G 1/23: Reductio Ad Absurdum

The reductio ad absurdum logical argument is a well known way of disproving an initial statement by showing that it leads to an absurd conclusion. If the initial statement is either true or false, the argument when properly applied inevitably leads to the conclusion that the opposite must be true. A well known application of the argument is the proof that there are infinitely many prime numbers, which dates back to ancient Greek times and is attributed to Euclid. The proof starts by assuming there are not infinitely many prime numbers and figuring out the consequences. Following a series of logical steps, it can be clearly shown that the statement cannot be true because there is a number that is the product of all primes plus 1 that is either itself prime or cannot be divided by any prime, meaning there must be a prime number greater than all the primes initially assumed. Therefore, the initial assumption must be wrong and there must instead be infinitely many prime numbers. 

I have never before seen this type of argument being used in legal decisions, probably because legal analysis is typically quite different and is rarely as clear cut as to be amenable to logical proof. The recent decision of the Enlarged Board of Appeal in G 1/23 is the first example I am aware of that actually uses this argument, which it does in coming to an apparently definitive answer to the question of whether a product that is put on the market must be reproducible by the skilled person to be considered part of the state of the art. 

The argument is used by the EB to reject an interpretation of the prior decision G 1/92 that a non-reproducible product would be entirely excluded from the state of the art. The EB first assumes that this interpretation of G 1/92 is true, i.e. that a product put on the market, if not reproducible (i.e., the skilled person cannot manufacture it from scratch using different starting materials), is entirely excluded from the state of the art. This means the product, including all its properties, is treated as if it does not exist for the purposes of assessing novelty and inventive step under Articles 54(2) and 56 EPC (see point 44).

The EB then explores the logical implications of this assumption, focusing on the concept of reproducibility and the skilled person’s reliance on common general knowledge, which is derived from the state of the art (points 50–54). The skilled person’s common general knowledge is limited to what is part of the state of the art. If non-reproducible products are excluded from the state of the art, they cannot be part of the skilled person’s common general knowledge (point 57). The EB interprets “reproduce” as manufacturing the product by a different route, not simply obtaining it from the market (point 38). Thus, the skilled person must rely on starting materials that are themselves reproducible and part of the state of the art to recreate the product (point 58). To reproduce a product, the skilled person must use starting materials that are reproducible. However, these starting materials themselves require precursor materials, which must also be reproducible, and so on (point 59). This creates a regress where every material must be reproducible without relying on merely available (but non-reproducible) materials, such as naturally occurring substances or chemical elements (point 60). The EB then argues that this assumption leads to an absurd result: if only reproducible materials can be considered part of the state of the art, then no material in the physical world would qualify as state of the art. This is because all materials ultimately rely on non-reproducible starting materials, such as chemical elements or naturally occurring substances like crude oil, which cannot be synthesized from scratch by the skilled person (points 60–63). For example, chemical elements (e.g., carbon, oxygen) cannot be reproduced; they are taken from nature or the market. Even simple compounds or raw materials (e.g., crude oil) are not trivially reproducible, yet they are undeniably part of the technical reality the skilled person works with (point 61). If non-reproducible products are excluded, the state of the art becomes an “empty set” (point 65), meaning that no technical teachings, whether from products, documents, or oral disclosures, could be considered prior art, as they all depend on non-reproducible materials at some point. This outcome is described as “manifestly absurd” (point 72) because it contradicts the practical reality that skilled persons routinely use commercially available or naturally occurring materials in their work (point 67). Since the assumption that non-reproducible products are excluded from the state of the art leads to the absurd conclusion that the state of the art is empty, the assumption must be false. Therefore, the EB concludes that a product put on the market cannot be excluded from the state of the art solely because it is not reproducible (point 80). Instead, the product and its analysable properties are part of the state of the art, regardless of reproducibility, as long as they are publicly available (Headnote I and II). As a result, the EB reinterprets G 1/92 to align with this conclusion, concluding that “reproducibility” should include obtaining the product from the market in its readily available form, rendering the enablement requirement redundant (point 73). This ensures that commercially available products, even if not reproducible by manufacturing, are part of the state of the art, and their analysable properties can be considered for novelty and inventive step assessments (point 74).

