J F Martel at Aeon Magazine: What astounds us when we enter a cathedral or contemplate a Mark Rothko is not merely the finished form of these works but the strange transformation each embodies. I know the stone to be impossibly heavy, yet I see it suspended as though lighter than air; I see the strokes of paint, yet the colour field feels all the more solid for them. Aside from this, it is the gratuitous contingency of the building and the paint…