Oliver Wendell Holmes Jr. 
Path of the Law [PDF ebook] 

The Path of the Law is a short essay by Oliver Wendell Holmes, Jr., an American jurist who served on the Supreme Court of the United States from 1902 to 1932. A cornerstone of his jurisprudential philosophy was the prediction theory of law, believing the law should be defined specifically as a prediction of how the courts work. In The Path of the Law Holmes argues that a criminal isn’t concerned about ethics or conceptions of natural law; they are concerned about avoiding punishment and jail. "The law", therefore, should be based on prediction of what will bring about punishment via the court system.