To decline/ reject Christianity is to render Life futile

If it is correct to say, as I do, that this mortal life was created for a reason; then if that reason is rejected, it must tend to render our life futile.

So, there is a choice. We are not compelled, but need actively to choose the post-mortal Heavenly and eternal life that Jesus made possible for us. And since that is a positive choice, it is not-irrational to reject Heaven.

Yet to live in a world, to live a life, that is Designed for our personal education aimed at Heaven; yet to decline the offer of Heaven, does mean that our mortal life has been pointless, in an ultimate sense.

It would be like spending one's entire life at medical school while determined never to become a doctor. To train as a marathon runner for decades, yet never run a marathon. To practise scales and arpeggios on the piano, yet never play a tune.

That is, indeed, the situation for the billions of people who now live and have-lived mortal lives; while declining to accept the gift of Jesus.

If such people are theists, they will (I think) move on to something much like their religions describe - Nirvana, paradise, unconsciousness...

(If they have mistaken the purpose of this world, their lives will be structured according to that mistake. As if they were actually at medical school, but believed they were being trained as a lawyer....)

But mortal incarnated life on earth - This Life - is not a necessary experience for the attainment of any of these not-Christian religious objectives.

Non-Christian religious might as well have gone straight to that state, without living-through this Life. Entering Nirvana, or paradise, does not require a prior mortal life - you might as well be born there.

If you do Not want to become a doctor, it is pointless to spend your life at medical school - training for a profession you have no intention ever of practising.

(This is what I mean about this Life being futile if Jesus's gift is rejected.)

As for those who are atheists, those who deny that this World was created and deny it has a purpose... they are objectively insane. Incoherently delusional; with disorganised thinking and a purely subjective understanding of reality; because without creation all meaning is personal and arbitrary: That is all that is possible, That has been chosen.

Atheists are at medical school, but deny the reality, even the possibility, of becoming a doctor. Their lives are not just futile but crazy, since they necessarily, by assumption, experience all educational experience as arbitrary torment or random pleasure.