Let us begin with the familiar view that life has a meaning only insofar as we make it meaningful in the way that we live. This is to focus on the value of each individual life, in which respect it may be contrasted with human destiny as being part of a greater scheme of things, as when we look to religion to give significance to our lives beyond our earthly pursuits. What is implied, then, is that human life is devoid of any transcendent meaning, so that we are not the protagonists in a cosmic drama starring Christian or other deities, the final act being that in which we depart this life and set sail for another. On the contrary, when we die we sink into oblivion, and that is all there is to it.

If, as humanists, we argue that life is what we make it, then we have to reconcile this thesis with the facts of mortality, misery and change, and here our adherence to the argument is at the mercy of storm and shipwreck, the sun always rising over an uncertain sea. When we are bereaved, or when at the end of our own life we struggle desperately to stay afloat, then it may be hard not to feel, as a symptom of powerlessness, that life has no point and that self-deception and transience are the only constants in this world. We say when a loved one dies that only last week she was making plans and full of hope, which has now been so cruelly dashed, and that it reminds us once again that we are as nothing in this universe, there being no other, or that nothing exists except by accident and happenstance.

It is hard to decipher the subtext to such reasoning, except that it clearly includes the idea that mortality and suffering detract from the meaning of life. And yet, one can imagine an individual who lives for ever, despite which he is troubled in the same way as the rest of us by the possibility that his actions are ultimately pointless. If his longevity is such that the narrative of his life unfolds on historical timescales, his childhood being as distant as the Stone Age and beyond, though still vividly recalled, then this may affect his sense of what is real and important. Perhaps a feeling of emptiness, of events having the reality leached out of them by the flow of time, would be more acute in him than in mere mortals with their thin biographies, and with their delusions of stability more or less intact. And, of course, he could look forward to more misery than is in store for other people – in fact, to an eternity of suffering, not to mention the boredom of never doing anything new, the high point of each day being the change of date.

If this is what the passage into an endless future would be like, then it shows that immortality does not guarantee meaningfulness, or not if one's life continues on the same course in every other way. But suppose that in addition to immortality, or even instead of it, human life underwent significant change, such as to revolutionise the view we have of our place in the cosmos. It could be, for instance, that the gods vouchsafed to us compelling evidence of their existence, or that scientific discoveries, whilst falling short of religious revelation, nevertheless satisfied the same need in us for meaning and transcendence. It is, after all, a familiar refrain among exobiologists that if extraterrestrial life, be it ever so humble, were to be discovered, then it would have a transformative effect on human consciousness. This, it has to be said, is clearly untrue as it stands, for it is unlikely that the harassed parent or the professional hit man, the stooped peasant or the porn star, would be transported into a higher realm of being by the discovery of a Martian worm.

Suppose, however, that we learnt of the existence not of alien invertebrates but of advanced civilisations, the emissaries of which presented themselves to us here on Earth as saviours of our planet, bearing reasonably priced climate stabilising tools, or as ambassadors from the Milky Way Confederation of Developed Worlds, united against the forces of darkness lurking in the Andromeda galaxy. Or, again in the realm of science fiction, think of the film ‘Close Encounters of the Third Kind’, with its quasi-religious theme of a visitation in the form of a musical mother ship, one which bathes in a celestial light the chosen few who are about to ascend into its bosom. Imagining such events, we may easily come to believe that contact with an alien intelligence protective of the human race would elevate its status as it stepped from planet to star; but what we now have to ask is whether this is to imply that our lives would acquire meaning in a deeper sense.

It would, after all, be a small step compared with that which the devout Christian expects to take from this life to the hereafter; and yet, such people tend to drink from the same well of unhappiness as those without faith. That said, some among them achieve serenity in this world, which they regard as a proving ground for entry into a realm of eternal bliss and ultimate meaning. Of course, the non-believer need not agree that secular life is devoid of meaning, if that is implied, or that human life on Earth is valid only as a means to a supernatural end. It seems to be generally assumed, however, that the Christian hereafter is quintessentially meaningful, so let us now ask what the idea of heaven can tell us about the concept of the meaning of life.

