It is significant, as William Vaughan remarks in his introduction to Borsch-Supan's catalogue, that churches never appear in Friedrich's work except in the distance, as unreal visions, or as ruins. The visible Church is dead, only the invisible Church, in the heart or revealed through Nature, is alive. This is part of Friedrich's Pietist heritage, a personal religion that refuses all outward forms, all doctrine. To put a landscape on an altar is an aggressive act, as destructive of the old forms as it is creative of a new sensibility.