The thought occurs because Rushton's portraits are currently to be found not, as they usually are, in the store rooms at the Saatchi Collection, but in the company of a room full of ecclesiastical paintings at the Bowes Museum. Surrounded by flamboyant agonies and ecstasies, annunciations and lamentations, their reticence, their apparent aspiration to insignificance, is hard to miss.
You might say the same about today's younger artists. The museum's current exhibition, "Private View", which involves integrating work by 35 of them, from Britain and Germany, among the permanent exhibits sounds like the recipe for a violent culture clash. In fact, the imported works are often so self-effacing that the whole exercise begins to feel like some sort of avant-garde treasure hunt. Is there really nothing subversive in the Roman Archaeology room? Could these decorated buckets, pride of the souvenir shop, represent some stroke of unfathomably recherche satire? This creeping paranoia is only intensified by the discovery that one of the seemingly innocent museum notice boards is really a work by Peter Zimmermann.
Paranoia is not an entirely inappropriate response. The work here takes a variety of forms (from ceramics to photographs, videos to stuffed specimens of imaginary animals), but most seem to be devoted to unsettling our experience of the museum as a whole. Richard Wentworth, for example, has taken a space in a gallery devoted to display cases full of ceramics. On the top of one of these, he has perched a sheet of glass, precariously supporting several badly patched up pieces of crockery. It doesn't take long to realise he is looking to draw our attention to the way functional objects have been fetishised, in the gallery setting, as aesthetic. The real shock comes when you notice that the display case in question is balanced rather unevenly on bricks - and that its contents are themselves quite badly knocked about and undistinguished. Here, an the top floor, after yards and yards of Dutch landscapes (not to mention, in a temporary exhibition, Velazques's Rokeby Venus) we have reached the point of accepting almost anything on trust. We have fallen prey to the myth of Museum Quality, and abandoned our duty to look and think for ourselves. We have come to admire the museum, not its contents.
Not that admiring this particular museum, which is built in the style of a French chateau, is necessarily wrong. It was built in the 1870s by John and Josephine Bowes to house a collection that has barely been added to since their deaths, and which still includes a large number of Josephine's own refreshingly dreadful landscapes. Reflecting as it does the tastes and whims of two extravagant enthusiasts, it's a place where idiosyncrasies help to undermine its potential pomposity: there's a spectacular predella painting here by Sassetta, not to mention the two Goyas and El Greco's great Tears of St Peter, but there is also a life-size mechanical silver swan, a two-headed calf and an improbable number of potted palms. It is, in other words, a personal collection, a composite portrait of its makers rather than a solemn account of a particular aesthetic. "Private View" helps to restate that basic truth by allowing two contemporary curators, Veit Gorner and Penelope Curtis, to select contemporary works. According to the press release "the selection should give a fair representation of the diversity of current art practice", but it works so well precisely because it does nothing of the kind: their selections are as provisional and personal as those of John and Josephine Bowes.
The great surprise is the seamlessness with which the new works have made themselves at home here. They are not "site specific", and one would have expected them to jar. But perhaps that surprise is misplaced. After all, the supposed authority of the past, symbolised by the museum, is the recurrent obsession of the post-modern art world: we tend to define ourselves not by brave new initiatives, but by refusing to accept at face value the traditions we have inherited.
Katharina Fritsch's Ghost and Pool of Blood consists of what appears to be a figure, which we assume to be female, perhaps seven-feet tall, and entirely obscured by the white cloth draped over it: on the floor, a few feet to one side, we see a puddle of blood. Those folds of white- draped cloth, the trademark of neo-classical statuary, have completely obscured our sense of the body as a thing of flesh and blood. In aestheticising the body, and in particular the female body, our art tradition eventually denied it altogether.
Ghost and Pool of Blood would be a striking, even a beautiful object anywhere, but here, surrounded by ancient paintings and marble carvings, it suddenly becomes articulate. That is partly because, in the clinical world of the contemporary gallery, one could read Fritsch's work as a simple denial of the past - but here it is identifiably a part of the tradition it criticises. It does not look out of place, not least because that tradition has, however we may sterilise it as Our Great Heritage, always been defined by a similar process of questioning and change.
I don't mean to imply that there has not been a huge change in artists' attitudes and ambitions. The fascination with the idea of the museum is itself a marker of that change - artists tend to regard themselves as being involved in a conversation with the culture in which they find themselves and do not, on the whole, expect to be revered after their deaths or even, for the most part, during their lives. Like Emma Rushton's clerics, they do not aspire to the status of heroes, let alone martyrs.
This is a democratic age: it was all but impossible, searching through the museum, to distinguish these notorious young men and women of the avant garde from the other visitors in the galleries. East Coast Railways, which kindly agreed to provide free transport for artists and critics attending the exhibition, had politely declined to allow the artists and critics to travel on the same train - presumably because of the risk of some kind of fist fight. But when I did finally meet up with some of them, in a marquee on the back lawn, I found myself clutching a glass of wine in one hand, and a small child in another - it waslike attending a slightly up-market wedding, only rather better tempered.
n 'Private View' is at the Bowes Museum, Barnard Castle, Co Durham (01833 690606) until 28 July