Trademark Use and the Problem of Source

This paper mediates a scholarly debate regarding the existence and desirability of a trademark use doctrine. It argues that trademark use is a predicate of liability under the Lanham Act, but those who advocate treating trademark use as a threshold question put much more weight on that concept than it can bear. Courts cannot consistently apply trademark use as a distinct element of the plaintiff's prima facie case because trademark use is not separable from the question of likelihood of confusion. Under modern trademark law, courts can determine whether a defendant has made trademark use of a plaintiff's mark only by asking whether consumers are likely to view the defendant's use as one that indicates the source of the defendant's products or services. Because such an inquiry is, by its nature, highly context-sensitive, trademark use is not a concept capable serving the limiting function advocates hope. The trademark use debate, however, reveals a fundamental problem in modern trademark law and theory. Consumer understanding, and particularly consumer understanding of source, defines virtually all of modern trademark law's boundaries. But as trademark law's dramatic expansion aptly demonstrates, these boundaries are never fixed because consumer understanding is inherently unstable, particularly with respect to an ill-defined term like source.