Certainty

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts."
- Bertrand Russell, Mortals and Others (1933), often paraphrased as "The foolish are so certain and the wise are never sure."

My Positions

1. I do not believe that certainty is a position we can hold about anything.
2. The only candidate for certainty is the position proposed by René Descartes in Cogito, ergo sum: that a thinking thing exists.
3. Even the cogito should be held with some scepticism. Given how much we feel certain about and should not, it is prudent to be wary of our intuitions, even about this philosophical foundation.
4. I therefore consider myself a sceptic of the sort described by Philosophical scepticism: not one who denies that anything can be known, but one who denies that anything can be known with certainty.

Notes

• Thought experiments that illustrate the impossibility of certainty about the external world:

• Brain in a vat
• Evil demon
• The Matrix (1999)
• Plato's Cave
• Boltzmann brains

• The lack of certainty is not a practical problem. Knowledge, as I understand it, is a set of models that are sufficient to avoid surprise. A model does not need to be certain to be useful. I do not need to resolve the solipsist question before deciding whether to get out of bed.
• Certainty is also a psychological state, not an epistemic one. The feeling of being certain is produced by the brain and correlates poorly with being correct. Be wary of anyone who is certain, and be wary of yourself when you are.
• This is not a licence for false balance. That nothing is certain does not mean all claims are equally well supported (see False Balance and the Nirvana Fallacy).

Also see

• Fallibilism
• Justified True Belief
• Hard Atheism
• Münchhausen trilemma