Keynes was ever the optimist and changed his opinions making me value his ideas that the economy is a complex entity and people have a strong desire to make it prosper and that as conditions change, so should your theories and conclusions. Hayek was ever the pessimist arguing that the free market need not be interfered with as it will run through the ups and downs of a regular business cycle making me value his ideas that the people who are the actors in the marketplace understand the complexities of the economy and understand how to make it work