If we think of heaven as representing the ultimate in eternal bliss, then by that definition it is free from suffering, as also from the annoyances and frustrations which reduce us to the level of horses tormented by flies. It is regarded, indeed, as a higher state of spiritual being from which not only insects but also all forms of negativity are absent, no ripples of envy or malice being allowed to ruffle that oceanic feeling of being at one with the Almighty. What must be absent, too, or so it is assumed, is any feeling of doubt about the meaning of life, since God in his immanence is in all things. Clearly, this numinous quality of the divine landscape is one that the architects of Christianity strive to capture in stone and stained glass and in its rituals of worship, whether those of the parishioner in a quiet church or the congregant whose voice resonates to the sound of the organ in a grand cathedral. The feelings thus induced are informed by the story of Christ, but when lacking that structure they may occur quite separately from any religious narrative, as when evoked by meditation or recreational drugs or by dancing to the point of frenzy.

In my own case, for instance, I would fast and dance in order to wake my senses to the world, and I vividly recall a clear summer night on a remote beach in the Gower peninsula. The full moon in a sparkling sky shone a silver swathe of light on the sea, and at the water's edge a sighing sound as the long fingers of the surf caressed the swell of sand. Touched by beauty, we desired its exalted embrace, and we gyrated ever faster around a driftwood fire until abruptly the music stopped. And when the giddy whirl of flames and shadows came to rest, my eyes opened on sky and sea transformed. The moon's reflection on the sea was now the glowing wake of unseen space-bound ships; and beyond Earth's edge the black ocean of the interstellar void; and on its far shore the glittering cities of the Milky Way. Enraptured, I opened my arms to the diamantine stillness of the sky, immensity of yearning measured by infinitude of space. And for a moment, touched by eternity, the ego to which I was in thrall relented, self and its objects melding into the one consciousness, and within it a cathedral dome of stars, the only sound the ebb and flow of sighing at the fingertips of the tides.

A characteristic feature of such elevated conscious states is that events unfold without, as it were, a backward glance, no regret being felt as one experience yields to the next. Like a child I delighted in the wonders I beheld, and I clutched at the fingers of the present as my eyes brightened with stars, my gaze voyaging beyond them to the myriad constellations of the galactic disc, which for exquisite moments filled my world. There is, indeed, a childlike quality to being thus enthralled, and in the same way, if less magically, Christian believers place their hand in God's on the steps of cathedral or church. Such comparisons may help us to conjure up eternal bliss, even if earthly delights are always limited in duration, in view of which it helps, too, if we are able to imagine these experiences of the sublime as being indefinitely prolonged, which in my case would have meant that I continued to inhabit that magical universe of light and space.

The point, anyway, is that parts of the wealth of human experience may be used as capital for conceiving of eternal bliss, which we may picture not as a constant state but as variations on a blissful theme, much as we pursue different sources of fulfilment here on earth. Speaking of capital, the return will be even greater if, as I now suggest, we relax the requirement of perfection and allow into heaven the kind of flawed happiness with which we are all familiar, as when eating ice cream when plagued by flies, or when dancing frenziedly but never quite breaking the bonds of self.

Let us now consider the following objection to this approach, namely that however closely we assimilate heavenly bliss to the best that human life has to offer, the fact remains that the idea of a hereafter is incoherent, for to be alive is to be corporeal in a physical world, and it is part of Christian doctrine that the soul, not the body, ascends to heaven, which is not a physical place but a state of being. To this it may be replied that although the objection seems valid, it leaves open the possibility that heaven exists in a form that is immune to it. Perhaps when we sink into what seems to be the oblivion of death we surface in a different body on a parallel planet, one in which God reveals his presence and bathes us in the warm glow of his beneficence, so that we know that we are in heaven, even if the way in which it was depicted in scripture turns out to be incorrect. Such a world seems conceivable, provided we do not interrogate it too closely, just as I portrayed with very wide strokes of the brush an individual who is immortal here on earth. It could not be a perfect world, since it occupies a physical realm, but we have just seen that perfection may be dispensed with.

That being the case, and given that this imaginative exercise serves a purpose, which is to elucidate the concept of the meaning of life, we may now ask whether such meaning is necessarily realised in heaven. If certain objective conditions must obtain before heaven may be said to exist, then it would seem that the link with particular states of mind, namely blissful ones, is causal, so that it could be different. Perhaps in some cases a newcomer to heaven is initially very happy until doubt begins to intrude, so that eventually she comes to believe that heavenly pursuits are pointless and that her life on earth had more meaning. Such a belief is heretical, but the concept of the meaning of life straddles fact and value, so that she cannot be accused of misapplying it by rejecting a particular view of what it consists in. This, it seems to me, is a pivotal point, for it undermines the mystique of heaven as the crucible of all meaningfulness, the atheist having to be content with her life being what she makes of it. It is true that if there is a heaven then God is in it, but in principle our newcomer could fail to be impressed even by him, especially in view of his appalling human rights record, and it is imaginable, indeed, that hell is populated by disillusioned Christians who have had enough of heaven.

