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Opinion for the court filed by Circuit Judge LOURIE, in which Chief Judge MICHEL and Circuit Judges NEWMAN, MAYER, BRYSON, GAJARSA, DYK, PROST, and MOORE join. Additional views filed by Circuit Judge NEWMAN. Concurring opinion filed by Circuit Judge GAJARSA. Dissenting-in-part, concurring-in-part opinion filed by Circuit Judge RADER, in which Circuit Judge LINN joins. Dissenting-in-part, concurring-in-part opinion filed by Circuit Judge LINN, in which Circuit Judge RADER joins.

Ariad Pharmaceuticals, Inc., Massachusetts Institute of Technology, the Whitehead Institute for Biomedical Research, and the President and Fellows of Harvard College (collectively, “Ariad”) brought suit against Eli Lilly & Company (“Lilly”) in the United States District Court for the District of Massachusetts, alleging infringement of U.S. Patent 6,410,516 (“the '516 patent”). After trial, at which a jury found infringement, but found none of the asserted claims invalid, a panel of this court reversed the district court’s denial of Lilly’s motion for judgment as a matter of law (“JMOL”) and held the asserted claims invalid for lack of written description. Ariad Pharms., Inc. v. Eli Lilly & Co., 560 F.3d 1366 (Fed.Cir.2009).

Ariad petitioned for rehearing en banc, challenging this court’s interpretation of 35 U.S.C. § 112, first paragraph, as containing a separate written description requirement. Because of the importance of the issue, we granted Ariad’s petition and directed the parties to address whether § 112, first paragraph, contains a written description requirement separate from the enablement requirement and, if so, the scope and purpose of that requirement. We now reaffirm that § 112, first paragraph, contains a written description requirement separate from enablement, and we again reverse the district court’s denial of JMOL and hold the asserted claims of the '516 patent invalid for failure to meet the statutory written description requirement.

BACKGROUND

The '516 patent relates to the regulation of gene expression by the transcription factor NF-éB. The inventors of the '516 patent were the first to identify NF-éB and to uncover the mechanism by which NF-éB activates gene expression underlying the body’s immune responses to infection. The inventors discovered that NFéB normally exists in cells as an inactive complex with a protein inhibitor, named “IéB” (“Inhibitor of kappa B”), and is activated by extracellular stimuli, such as bacterial-produced lipopolysaccha rides, through a series of biochemical reactions that release it from IéB. Once free of its inhibitor, NF-éB travels into the cell nucleus where it binds to and activates the transcription of genes containing a NF-éB recognition site. The activated genes (e.g., certain cytokines), in turn help the body to counteract the extracellular assault. The production of cytokines can, however, be harmful in excess. Thus the inventors recognized that artificially interfering with NF-éB activity could reduce the harmful symptoms of certain diseases, and they filed a patent application on April 21, 1989, disclosing their discoveries and claiming methods for regulating cellular responses to external stimuli by reducing NF-éB activity in a cell.

Ariad brought suit against Lilly on June 25, 2002, the day the '516 patent issued. Ariad alleged infringement of claims 80, 95, 144, and 145 by Lilly’s Evista® and Xigris® pharmaceutical products. The asserted claims, rewritten to include the claims from which they depend, are as follows:

80. [A method for modifying effects of external influences on a eukaryotic cell, which external influences induce NF-éBmediated intracellular signaling, the method comprising altering NF-éB activity in the cells such that NF-éB-mediated effects of external influences are modified, wherein NF-éB activity in the cell is reduced] wherein reducing NF-éB activity comprises reducing binding of NF-éB to NF-éB recognition sites on genes which are transcriptionally regulated by NF-éB.

*134195. [A method for reducing, in eukaryotic cells, the level of expression of genes which are activated by extracellular influences which induce NF-eBmediated intracellular signaling, the method comprising reducing NF-éB activity in the cells such that expression of said genes is reduced], carried out on human cells.

