“So this isn’t the original building?” Adams asked.
“But yes, of course it is.”
“But it’s been burned down?”
“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,” Adams wrote. The essence of a building is its design, the intention of the builder. The materials may decay and be replaced, but these are only instantiations of a persistent idea. “I couldn’t feel entirely comfortable with this view, because it fought against my basic Western assumptions,” Adams wrote, “but I did see the point.”
That's from Adams' book Last Chance to See. John Locke asked: If I keep patching holes in my sock until none of the original material remains, is it the same sock?