The fair use doctrine is at once the most significant and the most problematic qualification of the copyright owner's right to exclusivity. An affirmative defense against copyright liability, the fair use doctrine legitimates certain unauthorized reproductions of copyrighted materials that would otherwise be regarded as copyright infringements. Notwithstanding its importance, “fair use” continues to be “the most troublesome [doctrine] in the whole law of copyright.” Throughout its long history, neither courts nor legislatures have provided a useful definition of “fair use” nor have they adumbrated its objectjves. Since the doctrine's inception over two and a half centuries ago, courts and legislatures have attempted to formulate, explicate, refine, and revamp the fair use doctrine. Generally, these efforts have proven unfruitful. At best, they have resulted in various formulations of how to approach fair use questions that offer courts and users of copyrighted works scant guidance on how fair use should be recognized. All this would not have been of grave concern had judges shared a common understanding of fair use or of the principles that should guide them in deciding fair use cases. The problem is that they do not. Rather, the case law reflects wdely divergent notions of the concept of fair use. The lack of consensus is best witnessed in the multiple reversals and divided courts that have become the hallmark of fair use litigation.