It is always exciting to find a new image of a prominent Enlightenment figure! This portrait of Helvétius has been on the website of Lapham's Quarterly from at least 2015 and is beginning to feature more and more on the internet.....
Sadly, the subject is not the philosophe at all, but rather his father, the eminent doctor Jean-Claude Adrien Helvétius (1685-1755).
The anonymous painting belongs to the Musée de la Faculté de médecine in Nancy. where it is one of a set of seven portraits of teachers of the Royal College of Medicine, of which Helvétius was an associate member.
Joann – Claud. Adrian Helvetius. regis a Sanctoribus consiliis. Regina. archiater hujusce Collegii. Honor. Socius. obiit an 1755 AE71
"Jean-Claude Adrien Helvétius, member of the Royal Council, chief physician to the Queen, and honorary associate of this college. Died in 1755 at the age of 71 years."
The paintings hang in a smart modern gallery in the museum, on the Brabois Santé Campus of the University of Lorraine, Vandœuvre-lès-Nancy. You can just see the Helvétius in the photo below, from L'Est-Républicain:
|Photos. Musée de la santé à Vandœuvre : plongée dans la médecine d'antan (estrepublicain.fr)|