The reductio ad absurdum argument used by the EB is effective here because it shows that the enablement requirement, as suggested by an interpretation of G 1/92, leads to an impossible and impractical outcome, which would exclude all materials from the state of the art. This contradiction with technical reality and the purpose of patent law (to assess inventions against what is publicly available) forces the rejection of the enablement requirement for products that have been put on the market. The argument underscores that the state of the art should include all publicly available technical information, regardless of whether the skilled person can replicate the product from scratch. 

G 1/23 Referral - Is a marketed product prior art?

The question of whether something is made available to the public is fundamental to patent law. Article 54(1) EPC states that "An invention shall be considered to be new if it does not form part of the state of the art". Article 54(2) EPC then goes on to define what constitutes the state of the art, which is "everything made available to the public by means of a written or oral description, by use, or in any other way, before the date of filing of the European patent application". A product that is put on the market is made available to the public either by use or "in any other way", so such a product becomes part of the state of the art once on the market. A later filed patent application claiming the same product would consequently not be novel. 

There is a difference, however, between making available a product by placing the product itself on the market and making the same product available to the public by way of a disclosure, for example by publication of a paper or a patent application. In the latter case, the product itself is not disclosed but is only made available to the public if a skilled person would be able to reproduce the product based on what is disclosed. In other words, the disclosure needs to be enabling. This requirement does not (or at least should not) apply to a disclosure by placing the product on the market simply because the product itself is made available. Consequently, disclosure of the product by placing it on the market does not necessarily disclose to the skilled person how to make the product, while disclosure by publication is in effect the reverse, in that the disclosure must disclose to the skilled person how to make the product. 

Given the above, is there any question to be answered regarding whether a product is considered to be made available to the public if the skilled person might not be able to reproduce the product itself? One might think not, but this is in fact a live question that has been put before the EPO Enlarged Board of Appeal. Technical Board of Appeal decision T 438/19 has raised the following questions:

1. Is a product put on the market before the date of filing of a European patent application to be excluded from the state of the art within the meaning of Article 54(2) EPC for the sole reason that its composition or internal structure could not be analysed and reproduced without undue burden by the skilled person before that date? 

2. If the answer to question 1 is no, is technical information about said product which was made available to the public before the filing date (e.g. by publication of technical brochure, non-patent or patent literature) state of the art within the meaning of Article 54(2) EPC, irrespective of whether the composition or internal structure of the product could be analysed and reproduced without undue burden by the skilled person before that date? 

3. If the answer to question 1 is yes or the answer to question 2 is no, which criteria are to be applied in order to determine whether or not the composition or internal structure of the product could be analysed and reproduced without undue burden within the meaning of opinion G 1/92? In particular, is it required that the composition and internal structure of the product be fully analysable and identically reproducible?

Only question 1 is really of any significance. If this is answered in the negative, the other two questions are essentially pointless and don't add anything. Since it should be obvious by now that I think the answer to the first question should be a clear 'no', I will not even say anything about the other two. 

A first important point to note, which is key to answering question 1, is that it relates to a product and not to a method for making a product. In the patent in question, the product is a “material suitable as an encapsulating material for [a] solar cell” (claim 1 of the patent). The claims of the patent relate only to: i) the material itself; ii) a solar cell comprising the material; and iii) use of the material as an encapsulating material for a solar cell. There is no question regarding a method of making the material or whether such a method was made available to the public at any point. 

