I remembered once, in Japan, having been to see the Gold Pavilion Temple in Kyoto and being mildly surprised at quite how well it had weathered the passage of time since it was first built in the fourteenth century. I was told it hadn't weathered well at all, and had in fact been burned to the ground twice in this century.
"So it isn't the original building?" I had asked my Japanese guide.
"But yes, of course it is," he insisted, rather surprised at my question.
"But it's been burned down?"
"Yes."
"Twice."
"Many times."
"And rebuilt."
"Of course. It is an important and historic building."
"With completely new materials."
"But of course. It was burned down."
"So how can it be the same building?"
"It is always the same building."
I had to admit to myself that this was in fact a perfectly rational point of view, it merely started from an unexpected premise. The idea of the building, the intention of it, its design, are all immutable and are the essence of the building. The intention of the original builders is what survives. The wood of which the design is constructed decays and is replaced when necessary. To be overly concerned with the original materials, which are merely sentimental souvenirs of the past, is to fail to see the living build itself.
I couldn't feel entirely comfortable with this view, because it fought against my basic Western assumptions, but I did see the point.
I don't know whether this principle lies beneath the rebuilding of the Great Wall, because I couldn't find anybody who understood the question. The rebuilt section was swarming with tourists and Coca-Cola booths and shops where you can by Great Wall T-shirts and electric pandas, and this may also have had something to do with it.