Document Type


Publication Date



Not all copying constitutes copyright infringement. Quite independent of fair use, copyright law requires that an act of copying be qualitatively and quantitatively significant enough – or “substantially similar” – for it to be actionable. Originating in the nineteenth century, and entirely the creation of courts, copyright’s requirement of “substantial similarity” has thus far received little attention as an independently meaningful normative dimension of the copyright entitlement. This Article offers a novel theory for copyright’s substantial-similarity requirement by placing it firmly at the center of the institution and its various goals and purposes. As a common-law-style device that mirrors the functioning of other areas of private law, such as tort law, substantial similarity remains an unappreciated source of flexibility and pluralism in copyright law. It allows courts to modulate the copyright entitlement’s operational robustness by altering the amount of exclusivity that a work obtains, based on different criteria, and thereby introduces “thickness” as an altogether new dimension of the entitlement. It also renders the adjudication of copyright infringement overtly pluralistic by sequencing the introduction of incommensurable values into the inquiry in a particular, reasoned order. As a mechanism of conceptual Sequencing – a multicriterion decision-making process long known to the common law – substantial similarity allows copyright law to affirm both utilitarian and personality-based considerations, while prioritizing the former over the latter systemically. Viewing copyright law through the lens of substantial similarity sheds new light on the compatibility of the institution’s goals and purposes, copyright’s structure as a “property” right, and the role of courts within its overall scheme.


Intellectual Property Law | Law