Great Works: Icon of the Heavenly Ladder of St John Klimakos

Late 12th century, anonymous, Holy Monastery of St Catherine, Sinai

A board game gives a god's eye's view. The players sit around the playing area and look down on it, like the Olympians in Homer, as they survey the battlefields of Troy. They have no visibility problems of the kind that arise in life down on the ground – or in most pictures. All is displayed for them, as in a map or a diagram.

Board game players are not absolute masters, of course. They can move their pieces around, but they must obey the rules of the game and suffer the vicissitudes of the dice. They may lose. They may get frantically emotionally involved in the play. Still, and unlike Homer's gods, they never bodily descend into the action. They stay at a remove from the cockpit or racetrack beneath their gaze. Board games are an exercise in passion at a distance.

The origins of Snakes and Ladders are obscure. Like many of our apparently traditional institutions, it isn't all that old. The now "classic" up-and-down race game seems to have been introduced into Britain in the late 19th century by the game-makers John Jaques. It didn't arrive in the United States until the mid-20th century.

But the inspiration for these Western amusements was a much more ancient Indian game, using a similar but more complicated layout, and with each of the climbs and slides specifically moralised. Dating back to the second century, it was called Paramapada Sopanam, The Ladder to Salvation.

Despite the strong visual and conceptual echoes, no historical connection is to be traced in either direction to the Icon of the Heavenly Ladder of St John Klimakos. This John was the abbot of a monastery in Sinai, who wrote a book about salvation. The image here, based on his text, was made in Sinai or Constantinople. It shows John himself leading a troupe of monks up a 30-runged ladder from the earth to the heaven.

At the top, they are welcomed by Jesus. Along their spiritual journey they are watched and prayed for by (above) a group of angels and (below) a group of more monks. But these supporters can do nothing to intervene as the monks are continuously assailed by demons. These skinny black silhouetted figures float and walk in the air around them, strike cocky and insouciant poses, and knock, pluck and pull them off balance and off ladder.

The lost are then tipped down into a dark hole to hell at the bottom. But their fellow pilgrims don't turn a sympathetic look towards their damned brothers as they drop, but keep all eyes on the prize. They need to. The long Heavenly Ladder may be a symbol, but it's well chosen, with a good practical sense of what ladders are like – handy and perilous, a means of gradual ascent and something you can easily fall off. Game-wise, it works as both a ladder and a snake.

And the icon's likeness to the modern or ancient board game is not to be shrugged off as a coincidence. There is a common visual language. The icon's viewer may not literally look down on it, but as in Snakes and Ladders, the essential spatial relationship is a progression from bottom to top. Every figure is a cut-out piece in the game. We survey these souls' fates with both concern and detachment. It wouldn't be hard to translate this icon into a playable game with dice.

The spirit of play, almost of comedy, already informs it. The grave metaphysical subject is displayed with a diagrammatic, game-like clarity. There is the beautifully neat device of setting the ladder at a diagonal that runs from bottom left to top right corners, perfectly bisecting the picture area. There's the way the lost monks flip vertically from their perches, like metal pieces knocked down in a shooting gallery. Up/down, either/or, saved/lost: in this game there is no middle ground.

'The Icon of the Heavenly Ladder of St John Klimakos' is currently on show in Byzantium 330-1453 at the Royal Academy, London W1 (0870 848 8484), to 22 March