Paul Benacerraf, preeminent philosopher of mathematics, Princeton alumnus and ‘life-changing teacher,’ dies at 93

Paul Benacerraf, the James S. McDonnell Distinguished University Professor of Philosophy, Emeritus, died at his home in Princeton on Jan. 13. He was 93.

A member of Princeton’s undergraduate Class of 1952, he earned his Ph.D. at Princeton in 1960 and joined the University’s faculty that year. He taught for nearly five decades, served as provost from 1988 to 1991, and transferred to emeritus status in 2007.

“Paul Benacerraf was a field-defining scholar, a much-loved teacher and a defining presence in the philosophy department,” said Benjamin Morison, professor of philosophy and department chair. “His brilliant work in the philosophy of mathematics has achieved classic status. He was a demanding teacher — but one who was also extraordinarily kind and encouraging to graduate students and more junior colleagues.”

Morison also fondly remembers Benacerraf’s “legendary cooking, which he shared as generously as he did his philosophizing. I still don’t believe that the utterly delicious dish he once served me was made of cauliflower.”

Mark Johnston, the Henry Putnam University Professor of Philosophy, said that Benacerraf, who was a longtime chair of the department, “did more than anyone else over the 1960s and ’70s to recruit the great and the very good, including Richard Rorty, Donald Davidson, Gilbert Harman, Tom Nagel, Saul Kripke, David Lewis, Bas van Fraassen, Tim Scanlon, John Burgess, Margaret Wilson, Michael Frede and John Cooper. So, Paul was, more than anyone else, the insightful creator of what became the preeminent department of philosophy for the next 30 years.”

Johnston continued: “He was a life-changing teacher and mentor for many undergraduate and graduate students in the department. And he was, for a time, provost. Add to all that his own seminal work in the philosophy of mathematics, and you have something approximating the Platonic ideal of a devoted academic. Whence comes such another?”

Benacerraf was born in 1931 to a Moroccan-Venezuelan father and Algerian mother in Paris, where his father was a textile buyer for the import business he had established in Caracas. At the outbreak of World War II, his Sephardic Jewish family fled to Caracas and then moved to New York when he was 9. When he was 11, his parents returned to Caracas and he entered the Peddie School in Hightstown, New Jersey, as a boarding student.

His interest in philosophy was sparked his senior year at Princeton, when he took classes in the philosophy of science with John Kemeny ’47 *49 (who worked on the Manhattan Project, was a mathematics assistant to Albert Einstein, and later became president of Dartmouth College) and in the philosophy of religion with Robert Scoon. As a graduate student, he studied with Paul Ziff and Hilary Putnam, who directed his dissertation. With Putnam (then at Harvard University), he later edited the anthology “Philosophy of Mathematics: Selected Readings” (Prentice-Hall, 1964), considered the standard anthology in the discipline.

Tackling questions of the human capacity to ‘have knowledge of the infinite’

In an interview with the Princeton Weekly Bulletin in 1998, Benacerraf said his interest in the philosophy of mathematics stemmed from questions about what human knowledge is and how we acquire knowledge of something like mathematics “that we have no direct or indirect sensory contact with. … Mathematics is where we study the infinite, both the infinitely large and the infinitely small. How can the finite beings we are have knowledge of the infinite? That's a real, not a rhetorical question."

His interests also focused on logic, epistemology, metaphysics, and the philosophy of language. Although he wrote widely on these subjects, he is best known for two of his early papers — “What Numbers Could Not Be” (1965) and “Mathematical Truth” (1973), the latter of which came to be called “the Benacerraf problem.”

Paul Boghossian, who earned his Ph.D. in 1987 and is the Silver Professor of Philosophy at New York University, said those two papers “became instant classics and are discussed to this day.”

Boghossian continued: “His external toughness and sardonic wit covered up a very warm heart which he showed especially to students. He took me under wing, inviting me to his wonderful house for dinners. When I was floundering with my thesis somewhat, he saved my whole career (I would say) with his close mentoring and advising.”

