The precautionary principle (or precautionary approach) is a broad epistemological, philosophical and legal approach to innovations with potential for causing harm when extensive scientific knowledge on the matter is lacking. It emphasizes caution, pausing and review before leaping into new innovations that may prove disastrous. Critics argue that it is vague, self-cancelling, unscientific and an obstacle to progress.
In an engineering context, the precautionary principle manifests itself as the factor of safety, discussed in detail in the monograph of Elishakoff. It was apparently suggested, in civil engineering, by Belindor in 1729. Interrelation between safety factor and reliability is extensively studied by engineers and philosophers. 
Precautionary principle - Wikipedia ↩︎