A second important point to note is that the alleged differentiating feature in claim 1 of the patent is only the final feature of claim 1, which is “a content of aluminum element of from 10 to 500 ppm”, the purported closest prior art disclosing all other features. Therefore, if the purported closest prior art is considered not to be excluded from the state of the art within the meaning of Article 54(2) EPC, the only question to be addressed is whether increasing the aluminum content to a value within the stated range would be obvious to the skilled person, and not whether a process of making the product in this way would be available to the skilled person. 

Thirdly, although the question of validity of the patent is one of inventive step, the question before the Enlarged Board is one only of novelty, i.e. whether the product was made available to the public before the priority date of the patent. The finding of the Enlarged Board will therefore have an effect on any case relating to whether putting a product on the market makes the product part of the state of the art for novelty or inventive step.

As a general principle, as outlined above, if a product has been put on the market and therefore made available to the public, any claim to the product itself in a later filed patent application would lack novelty. A distinction should be made between a claim to a product and a claim to a method of making the product. The former claim would be invalid over the making available to the public of the product, regardless of how the product was produced or whether the skilled person could have reproduced the product. The latter claim would only be invalid if the method of making the product was known by, or would be obvious to, the skilled person. A new method of making an existing product is patentable. The product itself produced by any other method cannot be patented a second time. 

The referral in this case stems from the following paragraph from the Enlarged Board’s reasoning in G 1/92: 

"An essential purpose of any technical teaching is to enable the person skilled in the art to manufacture or use a given product by applying such teaching. Where such teaching results from a product put on the market, the person skilled in the art will have to rely on his general technical knowledge to gather all information enabling him to prepare the said product. Where it is possible for the skilled person to discover the composition or the internal structure of the product and to reproduce it without undue burden, then both the product and its composition or internal structure become state of the art” (point 1.4 of the reasons). 

The referring board in T 438/19 indicates that the last sentence of the above passage “could appear to indicate that a product put on the market becomes state of the art and therefore available to the public only when the composition or internal structure of the product can be discovered and reproduced without undue burden” (point 8.2 of the reasons). This would, however, in my view be a misreading of both the sentence itself and the context in which it is used, which is in relation to whether a product can be reproduced. The sentence is only referring to the situation where, if the skilled person can reproduce the product without undue burden, both the product and its composition or internal structure become state of the art. The product itself is state of the art regardless of whether its composition or internal structure could be analysed, not least because the product in the same form would be an infringement of a claim to the product if placed on the market afterwards. The reference in G 1/92 to the skilled person being able to “reproduce it without undue burden” is therefore clearly referring to the skilled person being able to deduce how to “prepare the said product”, not to whether making the product available to the public before the priority date would be prior art for a claim to the product itself. This is regardless of whether the skilled person could reproduce the product with or without undue burden. The answer to question 1 must therefore be no. 

For a claim to a product, it does not matter whether the skilled person could or did reproduce the composition or internal structure of the product if the same product would be considered infringing if put on the market afterwards. A good example of this is the case of Merrell Dow Pharmaceuticals Inc. v H.N. Norton & Co. Ltd. [1996] RPC 76, a judgment from the UK House of Lords. The key finding of this was that a product (in this case an acid metabolite of an anti-histamine drug terfenadine) was made available to the public before the priority date of a patent to the product because it was an inevitable consequence of taking the drug terfenadine. Although the composition of the acid metabolite product was not made available to the public until after the filing date of the patent in question, following further research by the patentee, this did not matter. This was because, as Lord Hoffmann put it, “one cannot swallow terfenadine without shortly afterwards making the acid metabolite in one’s liver” (paragraph 7). Lord Hoffmann then quoted the Enlarged Board decision in G 2/88 (Mobil), which stated: “It is generally accepted as a principle underlying the EPC that a patent which claims a physical entity per se, confers absolute protection upon such physical entity; that is, wherever it exists and whatever its context (and therefore for all uses of such physical entity, whether known or unknown)” (point 5 of the reasons). Lord Hoffmann then went on to state that the consequence of this is that: “If the use would have been an infringement afterwards, it must have been an anticipation before”. (paragraph 25). If the Enlarged Board in G 1/23 were to find that such a principle was no longer applicable, this would allow patent claims to products already put on the market, thereby turning something that would previously not be an infringing product into an infringement. It ought to be clear that this would be a nonsense, and should not even require considering provisions such as Section 64 to allow what was done before to be continue to be done. I hope that the Enlarged Board see this and decide accordingly.

