concurring.
I concur in the court’s judgment finding Claim 1 of the '723 patent invalid, however, I reach the judgment by a different statutory provision. I would find Claim 1 invalid because it encompasses subject matter that is unpatentable under 35 U.S.C. § 101.1
I.
A. Authority
The question of patentability under Section 101 does not arise often, and a court’s decision to raise it sua sponte is even less common. The centrality of patentable subject matter to the entire scope of the patent law suggests that there are times when such inquiries are critical. The Supreme Court established long ago that “the question whether the invention, which is the subject-matter in controversy, is patentable or not is always open to the consideration of the court, whether the point is raised by the answer or not.” Slawson v. Grand St. R.R., 107 U.S. 649, 652, 2 S.Ct. 663, 27 L.Ed. 576 (1882). See also Richards v. Chase Elevator Co., 158 U.S. 299, 301, 15 S.Ct. 831, 39 L.Ed. 991 (1895). These precedents remain good law, though the courts have relied upon them infrequently. The policy that drove them, however, remains vibrant. Less than a decade after Slawson, in the context of an interference, the Supreme Court stressed that though
[t]he parties to the present suit appear to have been willing to ignore the question as to patentability in the present case, and to have litigated merely the question of priority of invention, on the assumption that the invention was patentable. But neither the Circuit Court nor this court can overlook the question of patentability.
Hill v. Wooster, 132 U.S. 693, 698, 10 S.Ct. 228, 33 L.Ed. 502 (1890). In contemporary patent law, 37 C.F.R. § 1.641 specifically allows an administrative patent judge to raise the issue of patentability sua sponte as to claims designated to correspond to a count of an interference.
*1322Beyond administrative proceedings, courts have found the occasional need to raise Section 101 issues sua sponte — even subsequent to the 1952 revisions to the Patent Act. At least three of our sister circuits, whose rulings on patent law prior to 1982 do not bind this court but retain persuasive value, raised Section 101 issues that the parties had not addressed. The Ninth Circuit announced that “it is the duty of the court to dismiss a patent infringement suit whenever it affirmatively appears that the patent is invalid.” Barkeij v. Lockheed Aircraft Corp., 210 F.2d 1, 2 (9th Cir.1954). According to the Second Circuit, “[e]ven were section 101 not raised by appellees, it was not error for the district court to consider it since it had the power to do so. Section 101 deals with the subject matter of patents and, as such, it is always open to the consideration of the court ...” Howes v. Great Lakes Press Corp., 679 F.2d 1023, 1028 (2d. Cir.1982). And the Third Circuit explained that
[i]t has been clear from an early date, that the court could dismiss a bill because the invention described in the patent was not patentable, even when no defense of invalidity was set up in the answer.... Accordingly, when a party brings suit on a patent alleging infringement, it is accountable for the validity of the patent....
Borden Co. v. Clearfield Cheese Co., 369 F.2d 96, 99-100 (3d. Cir.1966).
The Federal Circuit has independently raised Section 101 concerns without prompting from the parties at least once before. In Titanium Metals Corp. v. Banner, 778 F.2d 775 (Fed.Cir.1985), we considered a patent that the PTO had rejected as both anticipated under Section 102 and obvious under Section 103. Id. at 776. The district court reversed, and issued an order authorizing the Commissioner of Patents and Trademarks to issue the patent. Titanium Metals Corp. v. Mossinghoff, 603 F.Supp. 87, 91 (D.D.C.1984). The government appealed. The matter therefore reached this court on issues relevant to Sections 102 and 103, not to Section 101. We explained, however, that
[t]he patent law imposes certain fundamental conditions for patentability, paramount among them being the condition that what is sought to be patented, as determined by the claims, be new. The basic provision of Title 35 applicable here is § 101 ... The title of the application here involved is “Titanium Alloy,” a composition of matter. Surprisingly, in all of the evidence, nobody discussed the key issue of whether the alloy was new, which is the essence of the anticipation issue....
Titanium Metals, 778 F.2d at 781. We concluded that “the decision and order of the district court holding that claims 1, 2, and 3 are directed to patentable subject matter and authorizing the issuance of a patent thereon were clearly erroneous and are reversed.” Id. at 783. In other words, we recognized that we could neither affirm nor reverse the district court’s holdings under Sections 102 and 103 in a principled way without addressing the underlying erroneous assumption that the invention at issue met the requirements of Section 101. See also Brassica Protection Prods. LLC v. Sunrise Farms (In re Cruciferous Sprout Litig.), 301 F.3d 1343, 1350 (Fed.Cir.2002) (characterizing as “common sense” Titanium Metals’ rationale, including the injection of Section 101 into an anticipation analysis).
