Like millions of other people around the world, I have been fascinated to hear five eminent speakers share with us their thoughts, hopes and fears about sustainable development, based on their own experience.
All five of those contributions have been immensely thoughtful and challenging. There have been clear differences - of opinion and of emphasis - between the speakers, but there have also been some important common themes - both implicit and explicit. One of those themes has been the suggestion that sustainable development is a matter of enlightened self-interest. Two of the speakers used this phrase, and I don't believe that the other three would dissent from it - and nor would I. Self-interest is a powerful motivating force for all of us, and if we can somehow convince ourselves that sustainable development is in all our interests then we will have taken a valuable first step towards achieving it.
But self-interest comes in many competing guises, not all of which - I fear - are likely to lead in the right direction for very long, nor to embrace the manifold needs of future generations. I am convinced we will need to dig rather deeper to find the inspiration, sense of urgency and moral purpose required to confront the hard choices which face us on the long road to sustainable development. So although it seems to have become deeply unfashionable to talk about the spiritual dimension of our existence, that is what I propose to do.
The idea that there is a sacred trust between mankind and our Creator, under which we accept a duty of stewardship for the earth, has been an important feature of most religious and spiritual thought throughout the ages. Even those whose beliefs have not included the existence of a Creator have, nevertheless, adopted a similar position on moral and ethical grounds. It is only recently that this guiding principle has become smothered by almost impenetrable layers of scientific rationalism.
I believe that if we are to achieve genuinely sustainable development we will first have to rediscover, or re-acknowledge, a sense of the sacred in our dealings with the natural world, and with each other. If literally nothing is held sacred any more - because it is considered synonymous with superstition, or in some other way "irrational" - what is there to prevent us treating our entire world as some "great laboratory of life", with potentially disastrous long-term consequences?
Fundamentally, an understanding of the sacred helps us to acknowledge that there are bounds of balance, order and harmony in the natural world which set limits to our ambitions and define the parameters of sustainable development.
In some cases, Nature's limits are well understood at the rational, scientific level. As a simple example, we know that trying to graze too many sheep on a hillside will, sooner or later, be counter-productive, for the sheep, the hillside, or both. More widely, we understand that the over-use of insecticides or antibiotics leads to problems of resistance. And we are beginning to comprehend the full, awful consequences of pumping too much carbon dioxide into the earth's atmosphere. Yet the actions being taken to halt the damage known to be caused by exceeding Nature's limits in these and other ways are insufficient to ensure a sustainable outcome.
In other areas, such as the artificial and uncontained transfer of genes between species of plants and animals, the lack of hard scientific evidence of harmful consequences is regarded, in many quarters, as sufficient reason to allow such developments to proceed. The idea of taking a precautionary approach, in this and many other potentially damaging situations, receives overwhelming public support, but still faces a degree of official opposition, as if admitting the possibility of doubt was a sign of weakness or even of a wish to halt "progress". On the contrary, I believe it to be a sign of strength and of wisdom.
It seems that when we do have scientific evidence that we are damaging our environment we aren't doing enough to put things right, and when we don't have that evidence we are prone to do nothing at all, regardless of the risks. Part of the problem is the prevailing approach that seeks to reduce the natural world, including ourselves, to the level of nothing more than a mechanical process. For whilst the natural theologians of the eighteenth and nineteenth centuries, like Thomas Morgan, referred to 'the perfect unity, order, wisdom and design' of the natural world, scientists, like Bertrand Russell, rejected this idea as rubbish. 'I think the Universe', he wrote, 'is all spots and jumps without unity and without continuity, without coherence or orderliness'. Sir Julian Huxley wrote in " Creation: a modern synthesis" that "modern science must rule out special creation or divine guidance". But why? As Professor Alan Linton of Bristol University has written - "evolution is a man-made 'theory' to explain the origin and continuance of life on this planet without reference to a Creator". It is because of our inability or refusal to accept the existence of a guiding Hand that Nature has come to be regarded as a system that can be engineered for our own convenience, or as a nuisance to be evaded and manipulated, and in which anything that happens can be "fixed" by technology and human ingenuity. Fritz Schumacher recognized the inherent dangers in this approach when he said that 'there are two sciences - the science of manipulation and the science of understanding'.
In this technology-driven age it is all too easy for us to forget that mankind is a part of Nature, and not apart from it, and that this is why we should seek to work with the grain of Nature in everything we do. For the natural world is, as the economist Herman Daly puts it, "the envelope that contains, sustains and provisions the economy" - not the other way round. So which argument do you think will win - the living world as one, or the world made up of random parts, the product of mere chance, thereby providing the justification for any kind of development?
This, to my mind, lies at the heart of what we call sustainable development. We need, therefore, to rediscover a reverence for the natural world, irrespective of its usefulness to ourselves - to become more aware, in Philip Sherrard's words, of the "relationship of interdependence, interpenetration and reciprocity between God, Man and Creation". Above all, we should show greater respect for the genius of Nature's designs - rigorously tested and refined over millions of years. This means being careful to use science to understand how Nature works - not to change what Nature is, as we do when genetic manipulation seeks to transform the process of biological evolution into something altogether different. The idea that the different parts of the natural world are connected through an intricate system of checks and balances which we disturb at our peril is all too easily dismissed as no longer relevant. So, in an age when we are told that science has all the answers, what chance is there for working with the grain of Nature?
