Baker v. Selden 101 U.S. 99 (1879) was a decision by the Supreme Court of the United States on the existence of copyright and how to distinguish between idea and expression. Seal of the Supreme Court The Supreme Court of the United States is the highest federal court in the United States of America. ...

Charles Selden obtained copyright in a book he wrote called "Selden's Condensed Ledger, or Book-keeping Simplified". In it the book described a system of book-keeping. In the following years Selden made several other books, improving on the inital system. Baker produced a book describing a very similar system with only slight variations.

The Court focused on the distinction between the means and the ends of the book. The purpose of the book was seen as the "idea" of the book and cannot be copyrighted. However, the particular means of achieving that purpose was an expression and thus can be copyrighted. As Baker's book was not similar enough to be a reproduction then it does not violate Selden's copyright.