author of the widely acclaimed book "Risk"

leading edge social scientist on GM food and other environmental issues

Dr Robin Foster, Health & Safety Executive, Risk Policy Unit

senior analyst for the Government's regulatory authority on risk and safety

ex-Nuclear Inspectorate risk analyst, now leads Church of Scotland unit on technology & ethics

The debate will unravel what is really meant by the Precautionary Principle :

Is it a useful way to evaluate uncertainties where we haven't enough data yet, like climate change?

Is it, as many Americans say, an over-reaction to emotional fears about technology?

Or does it mean refraining, if we can postulate even the slightest chance of a risk?

We'll ask who bears the burden of proof before we can go ahead with a technology like GM crops?

Is it for the biotechnologist to prove a postulated risk is not significant, ;

or for the environmentalist to prove that the postulated hazard is indeed real?

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John Adams says we have a "risk thermostat" which inclines us to want a certain level of risk in our lives, so we readjust our behaviour accordingly. But we have a problem over virtual risks, like BSE or climate change where science is inconclusive, and rely more on social and personal factors.

Robin Grove-White argues that all our risk judgements are value driven. Precaution is a public reaction to the presumption that scientific ways of describing and evaluating a risk are "the facts". We need to develop a new politics of public negotiation and decision for new technologies.

Robin Foster looks at the unenviable role of the regulator, who has to decide when to err on the side of caution, and how much. Regulations and controls can reduce risks to broadly acceptable levels, but novel science often leaves a residual risk. Precaution is invoked where this could have big or irreversible consequences, even if the risk is very remote, or when societal concern is high. Yet precaution is only one factor. It must also be proportional and consistent with other risks.

Donald Bruce says risk is not a pest we should try and eliminate, but part of learning to be human - and mortal - in God's risky universe. Even precaution has its limits.