A grammatical problem that has beset Sanskrit scholars since the 5th century BC has finally been solved by an Indian doctoral student at the University of Cambridge, it emerged when his dissertation was published Thursday.
Rishi Rajpopat made the breakthrough by decoding a rule taught by Panini, known as the father of linguistics, which is now summarized in his thesis titled ‘In Panini, We Trust: Discovering the Algorithm for Rule Conflict Resolution in the Astadhyayi’.
According to the university, leading Sanskrit experts have described Rajpopat’s discovery as “revolutionary” and could now mean that Panini’s grammar can be taught to computers for the first time.
“I had a eureka moment in Cambridge,” recalls Rajpopat.
“After nine months of trying to solve this problem, I was almost ready to quit, I wasn’t getting anywhere. So I closed the books for a month and just enjoyed the summer, swimming, cycling, cooking, praying and meditating. Then I reluctantly went back to work, and within minutes, as I turned the pages, these patterns started to emerge and it all started to make sense. There was a lot more work to do, but I had found most of the puzzle,” said the 27-year-old scientist.
For the next few weeks, he was so excited he couldn’t sleep and spent hours in the library, including in the middle of the night, checking what he’d found and solving related problems. It would be another two and a half years before he would cross the finish line.
“Panini had an extraordinary mind and he built a machine unparalleled in human history. He didn’t expect us to add new ideas to his rules. The more we play with Panini’s grammar, the more it eludes us,” says Rajpopat.
The 2,500-year-old algorithm he decoded makes it possible for the first time to make precise use of Panini’s so-called ‘language machine’.
Rajpopat’s discovery makes it possible to “derive” any Sanskrit word, to construct millions of grammatically correct words, using Panini’s revered language machine, widely regarded as one of the greatest intellectual achievements in history.
Panini’s system — 4,000 lines described in his famous work, the Astadhyayi, believed to have been written around 500 B.C. — is meant to work like a machine. Enter the base and suffix of a word and it should convert them into grammatically correct words and sentences through a step-by-step process.
However, so far there is a big problem. Often two or more of Panini’s rules apply simultaneously in the same step, leaving scholars wondering which one to choose. Solving so-called “rule conflicts”, which affect millions of Sanskrit words, including certain forms of “mantra” and “guru”, requires an algorithm. Rajpopat’s research shows that Panini’s so-called language machine is also self-sufficient.
“My student Rishi has cracked it – he has found an extraordinarily elegant solution to a problem that has baffled scholars for centuries. This discovery will revolutionize the study of Sanskrit at a time when interest in the language is growing,” said Professor Vincenzo. Vergiani, professor of Sanskrit and PhD supervisor from Rajpopat.
Six months before Rajpopat made his discovery, Professor Vergiani gave him prescient advice: “If the solution is complicated, you are probably wrong”. An important implication of Rajpopat’s discovery is that now that there is the algorithm that executes Panini’s grammar, it could potentially teach this grammar to computers.
“Computer scientists working on Natural Language Processing gave up on rule-based approaches more than 50 years ago. So learning computers how to combine speaker intent with Panini’s rule-based grammar to produce human speech would be an important milestone. are in the history of human interaction with machines, but also in the intellectual history of India,” said Rajpopat.
Sanskrit is an ancient and classical Indo-European language from South Asia. Although spoken today by an estimated 25,000 people in India alone, it has influenced many other languages and cultures around the world.
“Some of India’s oldest wisdom has been produced in Sanskrit and we still don’t fully understand what our ancestors accomplished. We have often been given the impression that we are not important, that we have not put enough on the table. I hope this discovery will give students in India confidence and pride, and hope that they too can achieve great things,” added Rajpopat.