Cormac Mccarthy said this quote

When I was in school I studied biology. I learned that in making their experiments scientists will take some group--bacteria, mice, people--and subject that group to certain conditions. They compare the results with a second group which has not been disturbed. This second group is called the control group. It is the control group which enables the scientist gauge the effect of his experiment. To judge the significance of what has occurred. In history there are no control groups. There is no one to tell us what might have been. We weep over the might have been, but there is no might have been. There never was. It is supposed to be true that those who o not know history are condemned to repeat it. I don't believe knowing can save us. What is constant in history is greed and foolishness and a love of blood and this is a thing that even God--who knows all that can be known--seems powerless to change.