Both this court and the Supreme Court have recognized that there is a significant public policy interest in removing invalid patents from the public arena. In Cardinal Chemical Co. v. Morton International, Inc., 508 U.S. 83, 100, 113 S.Ct. 1967, 124 L.Ed.2d 1 (1993), the Supreme Court reversed our practice of vacating findings of invalidity where the court found non-in*1323fringement in light of the strong public interest in resolving questions of patent validity. In Blonder-Tongue Labs., Inc. v. University of Illinois Foundation, 402 U.S. 313, 91 S.Ct. 1434, 28 L.Ed.2d 788 (1971), the Supreme Court commented at length on the wasteful consequences of relitigating the validity of a patent after it has once been held invalid. In United States v. Glaxo Group, Ltd., 410 U.S. 52, 57-58, 93 S.Ct. 861, 35 L.Ed.2d 104 (1973), the Supreme Court ruled that the government, like patent licensees, could always challenge the validity of a patent in the course of prosecuting an antitrust action “to vindicate the public interest in enjoining violations of the Sherman Act.” The Court cited numerous cases2 as “sufficient authority” to support this holding, id., which it saw as furthering a longstanding policy orientation: “It is as important to the public that competition should not be repressed by worthless patents, as that the patentee of a really valuable invention should be protected in his monopoly....” Pope Mfg. Co. v. Gormully, 144 U.S. 224, 234, 12 S.Ct. 632, 36 L.Ed. 414 (1892).
These decisions mirror our own recognition that “[p]ublic policy requires that only inventions which fully meet the statutory standards are entitled to patents.” Constant v. Advanced Micro-Devices, Inc., 848 F.2d 1560, 1564 (Fed.Cir.1988) (citations omitted), and that “[t]here is a stronger public interest in the elimination of invalid patents than in the affirmation of a patent as valid.” Nestier Corp. v. Menasha Corp.-Lewisystems Div., 739 F.2d 1576, 1581 (Fed.Cir.1984). The best way to ensure that patents issue only for inventions in full compliance with the statutory standards is to allow “the validity of a patent, which was originally obtained in ex parte proceedings in the PTO, [to] be challenged in court.” Constant, 848 F.2d at 1564.
My belief that this case warrants a sua sponte Section 101 inquiry therefore falls well within a long if somewhat sparse tradition, driven in part by concerns of public policy but grounded entirely in legal authority. Where, as here, the facts are both unusual3 and undisputed, where the legal implication of these facts is clear, and where a consideration of fundamental aspects of law and policy is necessary to maintain the integrity of the patent law, a sua sponte inquiry into the patentability of the claimed subject matter is appropriate.
B. Claim Construction and Prior Use
Before discussing my reasons for finding Claim 1 of the '723 Patent invalid for *1324claiming unpatentable subject matter, however, I do need to address a few preliminary matters. I agree with the majority that the “single crystal” theory4 provides the only construction that is entirely consistent with the Claim l’s language claiming “crystalline paroxetine hydrochloride hemihydrate” (“paroxetine hemihyd-rate”). I also agree with the majority that the paroxetine hemihydrate “made” in Apotex’s seeded manufacturing facilities through the natural conversion of the off-patent paroxetine anhydrate and water vapor present a prima facie case of infringement.
I agree with the district court, however, that SKB is entitled to summary judgment that the '723 patent is not invalidated by prior public use, SmithKline Beecham v. Apotex Corp., 286 F.Supp.2d 925, 938 (N.D.Ill.2001) (“SK I”), because “the control [SKB] actually exercised over the trials was sufficient to demonstrate that the trials were in the nature of experimentation rather than mere commercial use,” id. at 934, and because SKB’s experiments designed to assess the product’s efficacy as an antidepressant, id. at 932, were relevant to the '723 patent in the same way that the experimental use doctrine preserved the validity of the patents in our previous cases. See Manville Sales Corp. v. Paramount Sys. Inc., 917 F.2d 544, 550 (Fed.Cir.1990); Seal-Flex, Inc. v. Athletic Track & Court Constr., 98 F.3d 1318 (Fed.Cir.1996); EZ Dock, Inc. v. Schafer Sys. Inc., 276 F.3d 1347 (Fed.Cir.2002).
In EZ Dock, for example, the patent at issue claimed a polyethylene floating dock — like the claim at issue here, a product claim. Id. at 1348. The district court determined that the patentee had offered the claimed dock for sale in the United States, more than one year before filing the patent application. Id. at 1350. We noted that though the defendant had presented a prima facie case against EZ Dock, EZ Dock’s evidence could convince a jury that the sales were experimental. Id. at 1352. We explained that though the “experiments” did not test features actually claimed in the patent, an experimental use defense was still, available because “[the inventor] testified that he sold the dock ... to determine whether it was capable of performing its intended purpose in its intended environment.” Id. at 1353.
