Very low probabilities

Humans are bad at dealing with very high and very low probabilities.

• Some are not computable. Bank runs can be set off by sunspots.
• The probability can only be estimated (underestimated!) from historical data.
• Pascal's mugging
• You need exponentially more evidence to get probabilities closer to 1 or 0.
• Probabilities cannot be zero or one, because then you cannot change your mind, as per Bayes' Theorem