Down through the ages philosophers and poets have mused on humankind's anomalous place within the natural order. Shakespeare, in the persona of Hamlet, could see Man as both "paragon of the animals" and as the "quintessence of dust". Pascal in his Thoughts famously called us "a thinking reed", but also a 'freak', "the glory and refuse of the universe". Rilke's Duino's Elegies portrayed us as extraordinarily ill at ease in the world when compared with animals.

Whereas they remain "free from death" and are capable of living entirely in the boundless 'openness' of a perpetual present, we seem to be constantly looking back at ourselves, our eyes 'ensnaring' us instead of making us one with life.

More recently, John Gray talked of an innate imperfection, a 'flaw' encrypted into human nature that expresses itself in the way our biological needs and psychological drives interact with our reason to generate conflicting logics.

The deepening crisis of ecological sustainability, which in the long term threatens human survival on earth could well be the ultimate expression of our maladjustment as a species. Unfit for our habitat, we have evolved a unique capacity for tailoring it to our needs on a global scale and now risk destroying it in the process.

Yet the need to come to terms with the distinct possibility that the end is nigh, not metaphysically or metaphorically but literally, may provide a unique opportunity for a new form of humanism to arise founded on an ecological conception of humanity. With its feet finally on the ground such a humanism might well play a crucial role in the transformation needed to avert the possible catastrophe facing future generations.

The flaw which makes human beings both a part of and apart from nature seems to have something to do with our special consciousness, our in–built capacity for reflection and self–reflection. Whereas animals 'are', our unique capacity for self–consciousness condemns us to 'ex–ist', standing outside our lives in the very act of living them.

This has meant that, while nature has provided an inexhaustible supply of inspiration for Man's mythopoeic faculty, we have never as a species been able to be feel an integral part of the natural world except through the medium of elaborate religious or mystical cosmologies.

In the Judeo–Christian tradition this divorce from nature and discovery of mortality has been historicised in the story of the expulsion from the Garden of Eden. This act of divine punishment was made inevitable once Man had eaten of the Tree of Knowledge, now depicted as distinct from the Tree of Life.

As one commentator put it, the Biblical Eden represents "the state before the separation of consciousness from its ground, symbolised in the Garden." Equivalent 'memes' recording the loss of primordial harmony with nature existed in nearly every culture before the population's fall into globalisation.

In short, ever since his involuntary expatriation from Eden, Adam — whose name popular etymology associates with the Hebrew word for the ground (Adamah) — has been ungrounded.

In a scientific age, such insights have to be translated into different, less overtly mythic discourses. For example, a neurological account of the Fall is offered by Arthur Koestler in Janus: A Summing Up.

This presents our extraordinary cognitive faculty as the product of a botched job by evolution. The extraordinarily rapid growth of the brain led to poor coordination between the limbic brain with the mesocortex and neocortex; or animal, middle and new brain. In the human sphere the logical is thus inseparable from the pathological. Faulty wiring, a defective masterboard in the three–tier biochemical supercomputer we call the human mind led to death being discovered by the intellect and simultaneously rejected by instinct and emotion.

Perhaps, then, there is a deeper significance in the official anthropological term for our stage in the evolution of the species. It is not homo sapiens, but homo sapiens sapiens, suggesting 'we know that we know'. But what do we know? Perhaps 'Man's' instinctive urge to avoid coming to terms with finitude has conditioned this comforting repetition of 'knowing', a euphemism suppressing an unmentionable truth. Homo sapiens moriens would be closer to the mark. Humans know that we shall die.

Yet in sheer survival terms our species could afford such an inbuilt propensity for elaborate denials of mortality, personal or collective, through the power of cultural symbols and ritual as long as nature remained bounteous and the resources it provided for human life were abundant.

Babylonian, Childean, Egyptian, Mayan empires lived out their metaphysical fantasies and passed into oblivion leaving little permanent damage on the ecosystem on which all human life depends completely.

The approaching point of irreversible ecological unsustainability changes all this. If human cosmologies do not become attuned to the need to preserve our terrestrial habitat, humanity will sooner or later run out of future. We are not faced by the 'end of history', but the 'end of nature', the disappearance of the particular biosphere that is the ultimate precondition for the viability not only of all existing human societies, but of any project to build a better one.

As Fay Weldon put it in her play The Hole in the Top of the World:

"We used to think that Marxism or feminism held the answers to all our problems. We thought, 'If only we can get rid of racism, change capitalism and educate people, everything will be different.' But now we know those hopes and aspirations left out something fundamental. They failed because they failed to take account of the earth we walk on. Without the earth we have nothing. Our Utopian concepts are flying out of the sky. So we have to rethink all our ideas in a new framework."

But this is surely the point in the argument where humanism should come to the rescue. Humanism supposedly provides a way of giving existence a sense of meaning and direction based on the intrinsic value of human existence, without recourse to the beguiling fantasies about higher realities or utopian visions of history which have so distorted the reality principle of traditional cultures right up to the present.

Humanism should thus be expected to play a key role in providing the ethical and ideological basis for the transition to a sustainable society, and even encourage religious traditions to produce their own form of ecological ecumenicalism.

