quoted from Calvino's Hermit in Paris:

Among the Invisible Cities there is one on stilts, and its inhabitants watch their own absence from on high. Maybe to understand who I am I have to observe a point where I could be but am not. Like an early photographer who poses in front of the camera and then runs to press the switch, photographing the spot where he could have been but isn't. Perhaps that is the way the dead observe the living, a mixture of interest and incomprehension.

As posted here on this fantastic blog.