Private Law Theory

ABSTRACT
Copyright is infringed if a ‘substantial part’ of a work is reproduced without authorisation. What is reproduced must be part of an expression, not an idea. But what is part of an expression, and what is an idea, can be unclear. Copyright’s effectiveness is challenged by this uncertainty: creators may be reticent to enforce their rights against unauthorised reproduction, and the public may limit the degree to which they might otherwise be legitimately inspired by songs, books, movies and videogames. In 2005, Michael Spence and Timothy Endicott responded to this uncertainty by calling for ‘controlled vagueness’ when assessing whether a substantial part of a work had been reproduced. This paper undertakes a thought experiment: can psychological, neuroscientific and other insights into creative cognition lead to ‘controlled vagueness’ in the idea-expression dichotomy? That thought experiment leads to the building block theory: that both the final artwork, play, poem, etc and its ‘building blocks’ — internally-developed, non-random and generatively-aimed choices, thoughts, and patterns – can be considered part of the expression copyright law aims to protect. In cases where the idea-expression dichotomy causes issues in determining whether infringement has occurred, this approach can add greater certainty for courts, litigants, and counsel approaching disputes about the nature and extent of unauthorised copying. It can also align the idea-expression dichotomy with the creative process, which is consistent with the notion that copyright is designed to promote, reward and recognise creativity.

Yuvaraj, Joshua, ‘Controlled Vagueness’, Creative Cognition and Copyright’s Idea-Expression Dichotomy (August 11, 2026), (2026) European Intellectual Property Review (forthcoming); University of Auckland Faculty of Law Research Paper Series 2026.