We noted that this application of the experimental use doctrine, like our earlier assessment of experimental use in Manville, 917 F.2d at 550, extended the notion of experimentation beyond features claimed explicitly in the patent to include the intended purpose of those features. EZ Dock, 276 F.3d at 1353. The majority notes this extension with approval, and attempts to distinguish the present matter from our precedent by focusing on reduction to practice. According to the majority, SKB’s testing of paroxetine hemihydrate’s performance as a human antidepressant was not necessary to reduce paroxetine hemihydrate to practice. The majority does not make clear, however, why testing a light pole’s performance at illumination under severe weather conditions was necessary to reduce the *1325light pole to practice, Manville, 917 F.2d at 547-48, why testing an all-weather activity mat’s performance in harsh weather was necessary to reduce the mat to practice, Seal-Flex, 98 F.3d at 1320-21, or why testing a floating dock’s performance in rough, choppy water was necessary to reduce the dock to practice, EZ-Dock, 276 F.3d at 1353-54. In all four cases, the claims at issue were product claims that did not claim the tested features explicitly. In all four cases, the patentees possessed the claimed product in substantial enough form to test their products’ performance at their intended functions. The majority does not explain why only one of these four patentees had reduced its claimed invention to practice sufficiently to preclude the experimental use doctrine. I see no principled grounds on which to distinguish this case from our precedent. See Manville, 917 F.2d at 550; Seal-Flex, 98 F.3d at 1324; EZ Dock, 276 F.3d at 1353. The district court was correct in finding that, under our precedent, the prior-use bar did not invalidate the '723 Patent. SK I, 286 F.Supp.2d at 938. The majority seems to be trying to reach an ultimate conclusion of invalidity while avoiding the road less traveled.
Nevertheless, because the district court misconstrued the claim, I cannot share its conclusion that Claim 1 is “valid against the various attacks on it made by Apotex.” SmithKline Beecham Corp. v. Apotex Corp., 247 F.Supp.2d 1011, 1052 (N.D.Ill.2003) (“SK II”). Claim 1 of the '723 patent is invalid because it is broad enough to claim subject matter that is unpatentable under Section 101. The troubling implications of this impermissible breadth explain the various anomalies that engaged the district court. Under normal circumstances, patented products do not simply “appear” in ways that convert noninfring-ing products into infringing products.
The district court found as a matter of fact that paroxetine hemihydrate is an exception to this general rule. SK II, 247 F.Supp.2d at 1022-23. I agree with the majority that the record supports the district court’s factual findings, and that these findings provide the appropriate background for our legal conclusions — specifically including the district court’s findings concerning seeding and conversion.
II.
A. Theory of Infringement
Because the proper construction of Claim 1 follows the “single crystal” theory, SKB must prove that Apotex’s product does and will continue to contain at least some hemihydrate. Though SKB’s legal burden is only to prove infringement by a preponderance of the evidence, S. Bravo Systems, Inc. v. Containment Technologies. Corp., 96 F.3d 1372, 1376 (Fed.Cir.1996), SKB nevertheless faces a significant challenge. As the district court found, Apotex wants to manufacture pure anhyd-rate; any hemihydrate present in its product is an undesirable impurity. See SK II, 247 F.Supp.2d at 1015, 1025, 1045. Both SKB and the district court explicitly rejected the possibility that the anhydrous and hemihydrous forms of paroxetine came into existence simultaneously, and that every batch of paroxetine ever manufactured (or that ever will be manufactured) contains at least trace elements of hemihyd-rate — an argument that would not only prove SKB’s point about Apotex’s product, but would also invalidate the '723 Patent as inherent in the prior art. Id. at 1025.
SKB’s basic theory of infringement, which the district court recognized as establishing a prima facie case of infringement when applied to the single crystal construction, id. at 1043, rests upon two scientific principles that remain matters of controversy within the scientific communi*1326ty, both as general phenomena and as applied to paroxetine: seeding and conversion. See id. at 1021-23. Under this infringement theory, the form of paroxetine discovered in the 1970s was, indeed, pure anhydrate; hemihydrate did not exist until late 1984.
[SKB’s expert] Dr. Bernstein testified that he was ‘absolutely convinced’ that no hemihydrate had existed before December 1984 ... Dr. Terence Threlfall, Apotex’s expert on polymorphism, testified [that] Dr. Bernstein’s absolute certainty ... is not tenable. No one knows when the hemihydrate form of paroxe-tine came into existence, although it is a reasonable inference that it did not exist in a detectable amount until then.
Id. at 1022. From that date forward, however, it was impossible to produce pure anhydrate in a “seeded” environment because even under normal climactic conditions, at least some of the anhydrate would “convert” to become hemihydrate.
This process of ‘seeding’ the old with the new can be deliberate — that is, can be a method of manufacturing the new poly-morph — or adventitious, a result of the fact that some of the crystals become airborne and ‘contaminate’ the laboratory or plant in which the old crystal is being manufactured.... [T]he seeds relevant to this case are seeds that cause one polymorph to convert to another and these seeds are crystals of the form to which conversion occurs. A single tiny crystal, constituting a single seed, might induce conversion.... The creation of the new polymorph is likely to make the laboratory or plant where it is produced seeded, with the result that efforts to produce the old polymorph may instead produce the new one, since it is the more stable form. In principle it should be possible to re-create the old polymorph, just by replicating the exact procedure by which it used to be created, only this time in a seed-free environment.... [I]n practice efforts to re-create old poly-morphs do not always succeed, probably because the critical mass of molecules that is required to cause conversion is so minute....
Id. at 1020. SKB therefore argues that any paroxetine manufactured in a seeded environment must inevitably contain at least some hemihydrate, that this condition has only prevailed since some time in late 1984, and that Apotex’s facilities have been or inevitably will become seeded.
