Idea-Expression Dichotomy means that ideas per se are not protectable under copyright laws, but expressions of these ideas are. Accordingly, an idea that is not manifested into a specific, particular arrangement of words, designs, or other forms may not be protected under copyright laws. This long-standing principle of copyright law is affirmed by the Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPs), Article 9(2):
“Copyright protection shall extend to expressions and not to ideas, procedures, methods of operation or mathematical concepts as such.”
Examples of Idea-Expression Dichotomy:
If a film based on a gangster from Mumbai is made, it does not prevent other filmmakers from making a film having a similar plot. Recently, in India, Scam 1992 (directed by Hansal Mehta, starring Pratik Gandhi) and The Big Bull (directed by Kookie Gulati, starring Abhishek Bachchan) were released. Both the motion pictures were based on Harshad Mehta’s story. Even though the idea/plot of these films was similar, their expressions were unique.
An Indian landmark decision regarding idea-expression dichotomy is R.G Anand v. M/S. Delux Films & Ors. (1978) . This case stated that mere idea does not get copyright protection. However, the earliest case regarding the idea-expression dichotomy was the U.S. Supreme Court decision in the case of Baker v. Selden (1879) . In this case, protection was awarded to the expression made by Selden in his 6 books and not the system of book-keeping mentioned in his books.
Idea-Expression Dichotomy and Copyright infringement
The concept of idea-expression dichotomy is pertinent in deciding the infringement of any copyright-protected work. The U.K House of Lords decision in Designers Guild Ltd v. Russell Williams (Textiles) Ltd   emphasized that, in cases of artistic copyright, the more abstract and simple the copied idea, the less likely it is to constitute a substantial part. In this case, the plaintiff’s employee created an original design for dress fabric. The defendant, having seen the plaintiff’s fabric, produced a very similar design for its fabric and claimed that it had copied merely the “idea” and not its “expression”. However, the judge decided that Defendant’s design contained a substantial part of Plaintiff’s design amounting to infringement.
Further, courts across jurisdictions have stated that copyright does not subsist in style , in news , in history, historical incidents, or facts , in scientific principles or descriptions of art , in mere principles or schemes , in methods of operation  and in general ideas, e.g. for entertainment. . This enables us in understanding as to what amounts to ideas, which are not protected under copyright laws.
Idea-Expression Dichotomy encourages creativity and prevents monopoly in the creative industry. It allows expressions portraying different perspectives over similar ideas. Even though ideas are not protectable under the law of copyrights, ideas may be protected under the law of confidence. Accordingly, copying ideas may amount to a breach of confidentiality.
 R.G Anand v. M/S. Delux Films & Ors., 1978 AIR 1613; 1979 SCR (1) 218; 1978 SCC (4) 118.
 Baker v. Selden, 101 U.S. 99 (1879).
 Designers Guild Ltd v. Russell Williams (Textiles) Ltd  1 W.L.R. 2416.
 Norowzian v. Arks Ltd (No. 2)  E.M.L.R. 67 (U.K.: Court of Appeal.
 Wainwright Securities Inc. v. Wall St. Transcript Corp., 558 F.2d 91 (U.S. Court of Appeals, 2d Cir. 1977).
 Hoehling v. Universal City Studios Inc., 618 F.2d 97 (U.S.: Court of Appeals, 2nd Cir., 1980).
 Baker v. Selden, 101 U.S. 99.
 Borden v. General Motors Corp., 28 F. Supp. 330 (U.S.: District Court, New York, 1939).
 Lotus Development Corp. v. Borland International, Inc., 49 F.3d 807 (U.S.: Court of Appeals, 1st Cir., 1995), aff’d (4:4) 116 S. Ct. 804 (U.S.: Supreme Court, 1996).
 Green v. Broadcasting Corporation of New Zealand  3 N.Z.L.R. 18 (New Zealand: Judicial Committee of the Privy Council).