'He was in mystic delirium': was this hermit mathematician a forgotten genius whose ideas could transform AI – or a lonely madman?

One day in September 2014, in a hamlet in the French Pyrenean foothills, Jean-Claude, a landscape gardener in his late 50s, was surprised to see his neighbour at the gate. He hadn't spoken to the 86-year-old in nearly 15 years after a dispute over a climbing rose that Jean-Claude had wanted to prune. The old man lived in total seclusion, tending to his garden in the djellaba he always wore, writing by night, heeding no one. Now, the long-bearded seeker looked troubled. "Would you do me a favour?" he asked Jean-Claude. "Could you buy me a revolver?" Then, after watching the hermit – who was deaf and nearly blind – totter erratically about his garden, he telephoned the man's children. Even they hadn't spoken to their father in close to 25 years. When they arrived in the village of Lasserre, the recluse repeated his request for a revolver, so he could shoot himself. There was barely room to move in his dilapidated house. The corridors were lined with shelves heaving with flasks of mouldering liquids.