Yet in the past humanism has always played down our dependency on our planetary habitat, placing the fulcrum of our humanity in an essentially mythological realm of spirit and reason. Aristotle's defence of slavery on the basis that less rational beings should serve the more rational indicates just how far Classical humanism was from recognising our ecological subservience to the natural world as a species. Pico della Mirandola's famous Oration on the Dignity of Man, often regarded as the manifesto of Renaissance humanism, blended Christianity with neo–Platonism to emancipate 'Man' from the Great Chain of Being, and hence from any notion of being an integral part of nature:

"Adam, we give you no fixed place to live, no form that is peculiar to you, nor any function that is yours alone. According to your desires and judgement, you will have and possess whatever place to live, whatever form, and whatever functions you yourself choose."

It would be reasonable to expect that with the rise of rationalism and secular science, humanism finally broke out its daydreaming and existentially touched base. Yet Enlightenment humanism was posited on the prospect of unending human progress unfolding on a planet of inexhaustible resources under the aegis of a 'Supreme Being' who underwrote the rational laws of nature and society, assumptions that now seem anything but rational.

Nor were successive permutations of humanism – positivist, Marxist, psychoanalytical, existentialist, postmodernist – to prove more successful in creating a solid empirical foundation for themselves in the ecological 'facts of life'. Even New Age variants of humanism, which rebelled against the mechanistic ethos of the West by exalting the wisdom of primitive cultures in their relationship with nature, have proved impotent to serve as the basis for the transition to sustainabilty. At the height of the counter–cultural revolt against 'straight society' a generation or two ago, millions could relate to Joni Mitchell's chorus in the Hippy anthem Woodstock:

"We are stardust

We are golden

And we've got to get ourselves

Back to the garden"

But this was still at bottom a metaphorical garden, an inner Eden, a man–made utopia. In this sense humanism has always been driven not by the reality principle, but by a capacity for illusion alluded to by the two tramps in Samuel Beckett's Waiting for Godot:

ESTRAGON: We always find something, eh Didi, to give us the impression we exist?

VLADIMIR (impatiently): Yes yes, we're magicians

The irony, perhaps a tragic one, is that we have been in the Garden all along and Godot has been patiently sitting there incognito in the stalls, waiting to be recognised as our most intimate friend. Throughout the many decades the European intelligentsia has been haunted by the growing spiritual crisis of the West, the basis of a genuine humanism has been staring us in the face, and pressing against the soles of our feet.

The miraculous organisation of nature and growing imbalance between it and Man as the result of industrialisation and technological imperialism was intuited long ago by Romantics such as Coleridge and Goethe.

Gradually the life sciences have revealed a level of interconnectedness and organic complexity of all terrestrial life that could only have been revealed in the most profound ecstatic state, but never known. In the last few decades ecology has grown into an advanced science that not only has developed ever greater sophistication in modelling the mechanisms of the ecosystem, but in documenting the irreparable damage being done to it by human agency.

This is a unique moment in the history of our species. Never before have we had the means to understand empirically, and not just intuitively, that we are part of the 'Web of Life' on our planet. Not dominating it like a spider or enveloped in it helplessly like a trapped fly, but made from its gossamer threads. Never before have we had at least some genuinely mathematical notions of the true vastness of the cosmos in which our planet ekes out its statistically unlikely existence.

From a humanist perspective this is thus a unique window of opportunity to heal ourselves of the compulsion to conjure up chimeras of transcendental meaning and supra–human purposes. Yet this window has been flung open at the very point when, for the first time in terrestrial history, the total impact of human life on the planet is not only causing the extinction of an unknown quantity of species, many of them yet to be recorded, but jeopardising the future of our own.

Global warming and the destruction of the rainforest are happening not in the last days of millennarian fantasy, but as empirically observable phenomena in real time. We are awaking from our cosmologies only to find that, far from being able to live happily ever after with a dream prince, the castle is disintegrating all around us.

It is a situation that outdoes any Hollywood disaster movie script in drama, surreality, and potential horror. It poses a particular dilemma for a species already predisposed to enter a state of denial about personal mortality. If we naked apes cannot face death without the protective clothing of myth, how can we contemplate the eventual extinction of our entire species without the anaesthetic of utopian projections and comforting fairy tales? The dilemma was summed up lucidly over forty years ago by the Freudian humanist Ernest Becker:

"One of the terrifying things about living in the late decades of the twentieth century is that the margins that nature has been giving to cultural fantasy are suddenly being narrowed down drastically. The consequence is that for the first time in history, man, if he is to survive, has to bring down to near zero the large fictional element in his hero–systems. This is the critical challenge of our time."

It was a similar thought that inspired the faint glimmer of hope expressed at the end of Arthur Koestler's own bleak summing up of the contemporary situation. If we were to be sufficiently gripped by a sense of urgency in the face of the growing possibility of the death of our species, then "a correct diagnosis of the condition of man, based on a new approach to the sciences of life" could just yet "lead to salvation in the nick of time".

This scientifically informed understanding of the state of emergency that humankind has entered in its relationship with its own habitat is the essence of 'ecological humanism'. 'We' (the economic, political, spiritual elites along with all those with the luxury of thinking objectively about the world) must minimalise 'our' (the dominant, hegemonic) fictions about our actual situation in order for terrestrial life to continue in any sense worthy of the term.

Clearly such a value– system is still anthropocentric. But if the human centre can finally be located in the natural world as revealed by ecological science and no longer in our mythological reconstructions of it, then the humanist utopia or 'no–place' might have the chance to become grounded and so make this earth a 'eutopia', a good place to be.