WE HAVE ALWAYS DEPENDED ON THE PRODUCTIVE THOUGHTS OF OUR READERS:

Is There "Hope" for Shepard Fairey?: How does fair-use law work, anyway? (Tim Wu, Oct. 21, 2009, Slate)

[T]ake a look at what has been declared fair use by courts or legislatures. They include:

* Quotations of reasonable length
* Parody (but not satire)
* Use in news reporting
* Time-shifting (recording TV for later viewing)
* Thumbnailing (resizing) for image search engines
* Reverse-engineering for a new operating platform (figuring out what you need to do to write a game that works on a Sony Playstation)
* Limited copying for classroom or educational use

What do these things have in common? One answer, borne out by the quotation example, is that fair use aids secondary creativity, or creativity that builds on an original. "The use must be of a character that serves the copyright objective of stimulating productive thought and public instruction," Judge Pierre Leval of the federal appeals court wrote in a famous article.