This is a rather famous painting by Arthur William Devis of the death of Lord Horatio, 1st Viscount Nelson belowdecks at the Battle of Trafalgar in the midst of the Napoleonic wars. While there are many such paintings/hagiographies of near-mythic generals and admirals in their dying moments, notably that of Wolfe's at the Plains of Abraham, this one is special for two factors: First, the artist took great pains to learn exactly who was present, what they were doing, and what they looked like, so that the painting serves as a (near) historical record. Second, because of the place Nelson and Trafalgar hold in the mythology that forms the root of Empire, in this case the beginning of the end of that of Napoleon and the birth of that of Britain. The use of art in this way is most likely exactly what Plato was looking for: a heroic martyr for the state, that, in dying, established a myth of invincibility that lasted for a century. What's astonishing here is that we don't have a similar paintings (maybe too few of our great heroes are killed in action?). Works of Lincoln's death are the only things that come close to establishing this kind of martyrology, while Washington is the only figure that approaches the deification that was afforded Nelson.
The case for a preferred status for disinterested art is pretty strong.