As an example of working with the grain of Nature, I happen to believe that if a fraction of the money currently being invested in developing genetically manipulated crops were applied to understanding and improving traditional systems of agriculture, which have stood the all-important test of time, the results would be remarkable. There is already plenty of evidence of just what can be achieved through applying more knowledge and fewer chemicals to diverse cropping systems. These are genuinely sustainable methods. And they are far removed from the approaches based on monoculture which lend themselves to large-scale commercial exploitation, and which Vandana Shiva condemned so persuasively and so convincingly in her lecture.
Our most eminent scientists accept that there is still a vast amount that we don't know about our world and the life forms that inhabit it. As Sir Martin Rees, the Astronomer Royal, points out, it is complexity that makes things hard to understand, not size. In a comment which only an astronomer could make, he describes a butterfly as a more daunting intellectual challenge than the Cosmos! Others, like Rachel Carson, have eloquently reminded us that we don't know how to make a single blade of grass. And St Matthew, in his wisdom, emphasised that not even Solomon in all his glory was arrayed as the lilies of the field ....
Faced with such unknowns it is hard not to feel a sense of humility, wonder and awe about our place in the natural order. And to feel this at all stems from that inner, heartfelt reason which, sometimes despite ourselves, is telling us that we are intimately bound up in the mysteries of life and that we don't have all the answers. Perhaps, even, that we don't have to have all the answers before knowing what we should do in certain circumstances. As Blaise Pascal wrote in the seventeenth century, 'it is the heart that experiences God, not the reason'.
So do you not feel that, buried deep within each and every one of us, there is an instinctive, heart -felt awareness that provides - if we will allow it to - the most reliable guide as to whether or not our actions are really in the long-term interests of our planet and all the life it supports? This awareness, this wisdom of the heart, may be no more than a faint memory of a distant harmony, rustling like a breeze through the leaves, yet sufficient to remind us that the earth is unique and that we have a duty to care for it.
Wisdom, empathy and compassion have no place in the empirical world, yet traditional wisdoms would ask "without them are we truly human?". And it would be a good question. It was Socrates who, when asked for his definition of wisdom, gave as his conclusion, "knowing that you don't know".
In suggesting that we will need to listen rather more to the common-sense emanating from our hearts if we are to achieve sustainable development, I am not suggesting that information gained through scientific investigation is anything other than essential. Far from it. But I believe that we need to restore the balance between the heartfelt reason of instinctive wisdom and the rational insights of scientific analysis. Neither, I believe, is much use on its own. So it is only by employing both the intuitive and the rational halves of our own nature - our hearts and our minds - that we will live up to the sacred trust that has been placed in us by our Creator - or our "Sustainer", as ancient wisdom referred to the Creator.
As Gro Harlem Brundtland has reminded us, sustainable development is not just about the natural world, but about people too. This applies whether we are looking at the vast numbers who lack sufficient food or access to clean water, but also those living in poverty and without work. While there is no doubt that globalization has brought advantages, it brings dangers too. Without the humility and humanity expressed by Sir John Browne in his notion of the 'connected economy' - an economy which acknowledges the social and environmental context within which it operates - there is the risk that the poorest and the weakest will not only see very little benefit but, worse, they may find that their livelihoods and cultures have been lost.
So, if we are serious about sustainable development then we must also remember that the lessons of history are particularly relevant when we start to look further ahead. Of course, in an age when it often seems that nothing can properly be regarded as important unless it can be described as 'modern', it is highly dangerous to talk about the lessons of the past. And are those lessons ever taught or understood adequately, in an age when to pass on a body of acquired knowledge of this kind is often considered prejudicial to 'progress'?
Of course, our descendants will have scientific and technological expertise beyond our imagining, but will they have the insight or the self-control to use this wisely, having learnt both from our successes and our failures? They won't, I believe, unless there are increased efforts to develop an approach to education which balances the rational with the intuitive. Without this, truly sustainable development is doomed. It will merely become a hollow-sounding mantra that is repeated ad nauseam in order to make us all feel better. Surely, therefore, we need to look towards the creation of greater balance in the way we educate people so that the practical and intuitive wisdom of the past can be blended with the appropriate technology and knowledge of the present to produce the type of practitioner who is acutely aware of both the visible and invisible worlds that inform the entire Cosmos.
The future will need people who understand that sustainable development is not merely about a series of technical fixes, about re-designing humanity or re-engineering Nature in an extension of globalized industrialization - but about a re-connection with Nature and a profound understanding of the concepts of care that underpin long-term stewardship. Only by re-discovering the essential unity and order of the living and spiritual world - as in the case of organic agriculture or integrated medicine or in the way we build - and by bridging the destructive chasm between cynical secularism and the timelessness of traditional religion, will we avoid the dis-integration of our overall environment.
Above all, I don't want to see the day when we are rounded upon by our grandchildren and asked accusingly why we didn't listen more carefully to the wisdom of our hearts as well as to the rational analysis of our heads; why we didn't pay more attention to the preservation of bio-diversity and traditional communities or think more clearly about our role as stewards of creation. Taking a cautious approach, or achieving balance in life, is never as much fun as the alternatives, but that is what sustainable development is all about.