IP Compendium

Notes on Canadian intellectual property law

User Tools

Site Tools


Idea-Expression Dichotomy

A long-held principle of copyright law is that an “idea” cannot be copyrighted, and that only the “expression” of an idea is subject to copyright law. This concept is closely related to the concepts of originality (since only the originality of expression is protected, and not originality of idea) and fixation (expression being the necessary consequence of fixation). The distinction between idea and expression is often referred to as the “idea-expression dichotomy” or the “idea-expression divide”. In this context, the word “idea” also often extends to “facts” (i.e. one cannot generally copyright facts).

History and justification

The principle that ideas are not subject to copyright protection is as old as copyright law itself. The origins of the doctrine are reflected in the fundamental conception of the purpose of copyright law and the “balance” to be struck between author's rights and the public interest. An version of this principle was provided by Lord Mansfield as early as 1785 in Sayre v Moore:1

We must take care to guard against two extremes equally prejudicial: the one that men of ability, who have employed their time for the service of the community may not be deprived of their just merits and reward for their ingenuity and labour; the other that the world may not be deprived of improvements nor the progress of the arts be retarded.

From the utilitarian/instrumentalist view, the idea/expression dichotomy is derived from this underlying purpose of copyright, by providing public access to new works and new ideas while providing incentives for creativity.2

From a Lockean perspective (i.e. as the “labour theory of property”), the idea-expression dichotomy is a manifestation of the principle that one is only entitled to the fruits of their labour. In this sense, ideas are “free” since they are a “public good” available to all. One is only entitled to property over what they have created out of the public good, or in copyright terms, what they have expressed in material form.3 Professor Walter Copinger provides such an account in his seminal treatise on copyright law, first published in 1870:4

Ideas, being neither capable of a visible possession nor of sustaining any one of the qualities or incidents of property, inasmuch as they have no bounds whatever, cannot be the subject of property. Their whole existence is in the mind alone; incapable of any other mode of acquisition or enjoyment than by mental possession or apprehension, safe and invulnerable from their own immateriality, no trespass can reach, no tort affect, no fraud or violence diminish or damage them. They are of a nature too unsubstantial, too evanescent, to be the subject of proprietary rights.

When, however, any material has embodied those ideas, then the ideas, through that corporiety, can be recognised as a species of property by the common law. The claim is not to ideas, but to the order of words, and this order has a marked identity and a permanent endurance. The order of each man's words is as singular as his countenance, and although, if two authors composed originally with the same order of words, each would have a property therein, still the probability of such an occurrence is less than that there should be two countenances that could not be discriminated. The permanent endurance of words is obvious by comparing the words of ancient authors with other works of their day; the vigour of the words is unabated, though other works have mostly perished. It is true that property in the order of words is a mental abstraction, but so are many other kinds of property; for instance, the property in a stream of water, which is not in any of the atoms of the water, but only in the flow of the stream. The right to the stream is not the less a right of property, either because it generally belongs to the riparian proprietor, or because the remedy for a violation of the right is by action on the ease, instead of detinue or trover. [Citations omitted.]


United States

Baker v Selden,5 an 1879 decision of the United States Supreme Court, is an oft-cited example of a court enshrining the distinction between idea and expression in copyright law. The case involved a system of book-keeping, which was described in the book Selden's Condensed Ledger, or Book-keeping Simplified. The book primarily consisted of forms for the book-keeping system, with some explanatory notes and an introduction. The defendant, who produced a book describing a similar system, was sued for copyright infringement but argued that the plaintiff did not have any copyright over the system itself. The Court held that while copyright protection extended to the original book itself, it did not protect the underlying system described by the book:6

There is no doubt that a work on the subject of book-keeping, though only explanatory of well-known systems, may be the subject of a copyright; but, then, it is claimed only as a book. […] But there is a clear distinction between the book, as such, and the art which it is intended to illustrate. The mere statement of the proposition is so evident, that it requires hardly any argument to support it. The same distinction may be predicated of every other art […] but no one would contend that the copyright of the treatise would give the exclusive right to the art or manufacture described therein. The copyright of the book, if not pirated from other works, would be valid without regard to the novelty, or want of novelty, of its subject matter. The novelty of the art or thing described or explained has nothing to do with the validity of the copyright. To give the author of the book an exclusive property in the art described therein, when no examination of its novelty has ever been officially made, would be a surprise and a fraud upon the public. That is the province of letters-patent, not of copyright. […]

The very object of publishing a book on science or the useful arts is to communicate to the world the useful knowledge which it contains. But this object would be frustrated if the knowledge could not be used without incurring the guilt of piracy of the book. And where the art it teaches cannot be used without employing the methods and diagrams used to illustrate the book, or such as are similar to them, such methods and diagrams are to be considered as necessary incidents to the art, and given therewith to the public; not given for the purpose of publication in other works explanatory of the art, but for the purpose of practical application.

