The Precautionary Principle

(with Application to the Genetic Modification of Organisms)

By: Nassim Nicholas Taleb, Rupert Read, Raphael Douady, Joseph Norman, Yaneer Bar-Yam


Date: 17 October 2014

Key Concepts:

  • Precautionary principle: preventing decision makers from putting society as a whole at risk .
    • Potential global, irreversible implications (fat tail, systemic, risk of ruin).
    • Action should not be taken in the absence of near-certainty about safety.
  • Proper consideration of risk involves assessing probabilities and consequences.
  • Probability distributions: thin versus fat tails.
    • Mild variations.
      • Bottom-up, slow evolution (nature).
      • No individual variation represents large share of sum of population.
      • Limited consequences: independent, local impact.
      • Example: people’s weight (no human is heavier than 10 x average).
      • Harm comes from collective effect of many events.
    • Large variations.
      • Top-down, engineered (man-made, some in nature).
      • Single deviation may take up large share of sum of population.
      • Large consequences: interdependent, cascading, systemic impact.
      • Example: people’s net wealth (single person > 10 x average).
      • Harm comes from the single largest effect.
  • Consequences: local versus systemic risks, risk of ruin, fragility.
    • Local versus systemic.
      • Localized, non-spreading impact.
      • Connected, propagating impact.
    • Risk or ruin: non-zero probability of an unrecoverable loss.
      • Low probability wrongly interpreted as acceptable risk on one-off basis.
      • However, over time, as exposure increases, probability of ruin increases.
      • Implication: future ceases to exist = cost is effectively infinite.
      • Traditional risk assessment of cost-benefit analysis nonsensical.
      • Limited use for statistical, experimental or evidentiary analysis.
      • Lack of historic harm is unconvincing (require a very long history).
    • Fragility: harmed by uncertainty.
      • Non-linear response to random events.
      • Ability to withstand (and recover) from small impacts.
        • Large stone (weight of 10 pebbles) hurts more than 10 pebbles.
        • Converse, 10 pebbles don’t hurt as much as one large stone.
        • I’m not destroyed by cumulative effect of many small events.
        • Linked to small, local, bounded risks.
        • Allows for tinkering, progress, adjustment.
  • Real world examples:
    • Nuclear energy: PP does not apply (mostly a severe local risk).
        • GMOs: PP applies, need for severe limits.

Leave a Reply