what they love. Hell is reframed as a relatively benign place where sprits who love evil can go so they can pursue that love for evil, away from all the ones who love good. Beings are tormented there, but it’s not God that does the tormenting, it’s the hellish beings themselves.
I promised two mystics but so far only talked about Swedenborg. The other mystic was more focused on Earth. He also sought to unify Eastern and Western traditions in order to derive a common understanding of what people are doing while they’re here on Earth. And so he came to a new insight on the eternity problem, but also on what makes people so different from each other. His name was Dr. David R. Hawkins and his work focused on this idea of a scale of consciousness.
Swedenborg did not discuss, at all, preexistence of souls. God never reveals everything in one go, but rather bits and pieces at a time. The truth is, preexistence of souls would have really heavily complicated Swedenborg’s vision and made it almost impossible to articulate given the level of scientific understanding and cultural advancement.
I consider it akin to how it took hundreds of years for Einstein to come up with special cases where Newtonian dynamics breaks down. Einstein didn’t prove Newton wrong, and neither did Hawkins of Swedenborg or Jesus. Hawkins just took the extant paradigm to the extreme, looked where it broke down, and came up with a new paradigm based on a new mystical technique to reframe spiritual existence in a way that gives additional clarity to the old ideas without committing the grave sin of throwing them out.
It bridges the gap with Eastern spirituality by giving a more clear picture of how a person slowly attains liberation / enlightenment / nirvana. Through the slow, painstaking process of consciousness growth. Humans are limited, and can only reach a certain level, after which they can no longer express themselves fully in an Earthly body.
Given Jesus’ soteriology by belief, Swedenborg’s soteriology by love, and Hawkins’ and the East’s soteriology by slow, natural growth, we can now almost fully account for human spiritual existence, and how it can occupy immense time scales. Beings move, all over Heaven, Hell, and Earth, learning and growing, for an amount of time that mere mortals can only understand as ‘forever’ even if ultimately finite.
This answer is long enough, but if there’s interest, I will continue tomorrow on my blog. I’ll leave a link to it here when it’s up. I’ll try to keep it from getting too esoteric.