Editing Idea–expression distinction (section)

==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.<ref>{{cite court |litigants=Morrissey v. Procter & Gamble Co. |vol=379 |reporter=F.2d |opinion=675 |court=1st Cir. |date=1967 }}</ref> For example, in ''Morrisey v. Proctor & Gamble'', 379 F.2d 675 (1st Cir. 1967), a set of rules for sweepstakes based on entrants' social security numbers was not copyrightable because there were only a limited number of ways to express the underlying idea of the sweepstakes instructions. In such cases the expression merges with the idea and is therefore not protected.<ref>''[https://casetext.com/case/morrissey-v-procter-gamble-company-2 Morrisey v. Proctor & Gamble]'' 379 F.2d 675 (1st Cir. 1967)</ref>

There are cases where there is very little choice about how to express some fact or idea, so a copy or close paraphrase may be unavoidable.
In this case, the "merger doctrine" comes into play.
The fact or idea and the expression are seen as merged, and the expression cannot be protected.
The merger doctrine is typically applied only to factual information or scientific theories, not to imaginative works such as plays or novels where the author has a much broader choice of expression.<ref>{{cite book |last=Fishman|first=Stephen|title=The Copyright Handbook: What Every Writer Needs to Know
 |url=https://books.google.com/books?id=oeD-6AsobjkC&pg=PA284|access-date=2012-06-19|date=2011-09-07|publisher=Nolo|isbn=978-1-4133-1617-9|page=288}}</ref>
The merger doctrine has been applied to the user interface design of computer software, where similarity between icons used by two different programs is acceptable if only a very limited number of icons would be recognizable by users, such as an image looking like a page to represent a document.{{sfn|Lai|2000|p=47}}
However, in 1994 a U.K. judge in ''Ibcos Computers v. Barclays Mercantile Finance'' [FSR 275] cast doubt on the merger doctrine, saying he was not comfortable with the idea that "if there is only one way of expressing an idea that way is not the subject of copyright."{{sfn|Lai|2000|p=45}}

[[United States federal courts|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.<ref name="LorenReese2019">{{bluebook journal |last=Loren |first=Lydia Pallas |last2=Reese |first2=R. Anthony |title=Proving Infringement: Burdens of Proof in Copyright Infringement Litigation |url=https://law.lclark.edu/live/files/28482-lcb232article5lorenpdf |volume=23:2 |year=2019 |journal=Lewis & Clark Law Review |page=621 |pin=661-65}}</ref>  Only one federal circuit, the [[United States Court of Appeals for the Ninth Circuit|Ninth Circuit]], has specifically held that merger should be considered a "defense" to [[copyright infringement]],<ref>{{cite court |litigants=Ets-Hokin v. Skyy Spirits, Inc. |vol=225 |reporter=F.3d |opinion=1068 |pinpoint=1082 |court=9th Cir. |date=2000 }}</ref> but {{as of|2019|lc=y}} this is not considered an [[affirmative defense]] as the plaintiff still carries the burden of proof that infringement occurred.<ref name="LorenReese2019"/>