UPDATE 13 March 2025: According to an article from patent attorneys at GJE, following oral proceedings held yesterday the Enlarged Board has decided that the above 3 questions should be answered as follows: 

1. A product put on the market before the filing date of a European patent application is not excluded from the state of the art solely because its composition or internal structure could not be analyzed and reproduced without undue burden. 

2. Technical information about such commercial products (e.g., in brochures or data sheets) does constitute state of the art regardless of whether the product itself could be analyzed and reproduced. 

3. When determining what constitutes state of the art, a physical product is by definition enabled by being put on the market and analysability and reproducibility are not required.

Although we will have to see what the official decision says, it appears from this that I was completely correct and my earlier fears have been allayed. Putting a product on the market is indeed a public disclosure, making any later filed claim to the product itself invalid. 

Novelty over Generic Disclosures

For a claimed invention to be novel, it must have at least one feature that is not disclosed in a single piece of prior art, typically a document. As described in the Guidelines for Examination, G-VI 2:

"A document takes away the novelty of any claimed subject-matter derivable directly and unambiguously from that document including any features implicit to a person skilled in the art in what is expressly mentioned in the document, e.g. a disclosure of the use of rubber in circumstances where clearly its elastic properties are used even if this is not explicitly stated takes away the novelty of the use of an elastic material. The limitation to subject-matter "derivable directly and unambiguously" from the document is important. Thus, when considering novelty, it is not correct to interpret the teaching of a document as embracing well-known equivalents which are not disclosed in the documents; this is a matter of obviousness".

Novelty is therefore not quite as straightforward as simply looking through the document and deciding whether all features in the claim can be found. But what are implicit features? The above section of the Guidelines makes clear that this does not extend to well-known equivalents, which would instead fall under inventive step. There is, however, a grey area between an explicit disclosure of something and what would constitute an equivalent. 

A question I have been asking myself recently is whether implicit features would include something as simple as left and right handedness if a disclosure does not specify either but from which the skilled person would inevitably select one or the other, perhaps with equal probability but perhaps not (not a mixture, anticipating clever comments from chemists about enantiomers). If, to take as simple an example as I can think of, a document discloses a widget with a screw but does not disclose whether the screw is a left-handed or right-handed screw (and the handedness doesn't make any difference), does this anticipate a later claim to the exact same widget with a right-handed screw? 

Another section of the Guidelines, which I find has remained unchanged for at least the past 20 years, is G-VI, 5, which states: 

"In considering novelty, it is to be borne in mind that a generic disclosure does not usually take away the novelty of any specific example falling within the terms of that disclosure, but that a specific disclosure does take away the novelty of a generic claim embracing that disclosure, e.g. a disclosure of copper takes away the novelty of metal as a generic concept, but not the novelty of any metal other than copper, and one of rivets takes away the novelty of fastening means as a generic concept, but not the novelty of any fastening other than rivets".

This section of the Guidelines goes back at least as far as the 2001 edition (see the EPO archive versions), where the same wording was used in section C-IV, 7.4, and most probably much earlier than this. A puzzle I am having with this, however, is that this does not refer to any case law. I am also unsure what it means by using the word "usually". Looking in the EPO's case law book, section 5.2.6 on generic disclosure states:

"It is established case law that a specific disclosure destroys the novelty of a generic feature in a claim but that a generic disclosure does not destroy the novelty of a specific feature (see T 651/91, T 776/07, T 1174/05, T 6/04, T 776/07). A generic disclosure does not normally deprive a claimed specific embodiment of novelty (T 1786/09).

