O Lords of Limit, training dark and light...

David Lewis-Williams, in The Mind in the Cave (2002). Thames & Hudson

An important reciprocality is implied by these images born of light and shadow. On the one hand, the creator of the image holds it in his or her power: a movement of the light source can cause the image to appear out of the murk; another movement causes it to disappear. The creator controls the image. On the other hand, the image holds its creator in its power: if the creator or subsequent viewer wishes the image to remain visible, he or she is obliged to maintain a posture that keeps the light source in a specific position. If the viewer tires and as a result lowers the light, the image seems to retreat into the realm behind the membrane. Perhaps more than any other Upper Palaeolithic images, these 'creatures' (creations) of light and darkness point to a complex interaction between person and spirit, artist and image, viewer and image. There was a great deal more to Upper Palaeolithic cave paintings than pictures simply to be looked at: some of the images sprang from a fundamental metaphor.