According to SmithKline, the BCI plant [in which Apotex manufactures anhyd-rate] is seeded with hemihydrate crystals because it was there that Apotex, exercising the broadened experimental-use privilege conferred by the Hatch-Waxman Act, used and made hemihyd-rate in the course of developing its anhydrous product.
Id. at 1024.
B. Findings of Fact
SKB’s proof supporting this theory must rest upon factual demonstrations. As an appellate court, we accept all facts found by the district court unless they are clearly erroneous. Shockley v. Arcan, Inc., 248 F.3d 1349, 1357 (Fed.Cir.2001). The district court, however, stated its most significant finding as an hypothesis:
The conflicting testimony of Bernstein ... on the one hand and of Threlfall on the other can largely be reconciled on the following hypothesis: while the presence of hemihydrate seeds in a batch of anhydrate is likely, provided the ambient humidity and temperature are no lower than is normal in the temperate zone, to produce conversion within a short time, once the amount converted reaches a few percent of the mixture further conversion is unlikely without substantially greater humidity, temperature, or pressure.
*1327SK II, 247 F.Supp.2d at 1022-23. Findings of fact stated as hypotheses pose particularly challenging problems for appellate courts. Did the district court accept this hypothesis as a fact upon which legal arguments and conclusions can rest, or was the district court merely trying to make sense of the scientific testimony that the two experts proffered?
The district court’s own legal conclusions make it clear that the court accepted them as facts, by stating, for example, that “[Apotex’s] BCI plant is seeded as a result of the mid-1990s experiments,” id. at 1032 (emphasis added), and that “the anhydrate as it proceeds through the process [at the BCI plant] will at several junctures be exposed to air that contains enough water molecules to permit conversion of anhyd-rate to hemihydrate.” Id. These statements make sense only if the district court found that both seeding and conversion are valid scientific facts, at least as applied to paroxetine for the purposes of this case.
The district court’s understandable hedging of its language when dealing with controversial scientific theories nevertheless led it to definitive factual conclusions: “BCI probably will be ‘making’ at least some hemihydrate crystals and therefore infringing, at least prima facie, patent 723 if claim 1 is interpreted to cover single crystals of the hemihydrate.” Id. (emphasis added). “Some conversion from anhyd-rate to hemihydrate is likely to occur in a seeded facility in which the anhydrate is exposed to air; BCI’s plant is seeded; and the anhydrate manufactured there is exposed to nondehumidified air before it leaves the plant.” Id. (emphasis added). But in concrete syllogistic conclusion, “[t]his evidence is sufficient to support an inference that BCI will be making at least tiny amounts of the hemihydrate if it is permitted to manufacture the anhydrate.” Id. (emphasis added).
The district court therefore found, as a matter , of fact, that paroxetine anhydrate in a séeded environment characterized by normal'climactic conditions can convert itself spontaneously into paroxetine hemih-ydrate. Id. The district court further found that SKB had met its burden of proving, by a preponderance of the evidence, that such conversion was inevitable at Apotex’s BCI manufacturing facility. Id. at 1042-43.
The district court next turned to consider Apotex’s defenses. “If ... claim 1 is valid and will be infringed ... by a single crystal of hemihydrate ... [then]. Apotex has a complete affirmative defense that SmithKline is the cause of the infringement.” Id. at 1052. This conclusion makes sense only after a factual finding that Apo-tex’s legal- experimentation with Paxil5 seeded the BCI plant. Id. at 1024. “Apo-tex cannot eliminate all crystals of hemih-ydrate; under a single-crystal interpretation of claim 1, [and] SmithKline is the sole cause of infringement.” Id. at 1044 (emphasis in the original).
Finally, the district court explained that it is difficult, and in some cases it may be impossible (paroxetine hydrochloride hemihydrate may be one of those cases — no one knows), to destroy all the seeds in seeded premises.... Dr. Bernstein testified that if Apotex, desperate to avoid a charge of infringement built a new plant in Antarctica where no hemih-ydrate seeds had ever been and started manufacturing anhydrate there, and a *1328depressed worker in the plant dropped a Paxil on the floor, the result might be to seed the plant and make it impossible from then on to produce pure anhydrate there.
Id. at 1020-21.
In short, the district court made four critical factual findings: (1) Hemihydrate crystals did not exist before their first emergence in an SKB laboratory in late 1984, id. at 1025; (2) Hemihydrate seeds spread easily, and increasingly large parts of the environment are becoming seeded, id. at 1020-21; (3) Under normal climactic conditions in a seeded environment, at least some anhydrate crystals will convert spontaneously to become hemihydrate crystals,' id. at 1022-23 and (4) Apotex’s manufacturing facilities have been seeded, id. at 1024.
III.
A. Public Notice
These findings of fact highlight the unique challenge that the infringement analysis of the '723 Patent poses: infringing matter has an unusual tendency to “appear” even where it is unwanted. Such a spontaneous appearance of a patented product vitiates the public notice function of patents. See id. at 1028. Under normal circumstances,
one of ordinary skill in the art should be able to read a patent, to discern which matter is disclosed and discussed in the written description, and to recognize which matter has been claimed. The ability to ■ discern both what has been disclosed and what has been claimed is the essence of public notice. It tells the public which products or processes would infringe the patent and which would not.
