"You're at a party and you're tapped on the shoulder and told you have to leave. The party is still going on but it's going on without you. And even people who swear to remember you are not really going to do so."

Nevertheless, for Christopher - and I suspect for many - the prospect of heaven sounds even more frightening.

"You get tapped on the shoulder, but guess what? The party's going on forever; you have to stay. And not only that, but you have to have a good time - the boss says so." (He shudders.) "Anything eternal is probably intolerable."

I sympathise with the shudder. As a child, I would sometimes lie awake with eyes like full moons, horrified by the blankness of eternity: vast, unending, unavoidable. There would never be any hiding from it, no escape, not even in death. This was the type of universe in which I was trapped, and there was no other. Heaven might as well be hell; the sheer duration would eventually poison it.

But Hitchens allows himself a small loophole - "Anything eternal is probably intolerable" - and I think he's right to do so.

Is it possible that eternal things only seem intolerable to us because in this world nothing is? Might we lack a reasonable sense of what eternity will be like because we've never experienced anything that comes close? We tend to think of a single day endlessly multiplied, and soon, our mental picture of heaven resembles one of those imaginary prisons conjured up by Piranesi when he was feeling a bit peaky. Even a good party, as Hitchens rightly notes, becomes insufferable as soon as it becomes inescapable.

When we think of the eternal, we can only do so with minds and bodies that are anything but. And eternity would indeed be unbearable, if we were clothed as we are now. As Paul says, "I declare to you, brothers, that flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable." (1 Corinthians 15:50)

But that is not the eternity assured by the resurrection of Jesus. Instead, our minds and bodies will be changed, so as to be perfectly suited for the new kingdom.

The metaphor Paul uses - and this can only hint at what awaits all those who put their trust in Christ - is the transformation of a tiny seed into something altogether different. Standing under the generous, threshing branches of an oak tree, its origin as an acorn is almost unimaginable. "So will it be," says Paul, "with the resurrection of the dead":

The body that is sown is perishable, it is raised imperishable; it is sown in dishonour, it is raised in glory; it is sown in weakness, it is raised in power; it is sown a natural body, it is raised a spiritual body. (1 Corinthians 15:42-44, NIV)

The rest of the New Testament makes us wary of saying too much on the subject: "What we will be has not yet been made known." (1 John 3:2). But one thing is certain, says Paul. "We will all be changed."

Listen, I tell you a mystery: We will not all sleep, but we will all be changed - in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed. For the perishable must clothe itself with the imperishable, and the mortal with immortality. When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true: "Death has been swallowed up in victory." (1 Cor 15:51-54)

For now, the thought of eternity may be intolerable. But, in the words of C. S. Lewis, all the leaves of the New Testament are rustling with the rumour that it will not always be so.