My mother’s brother, the Nobel economist Kenneth Arrow, died this week at the age of 95. He was a dear man and a hero to me and many others. No one else I have ever known so embodied the scholarly life well lived.

I remember like yesterday the moment when Kenneth won the Nobel Prize in 1972. Paul Samuelson—another Nobel economist and, as it happens, also my uncle—hosted a party in his honor, to which I, then a sophomore at MIT, was invited. It was a festive if slightly nerdy occasion.

As the night wore on, Paul and Kenneth were standing in a corner discussing various theorems in mathematical economics. People started leaving. Paul’s wife was looking impatient. Kenneth’s wife, my aunt Selma, put her coat on, buttoned it and started pacing at the door. Kenneth raised something known as the maximum principle and the writings of the Russian mathematician Pontryagin. Paul began a story about the great British mathematical economist and philosopher Frank Ramsey. My ride depended on this conversation ending, so I watched alertly without understanding a word.

But I did understand this: There were two people in the room who had won Nobel Prizes. They were the two people who, after everyone else was exhausted and heading home, talked on and on into the evening about the subject they loved. I learned that night about my uncles—about their passion for ideas and about the importance and excitement of what scholars do.

Kenneth’s writings resolved age-old questions and opened up vast new areas for others to explore. He likely was the most important economic theorist of the second half of the 20th century.