The small oval portrait was discovered hanging high on a wall in a home by an expert at the Enchères-Champagne auctioneers in Epernay, who had been tasked with an estate inventory.
The family had not paid any attention to the painting in years, but the expert noticed a barely legible inscription of the artist's name on the back of its gilded frame.
"Despite the layers of dust and the yellowed varnish, the energy of his painting remains perfectly recognisable," said Stephane Pinta of the Turquin expertise firm in Paris that authenticated the work.
Unlike the sensual pastel scenes that secured Fragonard's place in the pantheon of 18th-century masters, the muted illustration of the philosopher poring over his texts was one of just a handful of aged men he depicted.
It dates from 1768-1770, when Fragonard was moving beyond his more whimsical scenes of stolen kisses in gardens to explore more contemplative subjects that nonetheless exalted the pleasure of painting.
It also appears to have been executed with the artist's trademark virtuosity and speed, Pinta said: "The paint seems to be moulded or sculpted, at times even applied directly with a finger."
"The artist has reached the summit of his talent. Freed from the extreme minutia of the Rococo style, his brush strokes are quick, precise and incredibly expressive," he said.
Its value has been estimated at 1.5 to two million euros ($1.8 to $2.4 million) for a sale set for 26 June in Epernay.
(with AFP)
