When I was learning to write in my teens, it seemed to me that paper was a prison. Four walls, right? And the ideas were constantly trying to escape. What is a parenthesis but an idea trying to escape? What is a footnote but an idea that tried — that jumped off the cliff? Because paper enforces single sequence — and there’s no room for digression — it imposes a particular kind of order in the very nature of the structure.

— Ted Nelson, demonstration of Xanadu Space