Plato sits at the end of the bed, slumped, an old man looking into his lap. He was not there. The account the painting follows is his own, and it says plainly that he was absent through illness. He was about thirty at the time, not seventy. David put him in anyway, and he had been advised to.
The scholar's letter
The commission came privately in 1786, from Charles-Michel Trudaine de la Sabliere, a rich young man of about twenty who had been taken with a drama Diderot once thought about writing and never wrote. David had already sketched the subject as early as 1782.
Now he went and got help. He consulted Father Jean Adry, a Hellenist, about what the day had actually been like, and one of Adry's letters survives. It tells David to show Plato immobile — and notes, in passing, that Plato was not in fact present. It asks for more emotion from Crito, and for Apollodorus, at the far right, to be visibly in pieces.
So the anachronism is not a slip. It is a decision taken on advice, and it makes the picture partly about the telling of the story rather than only the thing told.
Two signatures
David signed the canvas twice. His full name is under Crito, the man gripping Socrates by the thigh. His initials are under Plato.
The initials credit the source: everything anyone knows about this room comes from the Phaedo, which Plato wrote. The full signature under Crito is where the painter put himself, beside the friend who is still holding on.
Everything else is arranged around a man who will not stop teaching. Socrates has one hand up in the air, mid-sentence, and reaches for the cup with the other without looking at it. The man handing it over has turned his face into his own hand. On the stairs at the back, Xanthippe is being led away, having already been sent out.
Shown in 1787, and what came after
It went to the Salon of 1787 into the same rooms as another Death of Socrates, by Pierre Peyron, who had been David's rival for the directorship in Rome. The comparison settled that question.
Thomas Jefferson, then the American minister in Paris, wrote that David's was the best thing in the Salon and called it superb. Joshua Reynolds went further and said it was the greatest work of art since the Sistine Chapel and Raphael's rooms in the Vatican. David showed it again in 1791, when a picture about dying rather than recanting read rather differently.
Trudaine and his brother went to the guillotine in 1794. The painting stayed with the family, moved through private hands for a century, and was bought by the Metropolitan Museum in 1931.
The man who paid for it was guillotined in 1794. The picture about dying well outlived him by a long way.
Some stories are better over a coffee. Fifteen minutes with someone — audio only, not open yet.