If we resist the temptation to speculate further on the demographics of the hereafter, then there remains little to be said about the notion that once we have passed through the gates of heaven the question of life's meaning is settled. Clearly it is not, even given the fact that heaven is by definition for ever, whereas on earth one has only a short-term lease. As before, then, we may ask whether a finite human life can have meaning, one response to which is to point out that people vary in their attitude to death, which some of them seem able to accept with equanimity. The fact remains, however, that the fear of death weighs heavily on the bones of many of us, the pressure not being eased when we are told, as is often the case, that our fear is not of death itself but of dying. I would say, on the contrary, that the mortal enemy we dread is non-existence, our own and that of our loved ones, and I imagine a returning time-traveller showing me footage from a hundred years into the future. Here is my house, and gazing through the windows I see only strangers, for I am dead and long forgotten. Here are the clubs and discos of Cardiff, the dance floors crowded with other people but empty of me, always and for ever. And here, finally, is the cemetery and my sunken grave, the headstone listing, my ship having foundered on the rock of old age or accident.

Where, then, does this leave us? One answer, in view of the earlier remark about fact and value, is that we are free to decide whether or not the spectre of death renders human life meaningless. For myself, however, I am not so much free as engaged in a struggle, one which perhaps this act of writing will help to resolve. I have no doubt but that I would love to play a central role in the Ultimate Cosmic Scheme, and would wish above all else to be a god, so that I could impress people with my supernatural powers. Failing that, I would settle for the kind of communion with a reality transcending misery and death which, by some accounts, is possible not only through drugs but also by listening to music and in other ways. Indeed, I am stirred and moved by, for instance, the James Horner film score from ‘Titanic’, my difficulty being not with emotion but with attaching it to thought, with forming a coherent idea of the deeper meaning which such music is claimed to unlock. That idea is always a distant speck on my cognitive horizon, one which is in peril and needing to be saved; but when in the film the iceberg plants itself in the ship's path, I behold it as an ominous marauder from a melting Greenland and Arctic Circle, even though I am aware of the anachronism, and then the music serves only to remind me of the freezing waters awaiting the passengers and the global warming afflicting us.

There are those, of course, who claim to have more insight, and they would appeal to mysticism and one's feel for what is beautiful, in this way hoping to replace or augment the consolations of religion. They believe that they intuit a hidden reality revealed by drugs or meditation, or in music and art, such that the turbulence in our lives is washed out into an ocean of stillness. In The Doors of Perception (1954), Aldous Huxley described his experience when taking mescaline, a psychedelic drug similar in its effects to magic mushrooms. His aim was to probe beneath the surface of his mind in search of spiritual enlightenment, but not having studied the book I do not know whether he succeeded. All I can say is that my own excursion into semi-mystical perceptual states, detailed earlier, was more modest in what it revealed, and it gifted me with the key not to a hidden reality but to a heightened consciousness of the beauty of sea and sky. I had no impression of cosmic doors opening as I danced, and in any case it would, as it were, have faded as the fire went out, for instance if I had believed that all change is illusory. What, after all, could this mean? If reality is timeless and unchanging, one might as well put one's hand in boiling water, since what seems to be an important effect – one's excruciating pain – is just an illusion. Not only that, but if mysticism opens a porthole onto the meaning of life, then the seascape thereby revealed must have personal significance – but why should that be the case?

Time, perhaps, to go deeper into the link between change, mortality and life being meaningless, to which end we should start not with death but with impermanence in general, some instances of which are more significant than others. When I eat an ice cream as it melts in the sun, I do not weep and say that it has gone for ever, as if it had never been, thereby relating it to the ultimate perishability of all things, for I do not feel it as a loss of that kind. On the other hand, and in a more personal vein, I vividly recall that on a stile on a footpath from Corntown, just by Ewenny Priory, I shared an ice cream with my first love one summer's day, both of us in our teens, and we gazed into each other's eyes and vowed that we would always be true. Decades later, on the anniversary of that day, I returned, the stile being the same and yet forlorn, and as I sat there I tried to reconcile my tantalising memory of her with my present awareness of an empty space beside me. It is mysterious indeed that we experience the present moment as charged with reality in the very process of its falling away into the past, to which it is connected only by remembering, which itself is a process in the same way. But also, it is arguable that memory depends on the illusion that the past continues into the present. I can speak of making that pilgrimage only because I recognised the place and its apparently enduring features, an essential framework of stability and identity in which the transient events of that lovers' tryst, gone for ever, could be located. And yet, one could argue that this is to appeal to a superficial distinction, for the stone of which the stile, the ancient priory and the village were built was no more composed of unchanging substance than were the leaves in the trees, which as I sat there seemed to look the same as on that other summer's day. This adds to the mystery, and all the more so if we note the part played by personal identity. When I sat there on my own, conflicting impressions assailed me only because I took myself and my first love to have identity through time, just as the stile and the priory seemed to be the same as before. But this should remind us of Hume on personal identity and on what it is for a village church to be the same from one year to the next.

