The precautionary principle seems to have been first used as an explicit concept in 1980, and has not ceased developing since then. It received public recognition at the Environmental Conference in Rio in 1992, and was included later that year in the Treaty of Maastricht. In the intervening years, it has transcended environmental issues to include food and health concerns. The precautionary principle has sparked off many heated discussions within the World Trade Organisation. The term is so frequently repeated in most spheres of public life that it has become something of a mantra. And yet it remains controversial and has been given many different, and often contradictory, interpretations by its supporters and opponents. For these reasons, the author argues that it is essential to clarify the way the term is used. He explains that he has tried to give the reader 'the basics of what I believe each citizen should know and understand about the precautionary principle so that he or she may participate actively and usefully in a constructive democratic debate. It is important that we provide the precautionary principle with positive content ' i.e. that we make sure the term and its applications are defined in such a way that it can be understood and used by all. Such clarification will enable it to become a tool of social progress rather than a handicap or source of conflict.'

Philippe Kourilsky is the head of the Institut Pasteur and a member of the French Academy of Science. He teaches at the Collège de France and is the author of Artisans de l'hérédité and La Science en partage.