Annunciation Triptych (Merode Altarpiece) (Workshop of Robert Campin, The Cloisters)

Open the right wing of this small triptych and the scene looks almost too ordinary to matter: a carpenter at his bench, tools scattered around him, sunlight through a shuttered window. Only on close looking does an odd detail draw the eye. Twice over, the carpenter is shown finishing a small wooden mousetrap.

The Metropolitan Museum's own reading of the panel identifies the carpenter as Joseph, and reads his mousetraps through a specific piece of theology going back to Augustine. In this account, humanity had been ensnared by the devil the way an animal is caught by bait, and God's answer was to become bait himself: the Incarnation, God taking on ordinary human flesh in a Nazareth household, was the trap set to catch the trapper. Christ's humanity is the visible bait; his divinity is the trap's working part, hidden until it is too late for whatever it has caught.

It is a strange way to picture the central claim of Christian theology, mundane carpentry tools standing in for a cosmic reversal, and that strangeness is close to the point. The painters of this triptych were not illustrating a creed recited aloud in church. They found the doctrine already sitting inside an ordinary carpenter's workshop, hidden in plain sight the way the Incarnation itself, in this reading, hides God inside an ordinary human life.

Most surviving altarpieces of this scale and ambition were built for churches: raised on public altars, seen by whole congregations, paid for by guilds or bishops. This one was not. Its scale, barely two feet wide when opened, and its two donor portraits kneeling in the left wing identify it instead as a private commission, made for the wall of an ordinary well off household in the southern Netherlands sometime around 1427 to 1432.

That distinction changes what the painting is doing. A church altarpiece has to hold a crowd's attention from a distance and survive weekly repetition. A domestic devotional panel like this one rewards a single person standing close, returning to it daily, noticing something new each time, exactly the kind of looking that eventually turns up two small mousetraps on a carpenter's bench. The Virgin's private domestic interior in the central panel, down to the folded towel and the kettle on the fire, was painted for viewers who lived in rooms very much like it themselves.

The Metropolitan Museum of Art has held the triptych since 1956, acquired for The Cloisters, its medieval branch built specifically to give paintings like this one a setting closer to the intimate devotional space they were made for than a conventional museum gallery could offer.