Ivan Sag, the Sadie Dernham Patek Professor in Humanities and a professor of linguistics and of symbolic systems at Stanford, died Sept. 10 after a long battle with cancer. He was 63, and is survived by his wife, Penny Eckert, a professor of linguistics at Stanford.

Ivan Sag is remembered by his colleagues for mentoring students and rallying the linguistics community to promote the discipline. (Image credit: Felix Bildhauer)

The author or co-author of 10 books, Sag made notable contributions to the fields of syntax, semantics, pragmatics and language processing.

Using his own precise, formal theories of grammar, Sag “uncovered new phenomena, provided counter-examples to widely held beliefs about what is and is not possible in languages, and shed new light on the relationship between form and meaning in language,” said Tom Wasow, the chair of the Stanford Department of Linguistics.

A fellow of the American Academy of Arts and Sciences and the Linguistic Society of America, Sag will be remembered for his intellectual integrity and infectious enthusiasm for the field of linguistics.

“Ivan was really passionate about linguistics, about understanding what makes human language possible, and he had great charisma for communicating this passion. You couldn’t be around him without wanting to understand the answers to the questions he was always asking,” said his colleague in the Department of Linguistics Professor Dan Jurafsky.

Intersecting with cognitive science and psycholinguistics, Sag’s research advanced natural language processing (NLP) and contributed to computational linguistics by providing grammars that were sufficiently explicit to be implemented on computers.

Sag’s influential publications include Generalized Phrase Structure Grammar, Head-Driven Phrase Structure Grammar and Syntactic Theory: A Formal Introduction.

“No other linguist matched his combination of attention to formal rigor, empirical grounding and broad coverage,” said Wasow, who co-authored numerous works with Sag.

Sag was a senior researcher at the Center for the Study of Language and Information (CSLI), which he helped to found in 1983. Sag also sat on the committee that created Stanford’s Symbolic Systems Program, and served as the program’s director for five years (2000-01 and 2005-09).

Sag “saw grammatical theories as components of theories of how the human mind functions,” and his contributions, Wasow said, are “very influential among those natural language processing researchers who think a truly robust NLP system will ultimately have to incorporate grammatical knowledge.”

Sag’s work formed the basis of a number of computational systems around the world, including the CSLI LinGO system, which is being used as a tool for teaching writing in Memphis public schools.

In addition to his academic work, Sag will be fondly remembered as the founder and leader of Dead Tongues, the unofficial rock ‘n’ roll band of the Department of Linguistics.

Jurafsky, who played in Dead Tongues with Sag, said it was much more than a department band – an intellectual community where band members spent as much time “discussing linguistics in Ivan’s kitchen during breaks” as they did rehearsing.

Students, Jurafsky recalled, were generally singing and playing lead guitar. “That was just like Ivan: always making sure the students were out in front, showing off their stuff to the world.”

Linguistics keystone

Colleagues said Sag was nothing short of a keystone in the linguistics world, mentoring students well into their careers and rallying the linguistics community to promote the discipline.

“He got things done: workshops organized, contacts made, groups of people brought together, collaborative projects developed,” said linguistics scholar Geoff Pullum, a longtime academic collaborator and friend of Sag’s.

“The whole profession will mourn him,” Pullum said.

For more than three decades, Sag was an active member of the Linguistic Society of America (LSA), organizing numerous conferences and events. He taught in at least 10 of the LSA’s summertime linguistics institutes, which are hosted at a different university biennially. He directed the 1987 institute at Stanford and served as associate director at three other institutes.

As Wasow recounted, Sag liked to rent large houses so institute participants could live together. Those houses, Wasow said, were “crucibles for new ideas and collaborations.”

In 2005, citing Sag as an “effective citizen of the larger linguistics community, not just here in America but throughout the world,” the LSA awarded him the Victoria A. Fromkin Lifetime Service Award for distinguished contributions to the field of linguistics. In 2011, he held the Edward Sapir Professorship at the LSA’s Linguistic Institute at the University of Colorado-Boulder.

Sag was dedicated to teaching at Stanford and received a Dean’s Award for teaching in 1982. He routinely tapped his graduate students to co-author work with him.

“Ivan had a great wisdom for helping students develop the ability to criticize constructively, whether it was a paper they were reading or just questioning each other’s assumptions,” said Jurafsky.

Sag rarely missed an opportunity to confer with his students – past and present – and regularly invited them to his home. “Ivan would cook students dinner and have classes in the evening and talk about grammar over beer, and throw a barbecue or a jam session if [former students] were in town,” Jurafsky said.

Many of Sag’s former students returned to Stanford in April 2013 to attend a three-day workshop in honor of the 40th anniversary of Sag’s entrance into professional life. Officially titled “Structure and Evidence in Linguistics,” the event came to be known as “Ivan Fest.”

A tribute page on the accompanying website features moving entries by former colleagues and students describing how Sag influenced them personally and professionally.

Inbal Arnon, PhD ’10, who worked with Sag, wrote: “His taste for big questions, his endless curiosity about language, his appetite for life and for solving linguistic mysteries have all served as an example for how exciting and lively intellectual life can be. From the start, Ivan has not only been an exceptional mentor, but also a great friend.”

An idea generator

During the last 30 years of his career, Sag developed and refined formal theories of grammar that were, as Wasow put it, “precise enough to be computationally implementable and well suited to expressing linguists’ insights about language structure.”

Sag was one of the originating developers of Generalized Phrase Structure Grammar (GPSG), Head-Driven Phrase Structure Grammar (HPSG) and Sign-Based Construction Grammar (SBCG), with each stage developing out of the last.

Pullum, who co-authored Generalized Phrase Structure Grammar (1985) as well as numerous papers with Sag, called him “an idea generator” and a “master of syntactic and semantic data,” who was “constantly enthusiastic, always eager to investigate further, consummately honest about whether an analysis worked or not.”

Born in Alliance, Ohio, in 1949, Sag became interested in linguistics at the University of Rochester, where he studied Indo-European languages, sociolinguistics and Sanskrit. After receiving a BA from the University of Rochester in 1971, he went to the University of Pennsylvania, where he earned a master’s degree in 1973. Pursuing his interest in grammatical theory at the Massachusetts Institute of Technology, Sag wrote a dissertation on ellipsis (advised by Noam Chomsky). Sag earned his PhD from MIT in 1976. Before joining the faculty at Stanford in 1979, Sag was an assistant professor at the University of Pennsylvania for three years.

Sag was Professor Honoris Causa at the University of Bucharest (Romania, 2001). He was a fellow at the Center for Advanced Study in the Behavioral Sciences (Stanford, 2002-03); at Logica, the Dutch Research School in Logic (Utrecht, 1994); an Ameritech Fellow (Chicago, 1987-88); and a Mellon Fellow (Stanford, 1978-79).

He also served on the editorial boards of several journals, including Journal of Linguistics, Linguistics and Philosophy, Semantics and Pragmatics, French Review of English Linguistics, Journal of Language Modelling and Constructions.

There will be no public memorial service, but Sag’s family, friends and colleagues have joined with the LSA to found the Ivan Sag Linguistic Institute Fund to support the continuing efforts of the LSA to sponsor and organize the biennial Linguistic Institute, including student fellowships and the Sapir Professorship.