Array, 1967, pairs two panels, each over two metres high, set side by side. Across both, a sprayed ground of pale pink and violet shifts in soft, cloud-like gradations, and over it lies an unbroken lattice of ochre dots. Where the ground darkens the dots seem to rise; where it pales they settle back, so that the surface never resolves into figure and ground. The spray, which replaced thrown and spattered paint in Cohen’s work of 1966–67, let him pursue these optical effects while moving

beyond what he called merely “edge-to-edge” colour.

An array – an ordered arrangement of like elements – is a term shared by geometry and computing. The painting was made the year before curator Jasia Reichardt’s Cybernetic Serendipity opened at the ICA in London in August 1968, an exhibition Cohen visited before leaving for San Diego, and within two years he would be generating images with a computer. Here the rule is still carried out by hand: one decision, repeated across the whole surface, within which the irregularities of the sprayed ground supply variety. It is the clearest statement in this exhibition of the question that occupied Cohen for the rest of his life: what a set of instructions can produce, and where, in that process, the artist stands.