Jacques-Louis David completed The Oath of the Horatii in Rome in 1784 and exhibited it at the Paris Salon the following year. It stopped the room then. It still stops rooms now — visible here on the deep terracotta wall of the Louvre’s Denon Wing, large enough to command the gallery from any angle, the three brothers extending their sword arms toward their father in a gesture that has not lost its charge in two and a half centuries.