PSC Computer Prods. v. Foxconn Int'l, 355 F.3d 1353, 1359 (Fed.Cir.2004). When the claimed product can be “made” via the spontaneous conversion of a noninfringing product into an infringing one, adequate notice is impossible — even if the claimed product was initially synthesized in a laboratory.
Long before 1952, when Section 112 formalized the modern written description requirement, the Supreme Court observed that:
Whoever discovers that a certain useful result will be produced, in any art, machine, manufacture, or composition of matter, by the use of certain means, is entitled to a patent for it; provided he specifies the means he uses in a manner so full and exact, that any one skilled in the science to which it appertains, can, by using the means he specifies, without any addition to, or subtraction from them, produce precisely the result he describes. And if this cannot be done by the means he describes, the patent is void. And if it can be done, then the patent confers on him the exclusive right to use the means he specifies to produce the result or effect he describes, and nothing more.
O’Reilly v. Morse, 15 How. 62, 119, 14 L.Ed. 601 (1853). The Supreme Court further explained that
[a]ccurate description of the invention is required by law, for several important purposes: 1. That the government may know what is granted, and what will become public property when the term of the monopoly expires. 2. That licensed persons desiring to practice the invention may know during the term how to make, construct, and use the invention. 3. That other inventors may know what part of the field of invention is unoccupied.
Bates v. Coe, 98 U.S. 31, 39, 25 L.Ed. 68 (1878). While these pre-1952 cases may not apply directly to the modern written description requirement of Section 112, they do demonstrate the longstanding cen*1329trality of the public notice function to patent policy.
Paroxetine hemihydrate forces us, for the first time, to confront the requirement that “a patentee specify in a manner so full and exact, that any one skilled in the science to which it appertains, can, by [avoiding] the means he specifies,” O’Reilly, 15 How. at 119, 14 L.Ed. 601, avoid producing the claimed product. Otherwise, there will be no way for “other inventors [to] know what part of the field of invention is unoccupied.” Bates, 98 U.S. at 39. Effective notice is impossible if a natural physical process can convert a noninfringing product into an infringing one.
The district court was correct in concluding that Claim 1 of the '723 patent, subject to the proper single crystal construction, fails to provide suitable notice. SK II, 247 F.Supp.2d at 1028, 1052. A paroxetine anhydrate manufacturer, such as Apotex, could exert reasonable efforts to manufacture only products already in the public domain, could direct its entire production process toward developing only products that scrupulously respected all patent rights, and could nevertheless infringe because a natural physical process acting upon its legitimate anhydrous product “made” new hemihydrous crystals that Apotex then “sold” to the public. “Apotex has tried to prevent conversion of its product to the patented form and a principal issue in this case is whether it has succeeded; there is no suggestion that Apotex desires conversion.” SK II, 247 F.Supp.2d at 1015 (emphasis in original).
Were we to nevertheless hold Apotex liable as an infringer of Claim 1, we would effectively remove a valuable public-domain antidepressant, paroxetine anhyd-rate, from the market, and likely motivate potential inventors of superior grades of paroxetine to refocus their efforts elsewhere. This result is inconsistent with patent policy and — more importantly for the purposes of this court — it is incompatible with patent law. We would be holding valid a patent incapable of serving its important public notice function.
Claim 1 therefore cannot be held valid. But the failure of notice is a consequence of its invalidity, not the source of it. We must consider whether or not the '723 patent covers only patentable subject matter. See Slawson, 107 U.S. at 652, 2 S.Ct. 663.
B. Patentable Subject Matter
“Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefore ...” 35 U.S.C. § 101. The Supreme. Court has interpreted this statutory range of patentable subject matter to be quite broad, but hardly universal. “In choosing such expansive terms as ‘manufacture’ and ‘composition of matter,’ modified by the comprehensive ‘any,’ Congress plainly contemplated that the patent laws would be given wide scope.” Diamond v. Chakrabarty, 447 U.S. 303, 308, 100 S.Ct. 2204, 65 L.Ed.2d 144 (1980). That wide scope nevertheless excludes laws of nature, natural phenomena, and abstract ideas. “Such discoveries are ‘manifestations of ...' nature, free to all men and reserved exclusively to none.’” Id. at 309, 100 S.Ct. 2204, (quoting Funk Bros. Seed Co. v. Kalo Inoculant Co., 333 U.S. 127, 130, 68 S.Ct. 440, 92 L.Ed. 588 (1948)). See also Diamond v. Diehr, 450 U.S. 175, 185, 101 S.Ct. 1048, 67 L.Ed.2d 155 (1981); Parker v. Flook, 437 U.S. 584, 589, 98 S.Ct. 2522, 57 L.Ed.2d 451 (1978).
