In a number of spheres, from environmental issues to public heath there is a growing tendency for the precautionary principle to be adopted in decision making. At one level, this is understandable. When faced with a clearly life-threatening situation it is better to be safe than sorry by choosing not to do something. If a grizzly bear is known to be in the vicinity then it may be wise to stay indoors until the threat has passed (or someone else has dealt with it).
However, I would argue that the use of the precautionary principle when it comes to complex risk decisions is a cop out by decision-makers. The principle is too often employed with an over-riding focus on a single issue e.g. climate change or an epidemic, and thereby over-simplifies the problem. What is neglected (intentionally or unintentionally) is the fact that every decision has consequences. The benefits of any particular course of action always incurs a cost. When it comes to risk, any decision always entails a trade-off between a cost and a benefit. The benefit has to outweigh the cost and not just marginally but there has to be a sense of proportion. In other words, the price we’re prepared to pay must be worthwhile – we don’t pay any price for a marginal increase in benefit.
The precautionary principle inherently neglects these inevitable trade-offs and the principle of gross disproportion. It also tends to be employed when there is a high degree of uncertainty over the outcome. It’s attractive in this regard because all sorts of exaggerated claims can be made about the consequences of carrying on as normal without the ability to prove or disprove them. Fear is a powerful ally.
Engineers need to do better than revert to the precautionary principle when faced with difficult and complex problems.