He is 78 and had been a judge since 1981, when President Ronald Reagan appointed him to the United States Court of Appeals for the Seventh Circuit, in Chicago. Before that, he was a prominent law professor who was among the leading figures in the movement to analyze legal problems using economics. In emphasizing social utility over, say, principles of fairness and equality, he gained a reputation as a cold and calculating conservative. That changed over time, and his recent opinions on voter ID laws, abortion, same-sex marriage and workplace discrimination based on sexual orientation have been decidedly liberal.