The idea–expression distinction or idea–expression dichotomy limits the scope of copyright protection by differentiating an idea from the expression or manifestation of that idea. Unlike patents, which may confer proprietary rights in relation to general ideas and concepts per se when construed as methods, copyrights 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 in a 1945 paper that it was not considered patentable in 1954 when it was developed at Bell Labs.
Legal origins and status
In the United States, the doctrine originated from the 1879 Supreme Court case of Baker v. Selden. The Supreme Court held in Selden that, while exclusive rights to the "useful arts" described in a book might be available by patent, only the description itself was protectable by copyright. In later cases, the Supreme Court has stated that "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," and that "copyright's idea/expression dichotomy 'strike a definitional balance between the First Amendment and the Copyright Act by permitting free communication of facts while still protecting an author's expression.'" In the English decision of Donoghue v. Allied Newspapers Limited 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 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. Today, Article 1.2 of the European Union Software Directive 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 monopolize ideas, to the detriment of technological progress and industrial development."
''Scènes à faire''
Some courts have recognized that particular ideas can be expressed effectively only by using certain elements or background. 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 it is recognized that certain background elements are universal or at least commonplace in some types of work. For example, in Walker v. Time Life Films, Inc., 784 F.2d 44, the Second Circuit said that in a film about cops in the South Bronx it was inevitable that the scenery would include drunks, stripped cars, prostitutes, and rats. In Gates Rubber Co. v. Bando Chemical Industries, Ltd., 9 F.3d 823, the Tenth Circuit held that hardware standards and mechanical specifications, software standards and compatibility requirements, computer manufacturer design standards, target industry practices and demands, and computer industry programming practices were unprotectable scènes à faire for computer programs. The principle must have a limit, however, so that something is outside the scènes à faire doctrine for South Bronx movies. Perhaps, cockroaches, gangs, and muggings are also part of the South Bronx scène à faire, but further similarity such as the film having as characters "a slumlord with a heart of gold and a policeman who is a Zen Buddhist and lives in a garage surely goes beyond the South Bronx scène à faire. There must be some expression possible even in a cliche-ridden genre."
Merger doctrine
A broader but related concept is the merger doctrine. Some ideas can be expressed intelligibly only in one or a limited number of ways. The rules of a game provide an example. In such cases the expression merges with the idea and is therefore not protected. United States courts are divided on whether merger prevents copyrightability in the first place, or should instead be considered when determining if the defendant copied protected expression. Only one federal circuit, the Ninth Circuit, has specifically held that merger should be considered a "defense" to copyright infringement, but as of 2019 this is not considered an affirmative defense as the plaintiff still carries the burden of proof that infringement occurred.
