Uncertainty in the context of the precautionary principle

A paper by T. Aven in the latest Risk analysis, proposing a new classification system of uncertainties (Z is the output and X are the underlying factors influencing Z). The paper is followed by three commentaries.

In the paper the author argued that only a surprising outcome necessitates the application of precautionary principle, and the potential for surprises means we have trouble in establishing an accurate predication model (a cause-effect relationship). Dr Aven does not like the "risk, uncertainty and ignorance" system because the narrow definition of the term risk would be in conflict with common practice of risk assessment.