In The Brothers Karamazov, Ivan Karamazov says that if God does not exist everything is permitted. In a similiar way Richard Posner, who is himself an Appellate court judge in the US Seventh Circuit, in How Judges Think asks if legalism is dead then is everything permitted to judges? The strict adherence to the letter of the law isn't dead particularly in the lower courts. But in the higher courts of the United States where judges must rule on cases where pre-existing materials do not exist, Posner argues that judges potentially take on a political and legislative role. So if you're interested in the influences on how judges decide cases in the US higher courts, this is the book for you.