The first and third phrases come from Ezekiel 1:26 — the prophet’s vision of the divine throne: above the firmament, “the likeness of a throne, as the appearance of a sapphire stone.” Note the doubled distance: not the throne but the likeness of a throne, not sapphire but the appearance of sapphire. The German in the middle — “he sees the same blue as I do, so I do not doubt it” — sets beside the vision the problem of whether one mind’s blue is ever the same as another’s.

A blue that can only ever be described as like something, approached through layers of resemblance; and the question of whether the blue I see is the blue you see. Scripture’s blue and the philosophical blue meet on the word appearance.

Deep blue is laid in broad knife-strokes, a dark red-brown riding over it without mixing. The blue is at once depth and surface, vision and pigment — a blue shown only as the appearance of blue.