Fair use is an element of copyright law that excuses a defendant from liability for copyright infringement. Fair use exists because copyright law is intended to promote the advancement of the arts and sciences. A fair use of copyrighted matter is a use that promotes advances. The four factors judges considers in a fair use defense are: (1) the purpose and character of your use (2) the nature of the copyrighted work (3) the amount and substantiality of the portion taken, and (4) the effect of the use upon the potential market.