You need a real sense of history to appreciate the work of Paul Delaroche. First, you have to try to imagine what made his paintings so popular in the 1800s; then, you have to supply most of the footnotes yourself

In the Wallace Collection, last weekend, an old lady and her friend stopped in front of Paul Delaroche's famous painting, Edward V and the Duke of York in the Tower. They took in the scene for a while - the two boys huddled together in their cell, the ominous shadow cast underneath the door, the little dog who has sensed the intruder. Then the old lady said sadly to her friend, "A mysterious death." And then, shaking her head, "Terrible... terrible."

Overhearing other people's comments in art galleries is an easy way to feel superior, and at that moment I did feel myself to be more sophisticated than my fellow viewer - assuming that her "terrible" referred, not to the painting, but to the fate of its protagonists. But, on the other hand, she was right. That is the sort of response that Delaroche's work asks for. If you come away from this picture without your concern for the little princes quickened, then it's wasted on you.

It's 200 years since the artist's birth, and to mark the occasion the Wallace Collection has put together a small exhibition of its Delaroche pictures called "Death and Devotion". There are only a dozen paintings and watercolours, and a few prints, but it's enough to give you the general idea. It's a revival bid. In his heyday, the 1820s and 1830s, Delaroche was one of the most celebrated painters in France. But for most of those 200 years his reputation has been very low. They're not the sort of pictures we admire any more.

Well, I say "we", but that's clearly presumptuous. The picture of the little princes has remained a favourite with many, and the National Gallery's The Execution of Lady Jane Grey is a favourite, too. Go there now, and you'll see a crowd around it that the other pictures in the room - by David, Ingres, Courbet, Daumier, even Puvis de Chavanne's far more dramatic Execution of John the Baptist - signally fail to draw. That crowd doesn't need its interest revived. No, "we" has to mean we sophisticated viewers: we who know how to use the words "sentimental" and "anecdotal", we who can only, and at best, find Delaroche's work "interesting". Still, we can at least do that. And we can learn something about the tastes we lack.

Oddly enough, we'd probably like it more if it was more violent. Delaroche's typical subjects certainly promise drama: political murder, the death of kings. "The court painter to all the beheaded Majesties," the poet Heine called him. But he stages them with a deliberate lack of drama. His pictures belong to a class called "historical genre" - historical episodes treated from an everyday-life angle. Delaroche avoids the public spectacle for the private glimpse. He avoids the moment of crisis for the uncertain moment before or after crisis. And this way he gets his own sort of drama, by holding the famous historic action at bay, by letting it hang over the scene, bear down on it, and fill it with implications.

In those terms, his scenarios can be very good. Take a picture not represented in this show, Cromwell and Charles, which shows the General alone with the dead king's coffin, lifting the lid, brooding solemnly over the body. There's no action, nor is the incident itself strictly historical. But it focuses plenty of historical reflection. It asks you to imagine what is going through Cromwell's mind, to supply his interior monologue - thoughts about the enormity of regicide, about the power and responsibility that now devolve on him, about the king at peace and the struggle ahead. It's not hard to read all this in it, the scene provides the perfect cue. But the picture itself says nothing: a human encounter that, without its title, would be almost inarticulate.

So the pictures don't tell stories. They prompt the viewer to fill in the story. They demand it. You have to know and feel the history that's displaced to get the effect. His art is addressed to the mind with the minimum of bodily or painterly expression. The starkest contrast is with his exact contemporary Delacroix, for example with Delacroix's The Death of Sardanapalus. In that picture, what you see is what you get - a sumptuous orgy of paint and slaughter. It's a history painting that requires no knowledge, apart from vague ideas about oriental despotism and its monstrous ways. You don't get more out of it by wondering what precisely's going on.

But the tender moment enacted in Lady Jane Grey needs background. A young woman is being gently helped to the block. The axeman stands by. But all the essential affective information is off-stage - the "Nine Days' Queen", dynastic pawn and political victim - those are the thoughts the scene is there to precipitate. What's more, there's no thrill of imminent decapitation to distract from this. There's a big, square axehead waiting at the side of the canvas, and there are countless ways a painter might have hinted at the coming chop. But Delaroche refuses all opportunities of physical sensation, just as he keeps the murderers well out of The Princes in the Tower.

Delaroche didn't avoid violence entirely. There's blood on the flagstones in The Assassination of the Duc de Guise. It's quite a brutal picture - just because it shows not the act but the comedown afterwards. The assassins stand around in a huddle in the left half of the scene. The right half is almost empty, except for the corpse, abandoned flat out on the floor at the far edge, denied any dignifying aspect of martyrdom as the assassins are denied the energy of action. Then the French king steps in shiftily, far left, to find his orders carried out. It's his reaction and tormented mind that we're to let our minds expand on.

History doesn't just become private in Delaroche's hands. It becomes, in a way, meaningless. Traditional history painting from Poussin to David had been concerned to stress significance, to provide elevated examples from the past, or awful warnings. But, for Delaroche, seeing everything in human terms, history is a supply of pathos. He's not involved with politics, public virtues, decision-making. History is something that happens to people. He dwells on its victims. Or, when he shows power, it is power baffled or power fading, as in a painting here of Cardinal Mazarin's Last Sickness, the statesman still playing cards from his deathbed amid a chattering court.

Still, you do need to have a grand sense of history, of great men and women, and great deeds. You need it to provide the emphasis for these human moments. And, I think, for that reason, you could call Delaroche's art exploitational. It wants to have the big themes around to add the needful emphasis and aura and contrast, while not being at all interested in them. Of course, this is an attitude that sustains much historical fiction and sustains much of the work of the National Trust, too.

But probably "our" main difficulty with the work is more aesthetic. Delaroche is no brush-man, and his clean textures can be dull or worse - it's not just that, though. It's the way his pictures require you to take an intimate, novelistic interest in their characters for no reason that the pictures themselves offer. You have to know the story, and feed it in (famous history, but it could be any sort of tale). You have to write the play around the tableau. But the puzzle is that, once you accept this premise, the thing can obviously work very well, as these images often do: by doing very little, just supplying a well-judged catalysing nudge to the responsive mind. In fact, this soul-speaking is a species of conceptual art. So maybe Delaroche is due for a comeback.

To 12 Jan, Wallace Collection, Manchester Square, London W1 (0171-935 0687). Admission free