the study of history is that of many factors but none, perhaps, as important as cause and effect. to demonstrate this to your friend: first, rehash his memory (history) of making stupid comments about history; second, explain how this caused you to take to reddit; third, punch him in the face (effect: bloody nose). as you will be able to demonstrate, the history of your friends stupidity was a simplistic cause and that lead to the effect of your punch (connecting ideas and translating them into direct action). now the same simple logic can be applied to many things in history. nevertheless, at the end of the day, we study history to see what that were the exogenous and endogenous factors that contributed to the various causes and effects. and from those answers, we can hopefully use them to not only better understand the past, but help us in the future (maybe to prevent another bloody nose--but history likes to repeat itself because people don't really think it's important enough--so we keep on giving one another bloody noses....)