“Phenomena of nature, though just discovered, mental processes, and abstract intellectual concepts are not patentable, as they are the basic tools of scientific and technological work.” Gottschalk v. Benson, 409 U.S. 63, 67, 93 S.Ct. 253, 34 *1330L.Ed.2d 273 (1972). A single standard applies to product claims and process claims alike. Id. “[W]hether patents are allowable for [challenged subject matter] is not a matter of discretion, but of law.... Either the subject matter falls within Section 101 or it does not.” Animal Legal Def. Fund v. Quigg, 982 F.2d 920, 929-30 (Fed.Cir.1991). And as a matter of law, the critical distinction guiding all Section 101 inquiries into the patentability of subject matter is that human-made, or synthetic, products or processes are patentable, while products and processes of nature are not. See Chakrabarty at 313, 100 S.Ct. 2204; J.E.M. AG Supply v. Pioneer Hi-Bred Int’l, 534 U.S. 124, 130, 122 S.Ct. 593, 151 L.Ed.2d 508 (2001).
The district court found as a matter of fact that at some point, likely in late 1984, something occurred in SKB’s laboratories that gave rise to two new phenomena simultaneously. SK II, 247 F.Supp.2d at 1021-22. The first was a synthetic crystal later named paroxetine hemihydrate, id., ostensibly a patentable human-made invention under Chakrabarty. The second was a natural physical process whereby paroxetine anhydrate (a pre-existing synthetic crystal that today is in the public domain) could, under normal climactic conditions 'and with no human intervention, bond with water molecules and convert itself into paroxetine hemihydrate, SK II, 2A1 F.Supp.2d at 1021-22, ostensibly an unpatentable, newly discovered natural process under ChakrabaHy.
This distinction between the synthetic product and its natural “reproduction” process is subtle, but critical. Paroxetine hemihydrate is not the first invention to blur the line' between a natural' process and a synthetic product, nor is it the first to engender confusion in the patent law. In the Nineteenth Century, the conflation of the natural acoustical principles of telephony with the invention of telephone equipment gave rise to massive litigation. See Telephone Cases, 126 U.S. 1, 8 S.Ct. 778, 31 L.Ed. 863 (1888). In disentangling this complex patent litigation, the Supreme Court noted that:
In one of the cases on appeal ... the court says: “There can be no patent for a mere principle. The discoverer of a natural force or a scientific fact cannot have a patent for that.” But it proceeds to make this exception nugatory by confounding the natural process (or scientific fact) with the invented process for working the apparatus; sustaining the patent for the last upon a construction which blindly sweeps in the first.
Id. at 270-71, 8 S.Ct. 778. The '723 patent similarly confounds the scientific fact of paroxetine conversion with the invented product of paroxetine hemihydrate — and SKB similarly asks us to “sustain[] the patent for the last upon a construction which blindly sweeps in the first.” Id. We should not only decline to do so, as the majority has and as the district court did in the alternative, but we should be clear about both the character and the implications of the underlying request.
Paroxetine hemihydrate is presumably a synthetic compound, created by humans in a laboratory, never before existing in nature, that is nevertheless capable of “reproducing” itself through a natural process. SK II, 247 F.Supp.2d at 1022-23. This crystalline compound raises a question similar to one that might arise when considering the invention of a fertile plant or a genetically engineered organism, capable of reproduction, released into the wild. Consider, for example, what might happen if the wind blew fertile, genetically modified blue corn protected by a patent, from the field of a single farmer into neighboring cornfields. The harvest from those fields would soon contain at least some patented blue corn mixed in with the *1331traditional public domain yellow corn— thereby infringing the patent. The wind would continue to blow, and the patented crops would spread throughout the continent, thereby turning most (if not all) North American corn farmers into unintentional, yet inevitable, infringers.6 The implication — that the patent owner would be entitled to collect royalties from every farmer whose cornfields contained even a few patented blue stalks — cannot possibly be correct. The underlying question that engaged the district court, and that led it to develop numerous alternative holdings, is why this implication is incorrect.
At oral argument, when faced with this hypothetical, SKB expressed its belief that such a blue-corn patent would be “very strong.” Such a belief is misplaced. The implicit concept of “inevitable infringement” stems from the inevitable failure of the patent to provide public notice — which, in turn, stems from the inherently unpat-entable nature of the claimed subject matter.
This Section 101 problem therefore brings us full circle, back to the impossibility of public notice. Under normal circumstances, inventors other than the patentee will understand how to avoid infringing a patent by avoiding the claimed product. Because products, such as our hypothetical blue corn or SKB’s paroxetine hemihyd-rate, that can be “made” through a natural process of spontaneous conversion imply inevitable infringement, no combination of claim language and written description could possibly teach even one skilled in the art how to avoid infringement. It is unsurprising that a requirement considered so trivial for most patentable products that we are content to let it remain implicit, namely a lesson in infringement avoidance, is effectively impossible for subject matter unpatentable under Section 101. In short, patent claims drawn broadly enough to encompass products that spread, appear, and “reproduce” through natural processes cover subject matter unpatentable under Section 101 — and are therefore invalid.