“Paul was a brilliant mentor and adviser, not just for me but for a significant number of students in the program at the time,” said Gideon Rosen, who earned his Ph.D. in 1992 and is the Stuart Professor of Philosophy at Princeton. Benacerraf at one point had so many graduate students, including Rosen, that he convened a special seminar for them in which they would present their work to one another. That seminar eventually became the department’s dissertation seminar, now a central component of the graduate program.

“Some great teachers are great because they are unfailingly supportive. That was not Paul’s style,” Rosen said. “If Paul thought your work was bad, he would tell you. And yet he had a way of doing this that conveyed first, that this was normal — philosophy is hard, so lots of good philosophers do lousy work — and second, that it was not fatal; you would push through (with his help), and most of us did. Paul did not just stick with his students when the work was rough; he clearly relished his time with us. This showed that he had hope; and for me at least, that was encouragement enough.”

When Rosen became Benacerraf’s colleague in 1993, he saw yet another facet of his former adviser’s character. “Fierce philosopher that he was, Paul was warm and overtly generous to students and colleagues,” he said. “When I was an assistant professor and some formal event in the department was coming up, Paul overheard me in the hallway telling another colleague that I didn’t have a suit — that in fact I’d never had a suit.  The next day there was a brand-new suit hanging from my office door.”

One of Benacerraf’s sons, Nicolas, said his father was especially proud of his time as associate provost for special studies (1968-70), under then-provost William G. Bowen (later University president), when he worked on a study that helped demonstrate that admitting women to the University would be cost-effective. He served as associate dean of the Graduate School from 1965 to 1967.

The ‘truly delightful’ work of teaching

Despite his major accomplishments as a scholar, adviser and administrator, Benacerraf’s greatest love was the classroom. "To be present as students unfold philosophical mysteries for themselves, struggle to push back the darkness and, in whatever measure, succeed," he said in the 1998 Princeton Weekly Bulletin interview, "this is truly delightful."

Not surprisingly, the course he taught most frequently was “Philosophy of Mathematics,” designed as an undergraduate course but often attracting graduate students.

T.M. Scanlon, a 1962 graduate and the Alford Professor of Natural Religion, Moral Philosophy, and Civil Polity, Emeritus, at Harvard University, took that course as a junior, which led to Benacerraf advising his senior thesis. “That experience changed my life. Had it not been for Paul's encouragement and insistence, and criticism, I never would have gone into academic life,” said Scanlon, who taught at Princeton from 1966 to 1984. “He was a remarkable person, brilliant and tough, and caring.”

When Arun Alagappan ’81 was a sophomore, he desperately wanted to take “Philosophy of Mathematics,” but his class schedule prevented it. He went to meet with Benacerraf and asked, both nervously and boldly, whether he would consider teaching him the course material through weekly independent tutorials.

“Without question or hesitation, he agreed to a semester’s worth of private tutoring for a 19-year-old he had only just met,” Alagappan said. The way Benacerraf challenged him as a student “served as a catalyst for significant intellectual and emotional growth,” he said. The experience inspired Alagappan to found Advantage Testing, Inc., a tutoring and education counseling company, in 1986, and the Advantage Testing Foundation, a public charity whose mission is to advance the academic and professional ambitions of underrepresented, lower-income students. Shirley M. Tilghman, professor of molecular biology and public affairs, emeritus, and former University president, serves as its board's vice president.

Benacerraf’s many honors and professional affiliations include two Guggenheim fellowships. He was a member of the American Academy of Arts and Sciences, the American Philosophical Association, the Association for Symbolic Logic, and the Philosophy of Science Association, among many others.

Benacerraf is survived by his children: Marc, Tania, Andrea, Nicolas and Natasha, a 2011 Princeton graduate; his grandchildren Sophie, Lucas, Audrey, Dillon and Seth; his friend and former wife, Suzanne; his grandnephew, Oliver; and his grandniece, Brigitte.

A memorial will be planned in the near future.

His family said people may send contributions in Benacerraf’s honor to their local National Public Radio station.

View or share comments on a memorial page intended to honor Benacerraf’s life and legacy.