The Fair Use Doctrine allows and even encourages use of copyrighted works for socially beneficial activities such as teaching, learning, and scholarship. Courts consider four factors in deciding whether a use is Fair Use or an infringement:
- Purpose of the Use (learning, commentary, criticism OR commercial);
- Nature of the Publication (factual OR creative);
- Amount and Substantiality of the Whole (small OR substantial);
- Effect on the Market (has no affect OR replaces a sale).
Most courts consider the first and fourth factors to be more important, but all four factors should be taken into account, and it is only after considering all of them that one can conclude if a specific use of copyrighted work is fair or not. Each case is distinct, and other combinations of these factors can also be considered fair; it all depends on the specific circumstances. The Fair Use doctrine is deliberately flexible to permit uses that may "promote the progress of science and useful arts".
There is a wealth of great information available from the Columbia University Copyright Advisory Office. Stanford University Libraries also maintains a very useful Copyright and Fair Use website. You may be interested in the Copyright Office's Circular 21, Reproductions of Copyrighted Works by Educators and Librarians.
Hofstra University has adopted a Fair Use Checklist to assist faculty in making fair use decisions.