"Castles in the air" certainly is a fine metaphor, and reminds me of the Laputa section of Gulliver's Travels, in which Gulliver rides in a floating city of philosophers, and is treated to a myriad of viewpoints, both practical and fanciful. I wish I could remember more of this, but can't get at the book, which is packed away. Maybe Norman can help me remember, as he is familiar with Mr. Swift's work.