144. [A method for reducing bacterial lipopolysaccharide-induced expression of cytokines in mammalian cells, which method comprises reducing NF-éB activity in the cells so as to reduce bacterial lipopolysaccharide-induced expression of said cytokines in the cells] wherein reducing NF-éB activity comprises reducing binding of NF-éB to NF-éB recognition sites on genes which are transcriptionally regulated by NF-éB.

145. [A method for reducing bacterial lipopolysaccharide-induced expression of cytokines in mammalian cells, which method comprises reducing NF-éB activity in the cells so as to reduce bacterial lipopolysaccharide-induced expression of said cytokines in the cells], carried out on human cells.

The claims are thus genus claims, encompassing the use of all substances that achieve the desired result of reducing the binding of NF-éB to NF-éB recognition sites. Furthermore, the claims, although amended during prosecution, use language that corresponds to language present in the priority application. Specifically, the asserted claims recite methods of reducing NF-éB activity, and more specifically reducing binding of NF-éB to NF-éB recognition sites, in cells in response to external influences like bacterial lipopolysaccha rides. The specification filed on April 21, 1989, similarly recites the desired goal of reducing NF-éB activity and binding to NF-éB recognition sites in cells in response to such external influences. See '516 patent col.3 1.59-col.4 1.19; eol.311.65col.32 1.11; see also id. at col.2 11.54-59. The specification also hypothesizes three types of molecules with the potential to reduce NF-éB activity in cells: decoy, dominantly interfering, and specific inhibitor molecules. Id. at col.37 1.43-col.38 1.22.

In April 2006, the district court held a fourteen-day jury trial on the issues of infringement and validity. The jury rendered a special verdict finding infringement of claims 80 and 95 with respect to Evista® and claims 144 and 145 with respect to Xigris®. The jury also found that the asserted claims were not invalid for anticipation, lack of enablement, or lack of written description. The court denied without opinion Lilly’s motions for JMOL and, in the alternative, a new trial. In August 2006, the court conducted a four-day bench trial on Lilly’s additional defenses of unpatentable subject matter, inequitable conduct, and prosecution laches, ruling in favor of Ariad on all three issues. Ariad Pharms., Inc. v. Eli Lilly & Co., 529 F.Supp.2d 106 (D.Mass.2007).

Lilly timely appealed to this court, and on April 3, 2009, a panel affirmed in part and reversed in part. Ariad, 560 F.3d at 1369. The panel upheld the district court’s finding of no inequitable conduct, id. at 1380, but reversed the jury’s verdict on written description, holding the asserted claims invalid for lack of an adequate written description as required by 35 U.S.C. § 112, first paragraph, id. at 1376. Ariad petitioned for rehearing en banc, challenging the existence of a written description requirement in § 112, first paragraph, separate from the enablement requirement. Although not a new question, see In re Barker, 559 F.2d 588, 591-93 (CCPA 1977), its prominence has increased in recent years, see Lizardtech, Inc. v. Earth Res. Mapping, Inc., 433 F.3d 1373 (Fed.Cir.2005) (denying rehearing en banc on the question whether a separate written description requirement exists in § 112, first paragraph); Univ. of Rochester v. *1342G.D. Searle & Co., Inc., 375 F.3d 1303 (Fed.Cir.2004) (same); Enzo Biochem, Inc. v. Gen-Probe Inc., 323 F.3d 956, 970 (Fed.Cir.2002) (same). In light of the controversy concerning the distinctness and proper role of the written description requirement, we granted Ariad’s petition, vacating the prior panel opinion and directing the parties to brief two questions:

(1) Whether 35 U.S.C. § 112, paragraph 1, contains a written description requirement separate from an enablement requirement?

(2) If a separate written description requirement is set forth in the statute, what is the scope and purpose of that requirement?

In addition to the parties’ briefs, the court received twenty-five amicus briefs. Of those, seventeen were filed in support of Lilly, one was filed in support of Ariad, and seven were filed in support of neither party. The majority, including a brief filed by the United States, were filed in support of this court’s current written description doctrine. The court heard oral arguments on December 7, 2009.

DISCUSSION

I.

