Solving grammar’s greatest puzzle

As Rajpopat struggled to make progress, his supervisor at Cambridge, Professor Vincenzo Vergiani, Professor of Sanskrit, gave him some prescient advice: “If the solution is complicated, you are probably wrong.”

“Six months later, I had a eureka moment,” Rajpopat says. “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.

“At that moment, I thought to myself, in utter astonishment: For over two millennia, the key to Pāṇini’s grammar was right before everyone's eyes but hidden from everyone's minds!"

“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 half years.”

_{Image: The Vākyapadīya of Bhartṛhari (5th century CE), a treatise on the philosophy of language belonging to the Pāṇinian school of grammar. Cambridge University Library (MS Add.876). Click here for more information about the Library's Sanskrit collections.}

Sanskrit is an ancient and classical Indo-European language from South Asia. It is the sacred language of Hinduism, but also the medium through which much of India’s greatest science, philosophy, poetry and other secular literature have been communicated for centuries.

While only spoken in India by an estimated 25,000 people today, Sanskrit has growing political significance in India, and has influenced many other languages and cultures around the world.

“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.”

Vincenzo Vergiani, Professor of Sanskrit at the University of Cambridge, says:

"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.”

A major implication of Dr Rajpopat’s discovery is that now we have the algorithm that runs Pāṇini's grammar, we could potentially teach this grammar to computers.

"Computer scientists working on Natural Language Processing gave up on rule-based approaches over 50 years ago", Rajpopat says.

“So teaching computers how to combine the speaker’s intention with Pāṇini’s rule-based grammar to produce human speech would be a major milestone in the history of human interaction with machines, as well as in India's intellectual history."

Pāṇini is thought to have lived in a region in what is now north-west Pakistan and south-east Afghanistan.

Rishi Rajpopat was born in a suburb of Mumbai in 1995. Rajpopat learnt Sanskrit in high school and Pāṇini's Sanskrit grammar informally from a retired Indian professor at no charge whilst pursuing his Bachelors in Economics in Mumbai.

Following a Masters at Oxford, for which he raised money by writing to hundreds of potential donors, Rajpopat started his PhD at St John’s College and Cambridge’s Faculty of Asian and Middle Eastern Studies in 2017 on a full scholarship funded by the Cambridge Trust and the Rajiv Gandhi Foundation. He was awarded his doctorate in January 2022. He recently joined the School of Divinity at the University of St Andrews.

Cambridge has a long history of studying Sanskrit, and Cambridge University Library holds a significant collection of Sanskrit manuscripts.

_{Images: Pages from the Bhagavad Gītā, written in Sanskrit, which presents in poetic form some fundamental spiritual concepts of Hinduism (India, 1824).}