With three simple Latin words,"Cogito, ergo sum", Rene Descartes gave birth nearly four hundred years ago to the school of philosophy that sustains the whole of modern science. "I think, therefore I am", the logical conseque-nces of which concatenate right through the extraordinary achievements of our technological civilisation, even today. It is the insistence of Cartesian thought on individual certainty, separation of mind and body, reduction into parts and rigorous analysis that has made possible so widely the conquest of the traditional scourges of humankind: deprivation, disease and death. Now we are in the process of conquering even bigger things – including the very basis of existence, space and time.
 
More, perhaps, than any other thinker, it is Descartes whose philosophy defines all that we mean by the word "modern".
 
Isn’t it ironic, then, that these same technological achievements have created a world where the underlying philosophy of living has come full circle to the very opposite of the Cartesian premise? Today, four short centuries after Descartes made his millennial breakthroughs in thought, and as an inexorable result of its own material successes, the operative premise has become "I have, therefore I am".
 
Today, for more and more of us, what we have, rather than what we think or what we are, determines our identity and defines our self-worth.
 
This is not the only irony embedded in the legacy of Descartes. The reductionism and materialism of the Cartesian method are also, directly and indirectly, at the root of many of our environmental and social breakdowns. The one-dimensional and progressively narrowing focus of scientific investigation, social action and policy making have increasingly led us away from the holistic perspective needed to manage ourselves and our resources in a sustainable manner. Hence the backlash: the growing recognition of the need to bring back multi-disciplinary, trans-sectoral, integral approaches into research, action and policy.
 
But the crowning irony of our (or, more accurately, the West’s) Cartesian heritage comes from its implicit emphasis on individual freedom at the expense of distributive justice. It is this imbalance that has brought about the socio-economic inequities, ecological threats and systemic failures that will ultimately put a cap on the limitless progress promised by the concept of "modernity".
 
Consumerism is, then, both the cause and the result of ever-accelerating production of goods and services made possible by our technological prowess. An run-away consumption, even when justified by impeccable philosophical arguments or sophisticated economic obfuscation leads nowhere, even in the relatively short term.
 
Sustainable development is simply a matter of sustainable lifestyles. It needs only two things: sustainable production systems and sustainable consumption patterns.
 
And development cannot be sustainable when it is based on either over-consumption of under-consumption. The arguments against over-consumption are now being made by a growing number of constituencies, and are well-known. To be green today means to be against today’s consumerism. Under-consumption, on the other hand, is not widely seen as such an obvious threat to sustainability. Even by the greens. It is, however, just as great a hazard to human well-being and planetary survival as over-consumption. Its impacts manifest themselves through the economics, politics and demography of deprivation, leading to their own types of social and environmental destruction.
 
The Western concept of modernity, which has brought so much to so many is now sowing the seeds of its own destruction unless it quickly tempers its societal goals and strategies to meet the needs of all and to regenerate the resource base. This means that while the rich needs to curb their appetites for products and services that destroy nature, the poor need to have more access to the things that reaffirm their place in the community and in society while regenerating the environment. Not only to have, but also to know and to think.
 
The answer takes us back to knowledge: Cogito ergo sum.