Although the parties differ in their answers to the court’s questions, their positions converge more than they first appear. Ariad, in answering the court’s first question, argues that § 112, first paragraph, does not contain a written description requirement separate from enablement. Yet, in response to this court’s second question on the scope and purpose of a written description requirement, Ariad argues that the statute contains two description requirements: “Properly interpreted, the statute requires the specification to describe (i) what the invention is, and (ii) how to make and use it.” Appellee Br. 1; see also id. at 43 (“[T]he written description requirement of § 112, ¶ 1 requires, first, that the specification describe (identify) what the invention is and, second, that the specification teach how to make and use the invention.”). Ariad reconciles this apparent contradiction by arguing that the legal sufficiency of its two-prong description requirement is judged by whether it enables one of skill in the art to make and use the claimed invention. Thus, according to Ariad, in order to enable the invention, the specification must first identify “what the invention is, for otherwise it fails to inform a person of skill in the art what to make and use.” Id. at 30. Yet Ariad argues that this first step of “identifying” the invention applies only in the context of priority (ie., claims amended during prosecution; priority under 35 U.S.C. §§ 119, 120; and interferences) because original claims “constitute their own description.” Id. at 44.

Lilly, in contrast, answers the court’s first question in the affirmative, arguing that two hundred years of precedent support the existence of a statutory written description requirement separate from enablement. Thus, Lilly argues that the statute requires, first, a written description of the invention and, second, a written description of how to make and use the invention so as to enable one of skill in the art to make and use it. Finally, Lilly asserts that this separate written description requirement applies to all claims— both original and amended — to ensure that inventors have actually invented the subject matter claimed.

Thus, although the parties take diametrically opposed positions on the existence of a written description requirement separate from enablement, both agree that the specification must contain a written description of the invention to establish what the invention is. The dispute, therefore, centers on the standard to be applied and whether it applies to original claim language.

*1343A.

As in any case involving statutory interpretation, we begin with the language of the statute itself. Consumer Prod. Safety Comm’n v. GTE Sylvania, Inc., 447 U.S. 102, 108, 100 S.Ct. 2051, 64 L.Ed.2d 766 (1980). Section 112, first paragraph, reads as follows:

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.

According to Ariad, a plain reading of the statute reveals two components: a written description (i) of the invention, and (ii) of the manner and process of making and using it. Yet those two components, goes Ariad’s argument, must be judged by the final prepositional phrase; both written descriptions must be “in such full, clear, concise, and exact terms as to enable any person skilled in the art ... to make and use the same.” Specifically, Ariad parses the statute as follows:

The specification shall contain

[A] a written description

[i] of the invention, and

[ii] of the manner and process of making and using it,

[B] in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same ...

Ariad argues that its interpretation best follows the rule of English grammar that prepositional phrases (here, “of the invention,” “of the manner and process of making and using it,” and “in such full, clear, concise, and exact terms”) modify another word in the sentence (here, “written description”), and that it does not inexplicably ignore the comma after “making and using it” or sever the “description of the invention” from the requirement that it be in “full, clear, concise, and exact terms,” leaving the description without a legal standard.

Ariad also argues that earlier versions of the Patent Act support its interpretation. Specifically, Ariad contends that the first Patent Act, adopted in 1790, and its immediate successor, adopted in 1793, required a written description of the invention that accomplished two purposes: (i) to distinguish the invention from the prior art, and (ii) to enable a person skilled in the art to make and use the invention.1 Ariad then asserts that when Congress assigned the function of defining the invention to the claims in 1836, Congress amended the written description requirement so that it served a single purpose: enablement.2

*1344Lilly disagrees, arguing that § 112, first paragraph, contains three separate requirements. Specifically, Lilly parses the statute as follows:

(1) “The specification shall contain a written description of the invention, and ”

(2) “The specification shall contain a written description ... of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and ”

(3) “The specification ... shall set forth the best mode contemplated by the inventor of carrying out the invention.”

Lilly argues that Ariad’s construction ignores a long line of judicial precedent interpreting the statute’s predecessors to contain a separate written description requirement, an interpretation Congress adopted by reenacting the current language of § 112, first paragraph, without significant amendment.

