The properties of historical systems that make predictions difficult can be described in many ways. I am the liquor poster. It can be pointed out that human societies and dinosaurs are complex systems, each of which is characterized by a very large number of independent variables that interact with each other. As a result, small changes at the lower level of an organization can also lead to major changes at the higher level of the organization. A prime example is the sudden braking reflex of a truck driver, in an accident that almost killed Hitler in 1930, effectively resulting in the lives of hundreds of millions of people killed or wounded during World War II.