Colin McCahon was New Zealand’s greatest modern painter. He is also one of the most radical and challenging painters to emerge from Australasia in the 20th century.

Faith, doubt and the power of art were McCahon’s constant concerns. Beginning in the 1940s with religious scenes set in the New Zealand landscape, McCahon evolved an increasingly distinctive visual language for the life and trials of the spirit. In 'Teaching aids 2 (July)', this spiritual sign language is at its most stark and mysterious.

As the title suggests, this is a painting about art’s power as a guide – an aid to understanding matters of life and death. On a series of what look like humble school blackboards, a lesson plays out. Numbers accumulate up to 14, evoking the Christian stations of the cross, while the white lines, floating in the blackness, become luminous crucifixions.