Cambridge student's 'eureka' moment solves centuries-old language puzzle for Sanskrit scholars

Rishi Rajpopa
Credit: PA
Indian PhD student Rishi Rajpopat, 27, decoded a rule that had confused scholars for centuries. Credit: Cambridge University

A Cambridge University student has solved a grammatical problem which has perplexed language scholars since the 5th Century BC.

Indian PhD student Rishi Rajpopat, 27, decoded a rule taught by Panini, a master of the ancient Sanskrit language who lived around 2,500 years ago.

Sanskrit is only spoken in India by an estimated 25,000 people out of a population of more than one billion, Cambridge University said.

But it is the sacred language of Hinduism and the medium through which much of India's greatest science, philosophy, poetry and other secular literature has been communicated for centuries.

Panini's grammar, known as the Astadhyayi, and written around 500BC, relied on a system that functioned like an algorithm to turn the base and suffix of a word into grammatically correct words and sentences.

A stamp issued by India in 2004 to commemorate Pāṇini Credit: Cambridge University

However, two or more of Panini's rules often apply simultaneously, resulting in conflicts.

Panini taught a "metarule" which is traditionally interpreted by scholars as meaning: "In the event of a conflict between two rules of equal strength, the rule that comes later in the grammar's serial order wins".

However, this often led to grammatically incorrect results.

Mr Rajpopat rejected the traditional interpretation of the metarule.

Instead, he argued that Panini meant that between rules applicable to the left and right sides of a word respectively, Panini wanted users to choose the rule applicable to the right side.

Employing this interpretation, Mr Rajpopat found Panini's "language machine" produced grammatically correct words with almost no exceptions.

Mr Rajpopat said he had a "eureka moment" after his supervisor at Cambridge, Professor of Sanskrit Vincenzo Vergiani, advised him: "If the solution is complicated, you are probably wrong."

He said: "After nine months trying to crack this problem, I was almost ready to quit, I was getting nowhere. So I closed the books for a month and just enjoyed the summer, swimming, cycling, cooking, praying and meditating.

"Then, begrudgingly I went back to work, and, within minutes, as I turned the pages, these patterns starting emerging, and it all started to make sense.

"There was a lot more work to do but I'd found the biggest part of the puzzle.

"Over the next few weeks I was so excited, I couldn't sleep and would spend hours in the library including in the middle of the night to check what I'd found and solve related problems.

"That work took another two-and-a-half years."

He added: "Some of the most ancient wisdom of India has been produced in Sanskrit and we still don't fully understand what our ancestors achieved.

"We've often been led to believe that we're not important, that we haven't brought enough to the table. I hope this discovery will infuse students in India with confidence, pride, and hope that they too can achieve great things."

He hopes it will now be possible to teach Panini's grammar to computers.

Professor Vergiani said: "My student Rishi has cracked it - he has found an extraordinarily elegant solution to a problem which has perplexed scholars for centuries.

"This discovery will revolutionise the study of Sanskrit at a time when interest in the language is on the rise."

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