The great central hope of Christianity (and other faiths) is the promise of eternal life. This is the assurance that existence does not end at human death, that we progress into another realm or dimension, this time without the encumbrance of mortality (Revelation 21 is the classic vision). The gateway to this new realm is the central event of the Christian faith, the resurrection. Christ is the firstborn from amongst the dead and where goes, we follow.
We work with a fundamental logical limitation – eternal life though is impossible to understand. It is and must be, by definition, beyond our understanding. We have never been there, and no one has ever come back with any cast iron experience to share. We can do nothing but interpret the texts, apply reason and philosophy, and react internally in our spirit. From that point “you pays your money and you takes your choice”. It lies in the domain of faith, not knowledge. Eternal life or “six feet under” are both unprovable.
Two facets of eternal life come to mind, both of which might be ascribed to the classic gospel statement in Matthew 25:46 where Jesus speaks of “eternal punishment” and “eternal life” :-
Quantity : the idea that eternal life goes on and on, for ever and ever. It’s a life outside of time and in that sense “timeless”. I do not know if it is characterised by the conscious passage of time (or the commensurate risk of becoming bored!), simply that eternal life is outside the realm that we currently see which has the arrow of time moving in one direction and with decay and entropy being its final destination.
Quality: many of the references to the bible to eternal life carry another connotation, that is, not so much how long it is, bit what it is like. Eternal life is life characterised as being subject to the kingdom of God and its principles, and eternal judgment is also that which is subject to God’s perfect justice.
Tribal views, theological strictness, and dogma about this frankly make little sense. All we have is the sacred text and what tradition has made of that text, deeply constrained by human experience and our knowledge of this life. The limitations of that lens must make us wary of describing this as “truth” ; it cannot be anything more than speculation based on our personal experience of God and a deep sense of inner assurance. As I say, “you pays your money and you takes your choice” (apparently from Punch magazine in 1848, there you are).