C. Invalidity
Technological advances have forced this court, our predecessor court, and the Supreme Court to consider the line between the natural and the non-natural- — including such inventions as non-naturally occurring plants and bacteria — several times over the past few decades. See, e.g., In re Bergy, 596 F.2d 952 (CCPA 1979), rev’d sub nom Diamond v. Chakrabarby, 447 U.S. 303, 100 S.Ct. 2204, 65 L.Ed.2d 144 (1980); Pioneer Hi-Bred Intl, Inc. v. J.E.M. Agric. Supply, Inc., 200 F.3d 1374 (Fed.Cir.2000), affd. 534 U.S. 124, 122 S.Ct. 593, 151 L.Ed.2d 508 (2001). Parox-etine hemihydrate now appears to be the first patent litigated that forces the courts to consider the patentability of products and/or processes launched in a laboratory and released into nature.
Despite the complexity of the issue, the analysis is straightforward. An invention synthesized for the first time in a laboratory is eligible for patent protection under Section 101. Processes for producing this synthetic product in the laboratory and/or for using this synthetic product may also be eligible for patent protection under Section 101. However, a natural reproduction process, whether sexual, asexual, part of a chain reaction, or a process of decay, is ineligible for patent protection under Section 101. Chakrabarty, 447 U.S. at 309, 100 S.Ct. 2204; Funk Bros., 333 U.S. at *1332130, 68 S.Ct. 440. An item reproduced by such a natural process, whether an inorganic structure or a life form, must ipso facto be ineligible for patent protection under Section 101.
The Supreme Court has cited with approval the Congressional Record surrounding the adoption of the Plant Patent Act of 1930:
[A] plant discovery resulting from cultivation is unique, isolated, and is not repeated by nature, nor can it be reproduced by nature unaided by man. ...” S.Rep. No. 315, supra, at 6; H.R.Rep. No. 1129, supra, at 7. Congress thus recognized that the relevant distinction was not between living and inanimate things, but between products of nature, whether living or not, and human-made inventions.
Chakrabarty, 447 U.S. 303, 100 S.Ct. 2204, 65 L.Ed.2d 144 (emphasis added). In its recent ruling confirming that hybrid plants are patentable subject matter under Section 101, the Supreme Court noted that “[hjybrid plants ... generally do not reproduce true-to-type, i.e., seeds produced by a hybrid plant do not reliably yield plants with the same hybrid characteristics. Thus, a farmer who wishes to continue growing hybrid plants generally needs to buy more hybrid seed.” 534 U.S. at 128, 122 S.Ct. 593.
The principle unifying these statements about patentability made in 1930,1980, and 2001 is that products capable of being “reproduced by nature unaided by man,” Chakrabarty, 447 U.S. 303, 100 S.Ct. 2204, are not patentable subject matter under Section 101. Though the parties have not briefed this question directly, they and the district court have provided more than sufficient facts to obtain a dispositive and incontrovertible legal determination that Claim 1 of the '723 Patent is invalid under Section 101.
The '723 patent, correctly construed, claims every single crystal of paroxetine hemihydrate, including those crystals arising through natural conversion. The district court properly admitted SKB’s proffered expert testimony about the scientific mechanism underlying natural conversion, SK II, 247 F.Supp.2d at 1019-20, under Daubert v. Merrell Dow Pharmaceuticals, 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993), and General Electric v. Joiner, 522 U.S. 136, 118 S.Ct. 512, 139 L.Ed.2d 508 (1997), weighed it in conjunction with contradictory testimony proffered by Apo-tex’s experts, SK II, 247 F.Supp.2d at 1022, and concluded that at least some of Apotex’s anhydrate would convert itself to hemihydrate. SK II, 247 F.Supp.2d at 1022-23.
These findings lead to an inescapable conclusion — a conclusion that the majority attempts to dismiss as a question of “scope,” rather than of patentability. Had SKB claimed “synthetic or non-naturally occurring crystalline paroxetine hydrochloride hemihydrate,” the claim would have covered only patentable subject matter, and Apotex would be entitled to a judgment of noninfringement. Had SKB explicitly claimed the crystals converted in Apotex’s facilities, as either “the natural process of converting paroxetine an-hydrate to paroxetine hemihydrate” or “crystalline paroxetine hydrochloride hem-ihydrate arising through natural conversion,” unpatentability under Section 101 would be manifest; though the claimed matter would be a useful composition, it would be one that occurred in nature. See Chakrabarty, 447 U.S. at 309, 100 S.Ct. 2204; Funk Bros., 333 U.S. at 130, 68 S.Ct. 440. By claiming simply “crystalline paroxetine hydrochloride hemihyd-rate” with no reference to how it was produced, SKB effectively claimed “crystalline paroxetine hydrochloride hemihyd-rate whether non-naturally occurring or *1333arising through natural conversion.” Claim 1, as issued, therefore combines patentable and unpatentable subject matter, and is invalid under Section 101. The “confusion” to which the majority alludes should never arise because we cannot reach Section 102 unless the claimed matter can overcome the hurdle of Section 101.
