There are several possible answers to the question posed by my title. ‘Around tea time on Wednesday, July 19^th, 3072’, for example. Or ‘Just as you are sitting down to a candlelit dinner with the one for whom you have nurtured a secret passion for thirty years’. If your luck is running at a really low ebb, it may happen half a minute after the prison warders have strapped you to the gurney and flooded your body with electricity, or, less depressingly, while the bullet is still an inch or so from penetrating your lung.

There are, to be sure, less frivolous responses. ‘No time at all’, for example. Like climate change, the Second Coming is happening all the time, striking into this world at every moment in scorn of its twisted priorities. It is hiding in plain sight, inscribed in every word and gesture, so pervasively present as to be effectively invisible. A slight tilt of perspective would be enough to reveal it. One thinks of the Jewish tradition for which when the Messiah arrives he will transform the world by making a few minor adjustments. Donald Rumsfeld's legendary classification of known knowns, known unknowns and unknown unknowns, the only contribution he ever made to the edification of the human race, passes over a fourth possibility, namely unknown knowns, things which we know but don't know we know. A good deal of ideology falls into this category, and so perhaps does the Second Coming. To know it is to realise that we were knowing it all along. Freud, one need hardly add, would scarcely have found such a paradox surprising. On this view, the coming of the kingdom might be seen as the historical unconscious, which like the individual unconscious is separated from the ego by only the thinnest of membranes but which for most of the time is nonetheless opaque and enigmatic. Only in special moments such as dreams and visions does the unconscious break out in all its sublimity.

Yet it would seem that the unconcealment of this dimension, rather like what philosophers call the dawning of an aspect, must itself occur at a moment of time. Is this true? Or does the death of history, like the death of an individual, drop off the temporal scale altogether? Is it as futile as asking what time it is on the sun, to borrow a remark from Ludwig Wittgenstein? If it is, then it resembles the Creation in this respect, which could not have taken place in time because it is the origin of time itself. Wittgenstein remarks in the Tractatus that death isn't an experience in life but the limit of that experience. One can be present at one's own dying, but not at one's own death. If it happens at a particular moment in time for those gathered around the deathbed, it happens at no identifiable moment for you, since if you could register that moment you would still be alive. As far as you are concerned, your last moment isn't the moment of your death, but the moment before that. One is reminded of a snatch of dialogue in Waiting for Godot: ‘What's the last thing you remember?’ ‘I've forgotten’. ‘No, I mean the thing before that’. Yet since most people can't predict at exactly which moment they will die, neither can they recognise the moment before it as their last. I say ‘most people’ because there are rare cases in which you can know for sure that you will die in three seconds from now – in which case you would know what your last moment will be for others, though not for yourself.

Perhaps what applies to individual deaths also applies to the end of history. This would only be true, however, if the end of history was a matter of death rather than transformation. Since it involves the latter, any complete analogy with an individual's death breaks down. The transformation of everything can't be modelled on the transformation of something in particular, any more than the loss of the self can be modelled on the loss of one's car keys. Yet there may be some sense in which it can be experienced all the same, which is to say that the passage from time to eternity happens in time, or at least is initiated there. If not, it is hard to see how it is time which is transfigured, along with the material bodies we have now. Being events in time is also presumably true of the Incarnation and Resurrection. The intersection of time and eternity cannot involve the abolition of the former, but rather the realisation of its deepest significance. From a human viewpoint, Jesus cannot have been conceived a-temporally, and the same is true of his being raised from the dead. We don't know precisely when this was, and we couldn't have taken a photograph of the event had we been lurking around his tomb with a mobile phone; but we know that he didn't rise from the dead five minutes after his execution, or five hundred years later.

In a similar way, the usual answer to the question posed in my title – ‘We don't know’ – is true if one is inquiring after the exact minute, but not if one is content with a rougher sort of reply. ‘We don't know’, in short, can be improved on. In fact, the Gospel tells us when the kingdom will arrive, namely as a thief in the night. This isn't of course to be taken literally, but neither should it be seen as purely metaphorical. Or rather, we should exchange one metaphor for another and equate ‘night’ with ‘dark’, ‘gloom’, ‘confusion’ and so on. Christ, that is to say, won't arrive in the clear light of humanity's most impressive attempts at building the New Jerusalem. On the contrary, he is only likely to rejoin us when we are in the worst possible shape. We have of course been in pretty bad shape ever since we emerged on the earth; but there are degrees of depravity even so, and our current condition is fairly high on the scale. An astronomer once remarked that if we were ever to explore other galaxies, we would discover four kinds of planet: those which were uninhabited or uninhabitable; those which were home to a species which had not yet discovered nuclear power; those which housed creatures who had discovered it but had successfully defused its destructive potential; and an enormous number of radioactive planets.

Every age has had its clutch of apocalyptic doomsters, but all that changed just over a century ago. It was then that the human race showed such lurid visions to be simple realism by developing the ability to wipe itself out. Since then, it has begun to realise that it has been busy wiping out much of its own habitat for some time. Most apocalyptic thought imagines that the catastrophe it foresees will be visited upon humanity by some power external to it. It never seems to have occurred to most prophets of calamity that we might be clever enough to need no help whatsoever in exterminating ourselves. For the first time, then, it is possible for us to know on our pulses rather than abstractly acknowledge the dominant tone of the Gospel, which is one of urgency. Jesus warns that the end of history is at hand, and that we can be redeemed only by justice and friendship. This may not have sounded all that convincing to some of those who listened to him. It's a lot more convincing now.

Like a good many truths, then, this one becomes clearer retrospectively, as the Owl of Minerva takes flight through the darkness.(Indeed, philosophical pragmatists such as James, Peirce and Dewy thought all true propositions were of this kind). It is our dubious privilege to be able to make sense of eschatology in ways which were not previously possible. The Second Coming is most intelligible not as an arbitrary arrest of history but as an act of mercy in circumstances which cry out for it. An occurrence which winds up history must make some historical sense. Unlike Donald Rumsfeld, God is for the most part a non-interventionist. What few irruptions into history can so far be laid at his door, apart from keeping the whole show on the road in the first place, are not of course simply historical events, but acts of love. It would not be conceivable for God to act otherwise, any more than an angel could play roulette. It is reasonable, then, to believe that only when we are in truly desperate straits will God stretch out his arm for a final time.

Yet since God respects our freedom, being the source of it himself, he will presumably give us every opportunity to build as much of the New Jerusalem as possible with our own hands. Only when it is clear that this project lies utterly in ruins is he likely to act. And whether we have failed or not is to be judged not simply by the state at which we finally arrive, but also by every historical struggle for justice and friendship weighed against every squalid betrayal of it. In this sense, then, the coming of Christ has not been deferred. It would seem so, to be sure, for those men and women of the early church for whom the only history conceivable was salvation history. For them, and perhaps for Jesus himself, one had simply to stand surrendered in faith to the Messiah who was imminently to return. But that return involves free human agency, not simply the faith that history is even now washed up had we but eyes to see it.

None of this is to suggest that we shall prove unable to prevent climate disaster or dispense with weapons of mass destruction. The ingenuity which allowed us to violate Nature and manufacture chemical weapons in the first place can always be turned against such projects. The apocalypse, let us hope, may not turn out to be this particular conflagration at all. Indeed, there is apparently no end to the number of catastrophes which humanity is capable of inventing. So it's fine to go ahead with that candlelit dinner. Just don't linger too long over the dessert…