have considered and ruled upon the fair use doctrine
over and over again, no real definition of the concept has ever emerged.
Indeed, since the doctrine is an equitable rule of reason, no generally
applicable definition is possible, and each case raising the question
must be decided on its own facts. On the other hand, the courts have
evolved a set of criteria which, though in no case definitive or
determinative, provide some gauge for balancing the equities. These
criteria have been stated in various ways, but essentially they can all
be reduced to the four standards which have been adopted in section 107:
"(1) the purpose and character of the use, including whether such use is
of a commercial nature or is for non-profit educational purposes; (2)
the nature of the copyrighted work; (3) the amount and substantiality of
the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the
copyrighted work."

These criteria are relevant in determining whether the basic doctrine of
fair use, as stated in the first sentence of section 107, applies in a
particular case: "Notwithstanding the provisions of section 106, the
fair use of a copyrighted work, including such use by reproduction in
copies or phonorecords or by any other means specified by that section,
for purposes such as criticism, comment, news reporting, teaching
(including multiple copies for classroom use), scholarship, or research,
is not an infringement of copyright."

The specific wording of section 107 as it now stands is the result of a
process of accretion, resulting from the long controversy over the
related problems of fair use and the reproduction (mostly by
photocopying) of copyrighted material for educational and scholarly
purposes. For example, the reference to fair use--"by reproduction in
copies or phonorecords or by any other means"--is mainly intended to make
clear that the doctrine has as much application to photocopying and
taping as to older forms of use; it is not intended to give these kinds
of reproduction any special status under the fair use provision or to
sanction any reproduction beyond the normal and reasonable limits of
fair use. Similarly, the newly-added reference to "multiple copies for
classroom use" is a recognition that, under the proper circumstances of
fairness, the doctrine can be applied to reproductions of multiple
copies for the members of a class.