No one is sure what Blake meant by mentioning ‘dark, Satanic mills’ as part of what Jesus would have seen and moved among, but the candidates include early industrial sites, Druidic temples and (I’m afraid) Anglican parish churches. The point, though, is that we are being asked to imagine that the incarnate God moved and worked even in the middle of the cruelty, hypocrisy and exploitation that are an inseparable part of every human community’s history. ‘Jerusalem’ is being built, even while all the signs in society around us seem to negate the vision.
What we need is the rekindling of desire – the sheer passionate longing to see a social order at which the Holy Lamb of God might look without heartbreak. Arrows of desire; the courage and endurance of mental fight; the struggle to keep this imagination alive and burning – this is what we pray for. The poem looks back to an imaginary past and forward to an imagined future, but at its heart is the question: ‘do you truly want to live in Jerusalem? Because if you do, you need to remember that it is always already here and now; because even where justice and love seem to be defeated, the Holy Lamb of God is present.’
— Rowan Williams, from Candles in the Dark