Citation from "As We May Think"

Most of the Memex contents are purchased on microfilm ready for insertion. Books of all sorts, pictures, current periodicals, newspapers, are thus obtained and dropped into place. Business correspondence takes the same path.

This compares well to the scientific literature, encyclopedia, dictionaries, etc. which are all becoming available electronically.

The reason why Bush proposed Memex is very similar to the reasons why information is becoming available electronically and why so many people put effort into world-wide information systems: the explosion of (scientific) information makes it impossible for any individual to keep track of all developments, even in a narrow field of interest. When all scientific literature would be available through the World Wide Web, a search for all documents about a certain topic could be performed by the computer while we are asleep. (Such a search would require more elaborative filtering of WWW pages than simply giving a few keywords to Alta Vista or another search engine and retrieving the resulting documents.)