In T 651/91 the board pointed out that a generic disclosure did not normally deprive any specific example falling within that disclosure of novelty. A disclosure could be generic even where it only left open the choice between two alternatives".

The key decision therefore appears to be the earliest one mentioned here, T 651/91, which was decided in 1993. The case law book appears to make it clear that a disclosure could be generic with only two alternatives, meaning that my example above of an undefined handedness screw would not anticipate a screw with a specified handedness. Or would it? The Board only states that a disclosure could be generic if there were two alternatives, and the Guidelines states that a generic disclosure does not usually take away the novelty of a specific example. What does this decision actually say though, and what is the legal reasoning behind it? The relevant part of the decision is in points 4.3 and 4.4, which (in machine translation from the original German) state:

"4.3. Consistent with the Guidelines for Examination at C-IV, 7.4, the disclosure of a general teaching does not pre-empt the novelty of a particular practice falling under that general teaching. A teaching can be general even if it leaves open the choice between only two alternatives.

4.4. In the present case, however, more than two alternatives are included. Contrary to the opinion of the appellant, according to which the word sequence "one of the ... gears" in claim 1 of publication (D1) represents a reference to only two gear designs, one of which corresponds to Figure 1 there and the other to the gear type according to the contested patent corresponds, no such restriction can be found in the overall documentation of publication D1. As US Pat. No. 4,280,583 (D3) shows, the general teaching according to claim 1 of document D1 also includes at least the further embodiment shown there, in which three gear wheels are seated on the countershaft, one of which controls the drive member ( 8, 12) of the differential gear drives" (emphasis added).

Note that, as mentioned above, the section of the Guidelines referred to has been unchanged since at least 2001, and most likely also since the date of this decision (it would be useful to have confirmation of this). The result is that we appear to have legal reasoning from the leading case on the subject, which is referred to approvingly in 18 later cases, but which has only a reference to the Guidelines in support of its position. From everything I have been led to believe about how these things work, that seems to me to be the wrong way round. Usually the Guidelines will follow the existing case law, not the case law following the Guidelines. 

Furthermore, this leading case explicitly states that the facts of the case do not even relate to there being two alternatives, so the Board cannot have considered the possibility of left and right handedness or other equivalent situations. As far as I can work out (and I have traced the line of reasoning from all cases that refer to T 651/91), there is no case that considers the situation of exactly and only two alternatives, either of which the skilled person would inevitably select. All have followed T 651/91, finding that generic disclosures do not anticipate a specific claim. 

What if the case law is (at least partly) wrong on this point? It would of course need a fact situation to establish this, but one way of supporting an argument that a generic disclosure of a screw would anticipate both left and right handed screws can be found from case law on the subject of implicit features. An example case is T 823/96, which states at point 4.5:

"[T]he Board observes that the term "implicit disclosure" should not be construed to mean matter that does not belong to the content of the technical information provided by a document but may be rendered obvious on the basis of that content. In the Board's judgment, the term "implicit disclosure" relates solely to matter which is not explicitly mentioned, but is a clear and unambiguous consequence of what is explicitly mentioned. Therefore, whilst common general knowledge must be taken into account in deciding what is clearly and unambiguously implied by the explicit disclosure of a document, the question of what may be rendered obvious by that disclosure in the light of common general knowledge is not relevant to the assessment of what is implied by the disclosure of that document" (emphasis added).

Following this, what would be the "clear and unambiguous consequence" of following a disclosure of a widget with a screw? The skilled person would have to select a screw to make the widget, and the screw would inevitably have a handedness. Does it matter which handedness of screw the skilled person selects? Given that right handed screws are far more common, would it only apply to these? What if both were equally possible? At the moment I do not have any answers to these questions, but would be interested to see if there are flaws in the argument that a generic disclosure such as this would actually anticipate both possibilities, notwithstanding the established case law on the subject. 

By the way, I do actually have a fact situation that matches the above and would very much like to see it tested on appeal, but it is not my decision.