At 90, UCLA’s Judea Pearl is still asking the big questions

Judea Pearl has spent most of his life thinking about some of the hardest questions there are.

How can machines reason when they don't have all the information? How can scientists distinguish correlation from cause and effect? How can people divided by religion, culture and politics better understand each other? And, after the murder of his son Daniel, how does a parent make sense of the senseless?

On Sunday, Sept. 6, more than 50 colleagues, former students, friends and admirers gathered at UCLA, Pearl's academic home for the past 56 years, to celebrate the pioneering computer scientist as he turned 90 and to consider some of the questions that have animated his extraordinary career.

The daylong Pearl@90: Honoring Judea Pearl celebration at UCLA's Covel Grand Horizon Ballroom - organized by several of his academic protégés - covered broad terrain, much like Pearl's own interests and influence, with personal tributes and discussions exploring artificial intelligence and causal reasoning, Jewish identity, dialogue and coexistence, and peace.

UCLA Chancellor Julio Frenk, in his remarks at the event, lauded Pearl's enduring willingness to wrestle with some of the most challenging issues of his time.

"Judea has spent a lifetime in conversation with life's most difficult questions," Frenk said. "And in doing so, he has been a living testament to what higher learning makes possible."

Turning uncertainty into understanding

Pearl, Chancellor's Professor Emeritus of computer science at the UCLA Samueli School of Engineering, joined UCLA's faculty in 1970, when artificial intelligence itself was still a nascent field. Over the decades that followed, he helped fundamentally change it.

One of the problems that captivated him was deceptively simple: How can a computer make intelligent judgments when the information available to it is incomplete or uncertain?

His groundbreaking development of Bayesian networks provided a way for computers to represent complex relationships among variables and calculate how new information changes the likelihood of different outcomes. The approach transformed how researchers thought about reasoning under uncertainty and found applications well beyond computer science.

Pearl then pushed further, taking on one of science's oldest and most difficult problems: determining not merely that two things are associated, but whether one actually causes the other.

His mathematical framework for causal inference gave researchers powerful new ways to reason about cause and effect, influencing fields as varied as statistics, medicine, epidemiology, economics and the social sciences.

"Judea, you have been the heart and soul of the probabilistic revolution of AI," said Eric Horvitz, who met Pearl in 1984 while in his first year of graduate work at Stanford University. "That was more than 40 years now. Hard to believe. It seems like yesterday."

Pearl had read a paper by the young graduate student and sought him out. Horvitz recalled Pearl's passion as he raised his clenched fists and declared that "probabilistic networks are the foundation of human reasoning."

Horvitz would go on to pioneer the integration of probability theory and decision science into artificial intelligence to help computer systems reason under uncertainty. Today he is the chief scientific officer at Microsoft.

Frenk called Pearl "a pioneer of probability and a connoisseur of causality."

"He has laid the groundwork for modern AI, which is perhaps the most significant innovation of our lifetime, informing how we think about the capabilities, modalities and ethical complexities of this technology," Frenk said.

Pearl's work earned him the 2011 A.M. Turing Award from the Association for Computing Machinery, often described as computing's equivalent of the Nobel Prize. The association honored him for his "fundamental contributions to artificial intelligence through the development of a calculus for probabilistic and causal reasoning."

A member of both the National Academy of Sciences and National Academy of Engineering, Pearl was elected a foreign member of the U.K.'s Royal Society in 2025, and this year, the Boston Global Forum named him among 50 pioneers who have helped shape artificial intelligence.

Pearl brought his ideas to a broad audience in 2018 with "The Book of Why: The New Science of Cause and Effect," co-authored with science writer Dana Mackenzie. The book looked ahead to what Pearl sees as a necessary next step for artificial intelligence: moving beyond finding patterns in data to reasoning about why things happen and, importantly, what might have happened differently.

Conversations beyond computer science

Some of the most consequential questions Pearl has addressed, however, have nothing to do with machines.

He has long written and spoken about Jewish identity, antisemitism, Israel and the possibilities for dialogue and coexistence - including in his 2025 book "Coexistence and Other Fighting Words" - and he has engaged publicly with subjects where disagreements can be profound.

"For decades, he has come to the table ready to debate, to defend and to dialogue," Frenk said. "He has shown us that we can argue our differences passionately - even sometimes vehemently - but always respectfully."

Those issues had a place at the celebration as well. A late-afternoon panel featuring Rabbi David Wolpe and UCLA adjunct associate professor Steven Zipperstein explored peace, dialogue and coexistence.

The most difficult chapter of Pearl's life began when he was confronted with a tragedy no parent wants to contemplate. In 2002, his son Daniel, a Wall Street Journal reporter, was kidnapped and murdered by terrorists while reporting in Pakistan.

Pearl and his late wife, Ruth, responded to the loss in part by establishing the Daniel Pearl Foundation, seeking to carry forward their son's commitment to journalism, music and cross-cultural understanding.

"Once again, Judea showed us how to make sense of senselessness," Frenk said.

At UCLA, that legacy has included the Daniel Pearl Memorial Lecture Series, which, since its launch in 2002, has brought more than 20 eminent journalists, public officials and other prominent figures to campus to examine journalism, international affairs, tolerance and freedom of expression.

Still part of the conversation

Pearl's influence has extended across generations of students and scholars, many of whom were at the celebration.

"Beyond the huge impact he has had on AI, and beyond being ahead of his time, Judea had a huge impact on people," said Dan Roth, who met Pearl more than 25 years ago in Sweden.

Roth, Oracle's chief AI scientist and a professor of computer and information science at the University of Pennsylvania, said Pearl "inspired me and a lot of the work I have done. He really inspires people when he talks about life, when he talks about science, even when he talks about politics - and whether you agree with him or not."

For Pearl, whose career has revolved around uncertainty, one thing is firmly established: The ideas he developed at UCLA have traveled far beyond it, influencing how researchers across disciplines think about evidence, cause and effect, and, increasingly, intelligence itself.

There is another legacy as well, one rooted not in algorithms or equations but in his willingness to keep asking difficult questions and engaging with people over their answers.

Now, as he enters his tenth decade, Pearl shows no signs of letting up - and he is still giving UCLA and the world plenty to talk about.

Tags: faculty news | computer science | mathematics | artificial intelligence