The Court thus drew a distinction between an idea (in this case a system for book-keeping) and the expression of the idea (the book-keeping forms and explanatory notes). The decision also provides a further carve-out from copyright protection - expressions that are “necessary incidents to the art” are not protected, as it would be tantamount to extending copyright protection to the underlying idea (see the discussion on merger of idea and expression below). While Baker v Selden firmly established the idea/expression distinction in US copyright law, its application has not been without difficulty or controversy, a debate that has been brought back to life with the advent of computer software.7


Despite differences in copyright legislation across the various common law jurisdictions, the idea/expression distinction has seen nearly universal application.8

English jurisprudence adopted the distinction between idea and expression as posited by Baker v Selden in Hollinrake v Truswell.9 The English Court of Appeal ruled that a “sleeve chart” made of a piece of arm-shaped cardboard with printed words such as “top curve line; under curve line; under arm curves; etc.” used for the purpose of measuring sleeves was not subject to copyright because the sleeve chart was a tool or machine necessary to operate the system. Granting copyright to the sleeve chart would grant a monopoly over the system. In so deciding, the Court expressly adopted the Baker v Selden rationale:

Copyright, however, does not extend to ideas, or schemes, or systems, or methods; it is confined to their expression; and if their expression is not copied the copyright is not infringed. The case of Baker v Selden, already referred to, illustrates this quite well.10

In Canada, an early authority for the idea/expression divide is found in Deeks v Wells, in which the Ontario Court of Appeal adopted Professor Copinger's statement of principle (above) and found that there could be no copyright in the facts of history or in their chronological sequence:11

There can be no copyright in ideas or information, and it is no infringement of copyright to adopt the ideas of another or to publish information derived from another, provided there is no copying of the language in which those ideas have, or that information has, been previously embodied.12

A more frequently cited authority in Canada is that of Thorson P. in Moreau v St Vincent:13

It is, I think, an elementary principle of copyright law that an author has no copyright in ideas but only in his expression of them. The law of copyright does not give him any monopoly in the use of the ideas with which he deals or any property in them, even if they are original. His copyright is confined to the literary work in which he expressed them. The ideas are public property, the literary work is his own. Everyone may freely adopt and use the ideas but no one may copy his literary work without his consent.

After stating this principle, Thorson P. held that a system of awarding prizes in a magazine contest was not an expression subject to copyright protection, although the receipts, questionnaires, and instructions were (however these were not copied in this case).

Idea/expression and originality

The distinction between idea and expression is also closely related to the concept of originality. Since copyright subsists only in original works, it is logical to ask: “the originality of what?” Copyright law answers this question by allowing only original expression to be protected. A clear distinction between originality of ideas and originality of expression is drawn in University of London Press Ltd v University Tutorial Press Ltd 14 by Peterson J, dealing with the question of whether examination papers in mathematics were subject to copyright protection:

The word “original” does not in this connection mean that the work must be the expression of original or inventive thought. Copyright Acts are not concerned with the originality of ideas, but with the expression of thought, and, in the case of “literary work,” with the expression of thought in print or writing. The originality which is required relates to the expression of the thought. But the Act does not require that the expression must be in an original or novel form, but that the work must not be copied from another work - that it should originate from the author.

[…] It was said, however, that [the professors who set the examinations] drew upon the stock of knowledge common to mathematicians, and that the time spent in producing the questions was small. These cannot be tests for determining whether copyright exists. If an author, for purposes of copyright, must not draw on the stock of knowledge which is common to himself and others who are students of the same branch of learning, only those historians who discovered fresh historical facts could acquire copyright for their works. […]


A “natural corollary of the idea/expression distinction”15 is the “merger doctrine”, which posits that where an idea and its expression are so inextricable that the idea can only be expressed in one or a very limited number of ways, there can be no copyright protection even for the expression. Were copyright to be granted to such a “merged” expression, it would amount to a grant of monopoly on the underlying idea itself.

