Arts: Make it up as you go along

At long last, a group show with a decent theme! 'Thinking Aloud' celebrates creativity as making-do and mending.

Rude words first. The themed group show - cui bono, for God's sake? Anybody who frequents the contemporary art world will be aware that there's a large class of curators keeping it going, and that one of their main jobs is to think up half-cocked concepts around which to organise group exhibitions. So you get shows called things like Down the Plughole: New Art from the Bathroom, which will feature 20-odd works that are said to "explore notions of hygiene, waste and personal privacy" - an invented example, but they're easy to invent - and almost every group show has to have something like it.

Now group exhibitions are important. They're one of the main ways that new and not very well-known work gets its first public outing. A theme-based selection process is exactly what you don't want. For what happens? Your curator will start off with two or three decent works in mind which roughly fit the bill - indeed, which may have suggested the bill in the first place. But then they have to fill out the show with art which either doesn't really fit, or does fit but isn't much good.

So the theme procedure both imposes a probably irrelevant interpretative package as the very condition of display, and actually ensures that bad art will be favoured over good. The only people who clearly benefit are the curators themselves, pleased with this chance to exercise what they may believe to be their creativity; and another lot of people, usually described as "lecturers", who get to write the catalogue essays that expound the wretched themes (a species of crank literature if ever there was one).

And who needs themes at all? Does the public demand them? Why not cut all this crap, and have the selectors simply make it their business to round up and present, more or less miscellaneously, any new work they can candidly admire? Not Down the Plughole - but Twenty More Excellent Artworks. Or are these themes a handy cover for curators who can explore notions till the cows come home, but can't tell better work from worse? Eh?

I'm thinking about curating, having just been to Thinking Aloud - a South Bank Touring Exhibition, currently occupying all three galleries of The Cornerhouse in Manchester. It is itself a kind of themed group show, but with differences. It's been got together, not by a professional curator, but by the sculptor Richard Wentworth. The exhibits aren't by any means all works of art. And it's not obvious, either, what the theme governing this miscellany of objects is. In fact, trying to work out its linking principles is the show's chief and irresistible pleasure.

What would you say? Here are some of the things. Prosthetic hands. Architects' rough sketches - for the Crystal Palace and the Cenotaph. A doodle in red crayon made by Lloyd George at the Versailles Peace Conference. A Brassai close-up photo of a bus ticket someone has folded, half-torn and scrolled (entitled Sculpture involontaire). A Walker Evans photo of a small, poor town shop-window display. A 1989 Romanian flag with a torn hole where the Communist emblem used to be. A bird's nest with a right- angle (because it was built where two walls meet). A mould for a rubber tyre.

And here are some more. A piece of hastily fabricated Di memorial tat. The Blue Peter-style prototype for the Dyson vacuum cleaner. Wooden imitation sticks of dynamite. An archeo-physiognomic reconstruction of King Cyrus's head from his skull. Sundry maps, including Harry Beck's first draft for the London Underground diagram. Sundry toys, including a miniature model of an exploding shell-burst (came with a lead soldier set), and a game of Scrabble.

Enough to be going on with, but it's in the nature of the case that I'm not sure if this is a representative sample. Representative of what? Rather than a single concept, there seem to be a number of overlapping ones, such as: first thoughts and sketches, scale-models, temporary solutions, things jotted on the spur of the moment, alterations and adaptations and reworkings of existing stuff, imitations and reconstructions, substitutes, play versions and practice versions, everyday art. Connections jump and criss-cross all over the place. Most pieces exemplify several themes at once. Each of them is a tribute to the eye (Wentworth's) that made these rare finds - or again to the human culture that produced these rare gifts.

Take Stadthaus in Abruch: a German constructional toy from which you can build a scale model of a townhouse in the process of being demolished. Or take the exhibit whose caption goes: "Map plotted by a Dutch prisoner of war in a Japanese camp, WWII, showing the progress of troop advances on the Russian front, as interpreted from scraps of BBC radio broadcasts." What a trove! And what a world! The show's hero is not man the maker, but man the maker-do and mender. The god of ad hoc and DIY presides. Picking up clues and making mental links, we viewers feel we, too, are actively involved in the process.

So this is one of the most intelligent and lively bits of curating you're likely to find and, among exhibitions where the curation is the main spectacle, I don't recall seeing better. In fact it's so cheering and seductive that it's worth noting - for balance - the potential sentimentality of all this low-tech Crusoeism. It is, after all, a good thing that there are also some finished products in full working order in the world. Human improvisation is a wonder, but it's not always so wonderful.

For instance, I remember Wentworth once citing, as an example of everyday sculpture, people's tendency to set an empty drink can on top of a bollard, as if on a pedestal. You may think this observation pretentious. I think it's very true and acute - but too high-minded. Evidently the drinker can't be bothered to find a bin, but doesn't like to drop the can, and what's going on is disguised littering. It's disguised from passing witness, maybe even from the litterer himself - and disguised as, precisely, a neat, quasi-sculptural bit of balancing. But it'll fall off eventually, and someone else will have to clear it up. The moral isn't just creativity; it's creativity used as a blind.

That's mild enough. But Thinking Aloud might equally celebrate some undoubtedly malignant cases of improvisation. The dumdum bullet, for instance, or the nail bomb. There's lots of war stuff in the show, but no weapons; if you're going to praise human ingenuity, you must allow that much of it has been devoted to ripping humans apart. Or again, think about the defence of property. Those shards of broken glass cemented along the tops of walls - what could better fit Wentworth's bill? It's constructive-adaptive re-use of waste to a tee. But it's too bloody nasty.

I haven't mentioned any of the bona fide artworks yet. There are plenty, mostly of the transformed found object sort. They seemed slightly irrelevant. Granted, in any general survey of human creativity, the special creativity of artists is likely to be demoted, but the result isn't quite - as you might think - that intermingled here you can't tell the difference between art and curio. You can usually; but the difference is mainly that the art-object's interestingness looks like a laboured, self-conscious version of the non-art object's.

This isn't a point against art, though. Rather, art's been too successful for its own good. We've been taught by generations of post-Dada work to extract all sorts of interest from everyday things, so that we've got so good at it we can do it by ourselves and don't need artworks to help anymore. This is a situation that some of the old anti-art pioneers positively looked forward to. But now it seems to be actually happening. Barriers break down. Some people are going to be out of a job. The show is drawing good crowds, and they don't seem to care what's what.

Thinking Aloud - at The Cornerhouse, Oxford Street, Manchester until 28 February; closed Mondays; admission free. Then showing at Camden Arts Centre, 9 April to 30 May. A National Touring Exhibition from the Hayward Gallery