Inventors wishing to claim products that can either be synthesized in laboratories or generated by natural processes may protect themselves by incorporating negative limitation terms like “non-natural” or “non-human” into the claims that they submit for examination. See Amgen Inc. v. Hoechst Marion Roussel, 314 F.3d 1313, 1329 (Fed.Cir.2003); Animal Legal Def. Fund, 932 F.2d at 923; In re Wakefield, 422 F.2d at 904. SKB made no such distinction. SKB, despite ah early recognition of seeding and conversion, SK II, 247 F.Supp.2d at 1022, claimed all paroxetine hemihydrate crystals, including both those “born” of natural conversion without human intervention and those “made” in a laboratory through explicit human effort. SKB further demonstrated its claim to a possessory right in naturally occurring crystals by pursuing this litigation, and articulated this claim explicitly during oral argument.
IV.
The asserted breadth of Claim 1 makes sense only under the erroneous belief that patents may protect products spread and reproduced by natural processes, directly contradicting our well established understanding of the limits imposed by Section 101. Given current scientific trends, such a belief could easily lead to misdirected research investments, to inappropriately issued patents, and to a widespread in terrorem effect crippling entire industries whose artisans learn that even their best efforts to respect patent rights may not save them from liability as inadvertent, inevitable infringers. As the district court recognized, the notice function of patents is meaningless in such an environment, SK II, 247 F.Supp.2d at 1028. The lack of suitable notice could easily chill innovation, inquiry, experimentation, and commercial development.
Though the majority’s approach to invalidating Claim 1 of the '723 patent under Section 102(b) defuses these negative consequences with respect to paroxetine, it does so at the cost of creating unfortunate precedent that will complicate future considerations of the experimental use doctrine. It also fails to address the central anomaly that the district court identified. We do no one any favors by allowing this important question to remain open. We should announce, as a court, that the patent law does not sanction the concept of inevitable infringement — lest someone mistakenly believe that it does.
I would hold that because SKB’s assertion of the single crystal theory provides the correct construction of Claim 1, the '723 patent claims paroxetine hemihydrate crystals reproduced by nature unaided by man — -unpatentable subject matter — and is therefore invalid under 35 U.S.C. § 101.
. "Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title.” 35 U.S.C. § 101.
. Telephone Cases, 167 U.S. 224, 17 S.Ct. 809, 42 L.Ed. 144 (1897); United States v. U.S. Gypsum Co., 333 U.S. 364, 68 S.Ct. 525, 92 L.Ed. 746 (1948); Sola Elec. Co. v. Jefferson Elec. Co., 317 U.S. 173, 63 S.Ct. 172, 87 L.Ed. 165 (1942); Edward Katzinger Co. v. Chicago Metallic Mfg. Co., 329 U.S. 394, 67 S.Ct. 416, 91 L.Ed. 374 (1947); and MacGregor v. Westinghouse Elec. & Mfg. Co., 329 U.S. 402, 67 S.Ct. 424, 91 L.Ed. 380 (1947); Pope Mfg. Co. v. Gormully, 144 U.S. 224, 234, 12 S.Ct. 632, 36 L.Ed. 414 (1892); Lear, Inc. v. Adkins, 395 U.S. 653, 670, 89 S.Ct. 1902, 23 L.Ed.2d 610 (1969).
. The district court's maze of alternative claim constructions and theories finding Apo-tex not liable for infringement, plus the theory added by the majority, attest to the unique circumstances of this case. The district court’s opinion, and in particular its attempt to introduce a novel equitable defense, SmithKline Beecham Corp. v. Apotex Corp., 247 F.Supp.2d 1011, 1043-45 (N.D.Ill.2003) ("SK II"), strongly imply that something “feels wrong” about holding an infringer liable for inevitable, spontaneous infringement. We therefore face a choice. We can either address the issue head-on and explain why an attempt to patent unpatentable subject matter leads to so many apparent anomalies, or we can try to contort the aspects of patent law raised by the parties in order to avoid those anomalies. I believe that the law is best served by adopting the straightforward approach.
. The district court defined the "single crystal” theory of Claim 1 as encompassing:
all manifestations of the hemihydrate, no matter how or where produced, or in what quantity relative to the mixture of which it is a part; even if the production was inadvertent, unavoidable though undesired, and wholly without benefit to the producer or detriment to SmithKline in the sense of cutting into SmithKline's market; and even if the amount is so tiny as to be beyond the limits of detection of any instrument present or foreseeable and the product in which it unexpectedly pops up does not compete with anything made or sold by SmithKline.
SK II, 247 F.Supp.2d at 1026 (emphasis in original).
. Under the Hatch-Waxman Act, ,a generic drug manufacturer is allowed to experiment with a patented drug to prove that its planned product is bioequivalent to one already approved by the Food and Drug Administration (FDA). The district .court viewed this statutory permission as .an implied license, SK II, 247 F.Supp.2d at 1018, and attributed liability for the consequent seeding to SKB. Id. at 1044.
. Although intent is not a factor in determining infringement, public notice is required as a predicate to the validity of a patent. Jurgens v. CBK, Ltd., 80 F.3d 1566, 1570 n. 2 (Fed.Cir.1996). The hypothetical causes unavoidable infringement even in situations where the public would, in good faith, want to avoid infringing.