What I suggest, then, is that such mysteries underpin the question of whether life has a deeper meaning, which we may doubt partly because of the all-pervasive nature of change and decay, some of which we feel as loss or anticipate with dread. This returns us to the subject of dying and of being dead, neither of which, in my opinion, is to be recommended, given the way in which they crash the party and upset the guests. In writing this essay, I have tried very hard to believe that life has meaning in some profound sense, however elusive and hard to grasp. At one point, when listening to the music of Mahler from the film ‘Death in Venice’, I almost succeeded, except that I noticed a butterfly in difficulties above a windowsill, and as it clawed at the empty air, an invisible instrument frantically played, I heard only the drum-roll of it landing and breaking up, a solitary figure waiting on a white beach for death, from which not even the most delicate beauty can hope for a reprieve. It is all very well to say, as people do, that the claim that life has no meaning is self-indulgent, for we would give the lie to it if we were starving or waiting to be killed. If this means that each individual is fully engaged with her life, which is charged with her needs and desires, her seeking and striving, her primal instinct to stay alive, unless she actually feels that her life is empty and of no consequence, in which case she is depressed and needs help, then I agree. But I would add that it is because one is fully alive, each moment so real, the expectation of survival intrinsic to so many of one's conscious states, that death makes a mockery of it all.

What it all means, then, is that the human race matters only to itself and that we die, these being facts that not even the humanist can face broadside on, reduced like the rest of us to keeping busy and the ship in good shape. We pretend that the world is round, but we know, really, that ahead of us the onward curve of the horizon will flatten to a final edge, the heartbeat of the engine stopped, and that the ocean and all those at sea will plunge into nothingness.

Finally, perhaps mention could be made of a local area of historical and scenic interest. On Garth Hill, a few miles to the north of Cardiff, the path connecting the main 4000-year-old Bronze Age round barrows ends abruptly at the edge of a rocky crag, which juts out above the valley of the Taff. It is a natural lookout point, in profile like the prow of a ship, conspicuous from the road when I drive to the weekly Taff's Well dance on a clear night. Peering up at it, I try to make sense of what I know to be true: that since the end of the last ice age, more than 10000 years ago, numerous human beings must have stood there, just as I have done. In my imagination, as it takes me back four millennia, I see a young couple in the heat of summer slip away from the busy construction site of the latest burial mound and follow the path leading to the crag. Poised at its edge, they gaze out across the forest, smoke drifting from the clearing by the river where they live, perhaps on the site where now I dance, and in the distance the silver strip of the sea, now the Bristol Channel, shimmering in the heat. Presently they embrace, fingers fluttering over skin, each sensation exquisite but yielding to the next until there are no more. I see them stroll away, perhaps after vowing to each other always to be true, back to where the adults of the tribe toil at the monumental task of immortalising the dead. They all help to pat the mound into place, the equivalent in geological time of making sandcastles, and then they fade from view and I continue on my way.

Each of us will one day have all that we have built of our lives swept away, for we cannot stem the tide – unless, that is, we seek salvation in the miraculous powers of a personal god. But there is no god and there is no heaven, except in the delusions of those who feel that otherwise life has no meaning. And they are right, except that, as we have seen, not even a god can guarantee that life is meaningful. Humanists, too, deceive themselves when they claim that life has the meaning we give to it, for we give it none, being much too preoccupied with all the important projects that each of us crams into it. If we look up from all this work, or if we press the off switch, we see only the blank face of the sky or the screen; and in interplanetary space there are no extraterrestrials heading our way – except in the form of asteroids with enough destructive power to shatter all our dreams. But if, instead, we lower our gaze and look around us, then we may notice the haunted looks of our fellow passengers on this voyage to nowhere, those who are adult, and the delicate space occupied at the deck rails by children, with their capacity for enchantment, and we may feel moved to respond. This, along with bathing in a cold mountain pool on a sweltering summer day, and thrilling to the cool kiss and hot caress of water and sun, is the most that one should expect of the meaning of life.