Not so long ago I read an interview with Richard Wentworth in which he claimed to find 'cigarette packets folded up under table legs more monumental than a Henry Moore'. Asked why, the artist listed five reasons: 'Firstly, the scale. Secondly, the fingertip manipulation. Thirdly, modesty of both gesture and material. Fourth, its absurdity and fifth, the fact that it works.' Folded cigarette packets are difficult objects. The awkward kid brothers of Moore's bombastic Modernism, they nag away at our definitions of sculpture, combining shoddy aesthetics with functional purity, formal elegance with a trashy past. Walking around 'The Object Sculpture' at the Henry Moore Institute, I almost expected to glimpse one crammed beneath a bench or propping up a wobbling plinth. Somehow their presence hung over the show like a thick tobacco fog.
Selected by the artists Tobias Rehberger, Joëlle Tuerlinckx and Keith Wilson, the exhibition was a response to the question 'What is sculpture now?' It's a tough question, the kind that philosophers dissect word by word, frowning over each contentious element. Even 'now' is a pretty tricky notion. Does it mean 'right now' or 'over the last few years'? Is it just a chronological concept, or is it a cultural one too? Here, at least, 'now' meant works still testing the artists' imaginations, objects that continue to prickle and provoke. The oldest sculpture in the show, Medardo Rosso's Gli Innamorati sotto il Lampione (The Lovers under the Lamppost, 1882), emanates an insistent menace that felt uncomfortably contemporary. Modelled with stubby, intrusive fingers, its dirty bronze figures fought and fumbled under a glowering gas lamp. The work's side-table scale made it even more unnerving, a casual domestication of shabby sexual aggression.
Street lights also featured in Olafur Eliasson's Room for One Colour (1997-2002), a collection of humming sodium lamps that swamped the institute's art library with a dull nectarine glow. The lanterns bleached the books' wordy spines, turning them into abstract geometrical solids, fusing the volumes into a single blocky mass. Like a soft voice telling you not to think any more, Eliasson's piece was horribly seductive. Perhaps the artists chose it because it says something about a certain sculptural impulse, about trying to collapse art history into a single formal object. It's a dangerous idea, but bad things tend to happen when night falls and the streets turn a gloomy shade of orange.
The artists selected a number of works that shared a cranky faux utility. The dismal bunting of Thomas Schütte's Schwarze Girlande (Black Garland, 1980) might brighten up your party, but only if you were having it in a funeral parlour. The transparent loudspeaker of Philippe Parreno's Grand Prix, Monaco, 1997-1995 (1997) certainly looked useful, but its delicate glass curves would be shattered by the roar of the racetrack. Two mismatched fruit halves speared with teeth-shattering screws, Urs Fischer's Apple-Pear (2000) was doubly dysfunctional. Hung from the ceiling, the piece slowly decomposed around its hidden metal components. Playing on sculpture's cocksure longevity, it was a toothsome image of what happens when the rot sets in.
If some of the exhibits came across as unrepresentative curios, this was because the show was about sculpture rather than sculptors. Matt Mullican's familiar computer simulations and urban cosmologies looked out of step with most sculptural practice, but by selecting Untitled (Model Elements) (1993) the three artists chose a work that combined Mullican's melancholy interest in collapsing systems with a discrete three-dimensional object. At first glance it's a rather dowdy pile of coloured balls slumped on a white platform. Peering closer, though, I noticed that the platform was streaked with tiny lines of pigment, deposits left by the spheres in sprightlier, more energetic times. In a world where old certainties are withering away, maybe sculpture's suffering from entropy too.
Perhaps inevitably, the exhibition didn't really define what sculpture is now. The artists' choices were pretty idiosyncratic and I doubt they ever intended to create an even-handed survey. But from Paul Thek's cyborg L-Column (1966) to the plodding notes of Jonathan Horowitz's Bach Two-Part Invention #9 (1988) each of their selections triggered a sculptural kind of thinking. In the end the word 'sculpture' - like 'painting' - represents a method of understanding the world rather than a coherent collection of objects. Outside the walls of the Henry Moore Institute most of the exhibits would be just plain art. However, as Richard Wentworth points out in his description of the folded cigarette packet, context is everything. In this space at least, each work felt oddly monumental.