The cadaver is not the subject.

In January 1632, in the weigh-house at Amsterdam, the city's anatomist Nicolaes Tulp dissected the left forearm of a hanged thief named Aris Kindt before a paying audience of seven surgeons and a room of onlookers. Rembrandt, then twenty-five, painted the scene. We know the result as The Anatomy Lesson of Dr Tulp, and we assume the cadaver is its subject, because the cadaver lies at its centre and everyone in the frame is looking at it.

But the cadaver is not the subject. Look again and the dead thief becomes what he was on the table that morning — a catalyst, the thing that makes everything else happen. The real subject is the looking itself: the faces ranged above the body, each one lit and quickened by the act of attention into something far more alive than the thing it attends. This is not a private reading. Sebald opens The Rings of Saturn in front of this painting; its better critics have said as much for a long time. The subject of The Anatomy Lesson is an audience, caught in the act of becoming one.

Everything KMA made between 2005 and 2020 was, on close inspection, an attempt to do in a public square what Rembrandt did on a canvas: to place something at the centre that holds a crowd's attention, and then to reveal that the crowd was the work all along.

We did not begin with the theory. We began, as the work usually does, with an accident — a job, a chance sighting, a brief so loose it was barely a brief, a playful doodle we decided to take seriously. Flock arrived in Trafalgar Square in 2007 before we had any clear idea of what we were really testing. It was only afterwards, making Strange Attractors for FACT in 2009, that we reached for the Rembrandt to explain to ourselves what had happened: that a single still figure, laid at the centre of a public space, would draw a ring of curious strangers around it and, in the act of looking, turn them into the thing worth looking at. The painting did not inspire the work. The work sent us back to the painting to find out what we had done.

What we had done, it turned out, we kept doing, at larger and larger scale, and then, abruptly, at the smallest scale we could find. Congregation took the discovery and built a machine for it: a swarm of light, a contracting circle, a figure that gathered ten thousand people in a Pittsburgh winter and then dissolved at their feet, leaving them holding nothing but their connection to one another. For six years it was the fullest answer we had to the question the work kept asking — whether the interaction of people with a work could itself be the subject of an aesthetic. And then, with People We Love, the figure at the centre disappeared entirely. No crowd, no square, no totem of light: just one person, before one screen, asked to imagine the absent face that a stranger on the screen could see and they could not. The audience was no longer the performance. The audience was now the only place the work existed at all.

That arc — from the crowd to the single viewer, from the figure at the centre to its disappearance — is the reason this body of work was more than a sequence of light shows. It was a fifteen-year argument about where a work of art is located, and who makes it. The orthodox answer is that the work is the object, and the artist makes it, and the audience receives it. KMA's work proposed something else: that the work might be the transaction — the contract between a maker who admits the artifice and an audience that agrees to complete it, and that the most interesting art might be the kind that withholds half of itself and trusts you to supply the rest.

This is, in the end, a theatrical idea rather than a cinematic one. The cinema, and the spectacle culture that descends from it, makes a different contract: trust us, none of this is constructed, sit still and believe. The theatre has always made the older bargain — we both know this is a wooden stage and a painted cloth; now let us build something together that neither of us could build alone. KMA spent fifteen years carrying that bargain out of the theatre and into the street, and then into a cathedral, and the works got their power from how completely they kept it. There were no performers to watch. There was only you, and the other people in the square, and what the four of you — or the ten thousand of you — were willing to make together out of light and attention and the permission to take part.