Good News: PhD student solves an ancient Sanskrit problem

Rishi Rajpopat, a PhD student at the University of Cambridge, has solved a Sanskrit grammatical problem that has existed for 2,500 years. 

Sanskrit is the sacred language of Hinduism, dating back to around 1500 BC. It was codified by ancient Indian scholar and linguist Pāṇini into a text called the “Ashtadhyayi”. This text laid out the rules for how Sanskrit should be written and spoken.

Birch bark manuscript from Kashmir of the Rupavatara, a grammatical textbook based on the Sanskrit grammar of Panini © Wellcome Images

The text included 4,000 rules and was meant to work like a “language machine” into which you could feed the base and suffix of a word and then turn them into grammatically correct words and sentences through a step-by-step process. 

However, scholars found that often multiple rules seemed to apply at the same time. Therefore Pāṇini created a “meta-rule” to resolve the problem, which was interpreted by scholars as, "in the event of a conflict between two rules of equal strength, the rule that comes later in the grammar's serial order wins”. But this rule did not seem to solve the problem, as grammatical errors persisted. 

Rishi Rajpopat says he had a “eureka moment in Cambridge.” After months of getting nowhere with the problem, he took some time off studying. Then he returned to it, and “within minutes, as I turned the pages, these patterns started 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.” 

He realised that the metarule had been interpreted incorrectly, arguing that Pāṇini meant that when rules were applicable to the left and right sides of a word respectively, we should choose the rule applicable to the right side. This new interpretation of the rule works almost without exception.

It’s especially significant to scholars as it means that the grammar can now potentially be taught to computers. Rajpopat says that it could be “ a major milestone in the history of human interaction with machines, as well as in India's intellectual history.”

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