The Levels of Abstraction Problem in Patent Law

57 Pages Posted: 17 Jul 2009 Last revised: 6 Dec 2014

See all articles by Tun-Jen Chiang

Tun-Jen Chiang

George Mason University School of Law

Date Written: July 15, 2009


The concept of “invention” is fundamental to patent law. What the patentee creates as the invention, he receives as his monopoly reward. This quid pro quo suggests that patent scope is self-defining: the patentee receives whatever invention he created, and nothing else.

The quid pro quo framework breaks down, however, because “invention” means different things on the two sides of the equation. The invention that the patentee creates is an embodiment. The invention that defines monopoly scope, however, is an idea. Moreover, every patented embodiment contains many ideas, at different levels of abstraction. Courts must choose one idea to give legal protection, with important consequences. The higher the level of abstraction chosen, the more scope the patentee receives, with attendant incentive benefits and monopoly costs.

Courts that have treated idea and embodiment as a unitary invention have ignored the necessity of this choice, effectively exercising their discretion arbitrarily and silently. This Article argues instead for a legal realist approach that acknowledges discretion in determining patent scope, discards the conflicting yet absolutist rules governing this area, and determines scope based on balancing incentives and monopoly costs, with transparent analysis allowing better information to be collected and greater predictability in outcomes.

Keywords: claim construction, claim differentiation, doctrine of equivalents, insubstantial difference, Markman hearing, policy balance, vagueness

JEL Classification: K11, O34

Suggested Citation

Chiang, Tun-Jen, The Levels of Abstraction Problem in Patent Law (July 15, 2009). Northwestern University Law Review, Vol. 105, No. 3, pp. 1097-1152, Summer 2011, George Mason Law & Economics Research Paper No. 09-33, Available at SSRN:

Tun-Jen Chiang (Contact Author)

George Mason University School of Law ( email )

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