Schwan

Well, I have no idea what he meant, that's the whole point . As for the context... Well, the context was, more or less, the history of philosophy, starting from the ancient Greek and ending all the way in the mid XX century. I think it's more of a theoretical construct, then a technical question about modern construction methods .

Anyhow, "rational", as in something, that doesn't come from the senses, but from the mind. Rational would also mean that it's something that can't be the product of a revelation or some other mystical process, but it's something that can be easily traced to the mind and has nothing to do with intuition.

So perhaps what he meant is that the arc and the quintet are something specific to the western culture, that they are a product of a line of thought that went on for several thousand years and this is the end product, and that they couldn't be replicated in a different, independent culture? It's a wild shot, and a best one I could come up with.

Not that old, really, though he was a total egg head. I don't think he had much contact with reality, not on daily basis.