JM -
Pei seems to be making two separate points - first, that only Time can give us a proper perspective on modern work and second, that Kahn consciously embued his work with spirit and permanence. I disagree with the first point, i.e. I think time gives us ONE perspective, but just one among many such perspectives and not necessarily the "proper" one. But I think his second point is crucial, and may have a parallel to golf course architecture. It is the architect's CHOICE whether to embue a golf course with spirit and permanence (or at least to try to). And the only aspect of modern work that Time cannot change is that -- the artist's INTENTION.
Personally, I've never played a golf course where I thought the architect did not know what he was doing; I've never played a badly designed golf course in this sense. But I've played many where it was clear that the architect's intention was not to create a course embued with a sense of spirit and permanence. How important is that, or should it be? I don't know.
Some of the oldest courses, of course, get a free pass on the permanence part, in a proof-is-in-the-pudding sort of way...
Peter