Kripke was slight, bearded, in his early thirties. He was not well known but had a reputation as a genius. He had provided a completeness proof for modal logic (which deals with necessity and possibility) while still a teenager — and in the process reinvigorated Leibniz’s ideas about possible worlds. [2] There was also the amusing anecdote of Kripke being offered a chair at Harvard when he was 16. He supposedly wrote back, “Thank you, but my mother thinks I should finish high school first.”

By ERROL MORRIS

nytimes.com