Rishi Rajpopat – The Cambridge Student Who Cracked Sanskrit's Greatest Puzzle

An Indian student at the University of Cambridge, Rishi Rajpopat, recently made the headlines for solving one of the greatest puzzles in Sanskrit grammar, which has evaded scholars since the fifth century BC.

The puzzle in question was about a rule taught by Panini, also known as 'the father of linguistics', in his grammar, Aṣṭādhyāyī.

"Panini wrote about 4,000 rules in his grammar that help us derive any word, and subsequently, any sentence of Sanskrit correctly," Rajpopat told The Quint.

He further said that the rules of Panini's grammar "work like a machine."

How does Panini's grammar work? Rajpopat said that to derive a grammatically correct word, one needs to feed in the base and suffix of the word and follow the step-by-step process as per Aṣṭādhyāyī.

Why was the puzzle so hard to crack? The problem that arises while deriving a word is that often two rules become simultaneously applicable at the same step.

"So, the question that arises is: which rule should we apply?"

Rajpopat said that Panini had "taught us many meta-rules in his grammar, out of which one deals with the problem of rule conflict."

A meta-rule is one that gives you instructions about how to interpret rules, and how rules interact with each other.

"That meta rule was misunderstood by Sanskrit scholars, starting with the very first commentators all the way up to now, or until very recently," he added.

The meta-rule in question is 'Rule 1.4.2 – vipratiṣedhe paraṁ kāryam,' in which "paraṁ" means "which comes after the other."

How was this meta-rule misunderstood? Traditionally, in the event of a conflict between two rules of equal strength, scholars used the rule that came later in the grammar's serial order. This often led to grammatically incorrect words.

How did Rajpopat fix this problem? "I re-interpreted the rule. So, instead of applying the rule which comes later in the serial order, I started using the rule which was applicable to the suffix, ie the right-hand side rule," Rajpopat said.

For example, he explained, if we want to derive the word 'Definition', which is made of define + ation, then we use the rule that is applicable to 'ation.'

Rajpopat also told The Quint how difficult it was for him during the first nine months of his research.

"The biggest challenge was the first nine months, where I couldn't find a thing. I mean, I couldn't really make any progress. I was trying different approaches, trying different methods, seeing what I could do differently every day, from what I had done the previous day. And I was doing exactly the same thing over and over. It was a repetitive cycle of failure and disappointment and gloom," he said.

'Milestone in India's Intellectual History'

Now that this puzzle has been solved, Rajpopat said, "We will now be able to teach the computer how to produce Sanskrit sentences using Panini's grammar."

"If this is successfully done, then this will be a great milestone, not just for India's intellectual history, but also in the history of human interaction with machines, more generally speaking," he added.

Rajpopat did his undergraduate in Economics from Mumbai. During that time, he learnt Sanskrit from a retired teacher in the city. Later, he moved to Oxford University to pursue a post-graduate degree in Sanskrit, after which he got a full scholarship at the University of Cambridge for his PhD.