Investors and economists often use history as an unassailable guide to the future. David Frum: History helps us calibrate our expectations, study where people tend to go wrong. He says investing is not a hard science; it's a group of people making imperfect decisions with limited information about things that will have a massive impact on their well-being.Frum: Experiencing specific events does not necessarily qualify you to know what will happen next based solely on what they did in the past.