In this case, navigating through a body of knowledge involves being able to yaw, pitch, and roll as if you were flying a helicopter, a rather different set of skills than knowing how to turn pages or to use an index or table of contents. It's hard to communicate, in print, the look and feel of entering virtual worlds. Having tried, however, to make strange things familiar, it might be instructive at this point to make some familiar things strange. Text simulates thought. It's an artifact, representing with its own particular richness and its own unique limitations the ineffably complex workings of the human mind going about its business of making sense of things.
Text is a version of the thought that the text represents.
It's a working model of what's on our minds. Text is virtual thought. Now consider this. A word processor creates virtual paper. The technology, in fact, fills a new medium with an old content.