Idea–expression divide

The idea–expression divide or idea–expression dichotomy limits the scope of copyright protection by differentiating an idea from the expression or manifestation of that idea.

The European Union Software Directive, Article 1.2, for example, expressly excludes from copyright ideas and principles that underlie any element of a computer program, including those that underlie its interfaces. As stated by the European Court of Justice in SAS Institute Inc. v World Programming Ltd., "to accept that the functionality of a computer program can be protected by copyright would amount to making it possible to monopolise ideas, to the detriment of technological progress and industrial development."; legal scholars have described the idea-expression dichotomy as the ratio decidendi of this landmark ruling. In the United States the 1879 opinion of the Supreme Court in the case of Baker v. Selden elaborated this doctrine, holding that, while exclusive rights to the "useful art" (in this case bookkeeping) described in a book might be available by patent, only the description itself was protectable by copyright. In Harper & Row Publishers, Inc. v. Nation Enters., 471 U.S. 539, 556 (1985), the Supreme Court stated that "copyright's idea/expression dichotomy 'strike[s] a definitional balance between the First Amendment and the Copyright Act by permitting free communication of facts while still protecting an author's expression.'" (internal citation omitted). Additionally, in Mazer v. Stein, 347 U.S. 201, 217 (1954), the Supreme Court stated "Unlike a patent, a copyright gives no exclusive right to the art disclosed; protection is given only to the expression of the idea—not the idea itself."

Some of the criticism directed at "intellectual property" is based on the confusion between patents, which may confer proprietary rights in relation to general ideas and concepts per se when construed as methods, and copyrights, which cannot confer such rights.

An adventure novel provides an illustration of the concept. Copyright may subsist in the work as a whole, in the particular story or characters involved, or in any artwork contained in the book, but generally not in the idea or genre of the story. Copyright, therefore, may not subsist in the idea of a man venturing out on a quest, but may subsist in a particular story that follows that pattern. Similarly, if the methods or processes described in a work are patentable, they may be the subject of various patent claims, which may or may not be broad enough to cover other methods or processes based on the same idea. Arthur C. Clarke, for example, sufficiently described the concept of a communications satellite (a geostationary satellite used as a telecommunications relay) in a 1945 paper that it was not considered patentable in 1954 when it was developed (independently) at Bell Labs.

In the English decision of Donoghue v. Allied Newspapers Limited (1938) Ch 106, the court illustrated the concept by stating that "the person who has clothed the idea in form, whether by means of a picture, a play or a book" owns the copyright. In the Australian decision of Victoria Park Racing and Recreation Grounds Co. Ltd v. Taylor (1937) 58 CLR 479 at 498, Latham CJ used the analogy of reporting a person's fall from a bus: the first person to do so could not use the law of copyright to stop other people from announcing this fact.

Some courts have recognized that particular ideas can be expressed intelligibly only in one or a limited number of ways. The French name for this doctrine is Scènes à faire. Therefore even the expression in these circumstances is unprotected, or extremely limited to verbatim copying only. This is true in the United Kingdom and most Commonwealth countries. In the United States this is known as the merger doctrine, because the expression is considered inextricably merged with the idea. United States courts are divided on whether merger constitutes a defense to infringement or prevents copyrightability in the first place, but it is often pleaded as an affirmative defense to copyright infringement.

In August 2013, Robin Thicke, Pharrell Williams, and T.I. filed a lawsuit against the family of Marvin Gaye regarding their song "Blurred Lines"; the family had argued that "Blurred Lines" had copied the "feel" and "sound" of the Marvin Gaye song "Got to Give It Up" (which Thicke cited as an influence on the song), contradicting the idea-expression divide. In March 2015, a court ruled that, despite not even sharing the same chords, lyrics, or other copyrightable elements, that "Blurred Lines" had infringed on the copyrights of "Got to Give It Up" by copying its feel and ideas.

See also

• Feist Publications v. Rural Telephone Service
• Ho v. Taflove
• Functionality doctrine
• Stock character