Richard Posner, the federal appeals court judge whose formidable intellect and restless curiosity helped transform American legal scholarship, died this week in Chicago. He was 87.

A leading figure in the law and economics movement, Posner wrote more than 3,300 opinions during nearly 36 years on the U.S. Court of Appeals for the Seventh Circuit. He also authored or co-authored more than 50 books and published hundreds of journal articles, becoming one of the most cited legal scholars of his era.

Appointed to the Seventh Circuit by President Ronald Reagan in 1981, Posner became known for opinions that resisted easy ideological classification. In 2014, he wrote the court’s decision striking down same-sex marriage bans in Indiana and Wisconsin. He also publicly criticized conservative Supreme Court justices and clashed with Justice Antonin Scalia over legal interpretation.

Posner’s scholarly influence reached far beyond the courtroom. His 1973 book *Economic Analysis of Law* helped establish the study of how legal rules shape incentives and economic behavior. His subjects ranged from antitrust and contracts to sexuality, aging and adoption.

In a paper with Elisabeth Landes, “The Economics of the Baby Shortage,” Posner argued that adoption regulations could contribute to a black market by preventing supply and demand from balancing. The work drew debate over the implications of applying market analysis to adoption.

Yet Posner was not rigidly committed to a single economic orthodoxy. After the 2008 financial crisis, he published *A Failure of Capitalism*, examining the breakdown of markets and regulation.

His approach to judging was similarly pragmatic. In *Hively v. Ivy Tech Community College*, a 2017 case in which the Seventh Circuit held that federal law prohibits employment discrimination based on sexual orientation, Posner joined the majority but wrote separately to defend what he called “judicial interpretive updating.”

He argued that courts should acknowledge when they apply an older law in light of changed circumstances, rather than suggest that its authors anticipated every modern application. Three years later, the Supreme Court reached the same result under Title VII in *Bostock v. Clayton County*, using a different interpretive approach.

Posner retired abruptly in September 2017, citing the federal courts’ treatment of people who represent themselves. He later assisted William Bond, a self-represented litigant whose case ultimately reached the Supreme Court in an unsuccessful petition.

Tributes remembered both his intellectual reach and his warmth. Gus Hurwitz, a University of Pennsylvania academic, recalled debating films with Posner in a Chicago seminar. “Not only was the man a legend,” Hurwitz wrote. “He was a goofball. And fun.”

Columbia law professor Jamal Greene captured the breadth of Posner’s influence: legal academics, he wrote, had all “strenuously disagreed with something Richard Posner has written, and still they read the next thing.”