This doctrine was alluded to by the Court in Baker v Selden, in which the Court stated that expressions “considered as necessary incidents to the art” must be “given to the public”.16 American courts subsequently developed and refined this doctrine into a more complete formulation. For example, in Morrissey v Procter & Gamble Co,17 the Court of Appeals for the First Circuit wrote:

When the uncopyrightable subject matter is very narrow, so that “the topic necessarily requires,” if not only one form of expression, at best only a limited number, to permit copyrighting would mean that a party or parties, by copyrighting a mere handful of forms, could exhaust all possibilities of future use of the substance. In such circumstances it does not seem accurate to say that any particular form of expression comes from the subject matter. However, it is necessary to say that the subject matter would be appropriated by permitting the copyrighting of its expression. We cannot recognize copyright as a game of chess in which the public can be checkmated.18

The merger doctrine has been accepted in Canadian jurisprudence, although not with much frequency.19 Delrina Corp v Triolet Systems Inc20 is an instance in which a Canadian court accepted the merger doctrine, in the context of computer software. The Ontario Court of Appeal noted that:

Clearly, if there is only one or a very limited number of ways to achieve a particular result in a computer program, to hold that that way or ways are protectable by copyright could give the copyright holder a monopoly on the idea or function itself.21

Further reading

  • Allen Rosen, “Reconsidering the Idea/Expression Dichotomy” (1992) 26 UBC L Rev 263. (HeinOnline)
  • Jessica Litman, “The Public Domain” (1990) 39 Emory LJ 965. (HeinOnline)
  • Carys J Craig, “Locke, Labour and Limiting the Author's Right: A Warning against a Lockean Approach to Copyright Law” (2002), 28 Queen's LJ 1. (SSRN)
  • Abraham Drassinower, “A Rights-Based View of the Idea Expression Dichotomy in Copyright Law” (2003) 16 Canadian J L & Jurisprudence 3. (SSRN)
  • Dale P Olson, “The Uneasy Legacy of Baker v Selden” (1998) 43 SD L Rev 604. (HeinOnline)

1 (1785) 102 ER 139 at 140.
2 Allen Rosen, “Reconsidering the Idea/Expression Dichotomy” (1992) 26 UBC L Rev 263.
3 Jessica Litman, “The Public Domain” (1990) 39 Emory LJ 965.
4 Walter Arthur Copinger, The Law of Copyright (London: Stevens and Haynes, 1870) at 5.
5 101 US 99 (1879).
6 Baker v Selden at 102-4.
7 See e.g. Dale P Olson, “The Uneasy Legacy of Baker v Selden” (1998) 43 SD L Rev 604; Pamela Samuelson, “Why Copyright Excludes Systems and Processes from the Scope of its Protection” (2006) 85 Tex LR 1921.
8 Delrina Corp v Triolet Systems Inc (2002), 58 OR (3d) 339 (Ont CA) at para 33 (“It is a fundamental feature of the copyright law in all three countries [referring to Canada, England, and the U.S.] that it protects only original expression. It does not protect the idea underlying the expression.”).
9 [1894] 3 Ch 420 (CA).
10 [1894] 3 Ch 420 at 425, per Lindley, LE; see also ibid at 428 (“No doubt one may have copyright in the description of an art; but having described it, you give it to the public for their use; and there is a clear distinction between the book which describes it, and the art or mechanical device which is described. I agree with what is said in an American case of Baker v Selden […]”, per Davey, LJ.).
11 [1931] 4 DLR 533 (Ont CA).
12 Ibid, quoting FE Skone James, Copinger on the Law of Copyright, 6th ed (London: Sweet & Maxwell, 1927) at 31, citing Hollinrake v Truswell, [1894] 3 Ch 420, Walter v Stenkopff, [1892] 3 Ch 489, Chilton v Progress Printing & Publishing Co, [1895] 2 Ch 29, and other cases.
13 [1950] Ex CR 198 at 203, cited with approval in Cuisenaire v South West Imports Limited, [1969] SCR 208 at 211. See also Fletcher v Polka Dot Fabrics Ltd (1993), 51 CPR (3d) 241 at 246-9 (Ont Gen Div).
14 [1916] 2 Ch 601.
15 Delrina Corp v Triolet Systems Inc (2002), 58 OR (3d) 339 at para 52 (Ont CA).
16 Baker v Selden at 102-4.
17 379 F.2d 675 (1st Cir, 1967).
18 Ibid at 678-9.
19 See e.g. Promotions Atlantiques Inc v Hardcraft Industries Ltd (1987), 17 CPR (3d) 552 (Fed TD), citing Morrissey v Procter & Gamble Co, supra.
20 (2002), 58 OR (3d) 339 (Ont CA).
21 Delrina, ibid at para 52. C.f. Apple Computer Inc v Mackintosh Computers Ltd (1986), 10 CPR (3d) 1 (FCTD), aff'd (1988) 18 CPR (3d) 129 (FCA), aff'd [1990] 2 SCR 209, where Reed J. rejected the merger argument for a computer program in general terms; Ibcos Computer Ltd v Barclays Mercantile Highland Finance Ltd, [1994] FSR 275, where Jacob J. criticized the merger doctrine as it applied to computer software, stating that “it is a question of degree”.
copyright/idea_expression.txt · Last modified: 2015/08/18 21:18 by KPS