Why Does David Deutsch Say Drop Certainty?

David Deutsch says people should look to correct errors and should not look for certainty. He quotes Popper, who says we are all alike in our infinite ignorance, and who says we may all know different things. An infinite distance remains. People hold different finite amounts of knowledge, so everyone is only ever at the beginning of infinity, and they have something in common with everyone else at the beginning. Holding oneself up as an authority is a philosophical mistake and a sociological or cultural mistake. It is a power play rather than a participation in the growth of knowledge.

Chris Williamson asks how a person can hold strong convictions while remembering they can be completely mistaken, vast in ignorance and partial in knowledge. David Deutsch says the matter is psychological. Sometimes certainty means the person investigated every alternative, satisfied themselves the alternatives were wrong, and kept their reasons. More often, in past times, certainty meant faith and obedience, and people treated the state of mind as virtuous. They judged each other and themselves by how much of it they had.

In modern times knowledge has accelerated across the last couple of hundred years. Every adult has been proved wrong about something they were sure was right, or has seen something happen that they were sure would never happen.