We agree with Lilly and read the statute to give effect to its language that the specification “shall contain a written description of the invention” and hold that § 112, first paragraph, contains two separate description requirements: a “written description [i] of the invention, and [ii] of the manner and process of making and using [the invention”]. 35 U.S.C. § 112, ¶ 1 (emphasis added). On this point, we do not read Ariad’s position to be in disagreement as Ariad concedes the existence of a written description requirement. See Appellee Br. 2 (“Under a plain reading of the statute, a patent specification ... must contain a description (i) of the invention, and (ii) of the manner and process of making and using it.”). Instead Ariad contends that the written description requirement exists, not for its own sake as an independent statutory requirement, but only to identify the invention that must comply with the enablement requirement.

But, unlike Ariad, we see nothing in the statute’s language or grammar that unambiguously dictates that the adequacy of the “written description of the invention” must be determined solely by whether that description identifies the invention so as to enable one of skill in the art to make and use it. The prepositional phrase “in such full, clear, concise, and exact terms as to enable any person skilled in the art ... to make and use the same” modifies only “the written description ... of the manner and process of making and using [the invention],” as Lilly argues, without violating the rules of grammar. That the adequacy of the description of the manner and process of making and using the invention is judged by whether that description enables one skilled in the art to make and use the same follows from the parallelism of the language.

While Ariad agrees there is a requirement to describe the invention, a few amici appear to suggest that the only description requirement is a requirement to describe enablement. If Congress had intended enablement to be the sole description requirement of § 112, first paragraph, the statute would have been written differently. Specifically, Congress could have written the statute to read, “The specification shall contain a written description of the invention, in such full, clear, concise, and exact terms as to enable any person skilled in the art ... to make and use the same,” or “The specification shall contain a written description of the manner and process of making and using the invention, in such full, clear, concise, and exact terms as to enable any person skilled in the art ... to make and use the same.” Under the amicis’ construction a portion of the stat*1345ute — either “and of the manner and process of making and using it” or “[a written description] of the invention” — becomes surplusage, violating the rule of statutory construction that Congress does not use unnecessary words. See United States v. Menasche, 348 U.S. 528, 538-39, 75 S.Ct. 513, 99 L.Ed. 615 (1955) (“It is our duty ‘to give effect, if possible, to every clause and word of a statute.’ ”) (quoting Montclair v. Ramsdell, 107 U.S. 147, 152, 2 S.Ct. 391, 27 L.Ed. 431 (1883)).

Furthermore, since 1793, the Patent Act has expressly stated that an applicant must provide a written description of the invention, and after the 1836 Act added the requirement for claims, the Supreme Court applied this description requirement separate from enablement. See infra Section I.B. Congress recodified this language in the 1952 Act, and nothing in the legislative history indicates that Congress intended to rid the Act of this requirement. On the contrary, “Congress is presumed to be aware of a[ ] ... judicial interpretation of a statute and to adopt that interpretation when it reenacts a statute without change.” Forest Grove Sch. Dist. v. T.A., — U.S. -, 129 S.Ct. 2484, 2492, 174 L.Ed.2d 168 (2009) (quoting Lorillard v. Pons, 434 U.S. 575, 580, 98 S.Ct. 866, 55 L.Ed.2d 40 (1978)).

Finally, a separate requirement to describe one’s invention is basic to patent law. Every patent must describe an invention. It is part of the quid pro quo of a patent; one describes an invention, and, if the law’s other requirements are met, one obtains a patent. The specification must then, of course, describe how to make and use the invention (i.e., enable it), but that is a different task. A description of the claimed invention allows the United States Patent and Trademark Office (“PTO”) to examine applications effectively; courts to understand the invention, determine compliance with the statute, and to construe the claims; and the public to understand and improve upon the invention and to avoid the claimed boundaries of the patentee’s exclusive rights.

B.

Ariad argues that Supreme Court precedent comports with its reading of the statute and provides no support for a written description requirement separate from enablement. Specifically, Ariad asserts that in Evans v. Eaton, 20 U.S. (7 Wheat.) 356, 433-34, 5 L.Ed. 472 (1822), the Supreme Court recognized just two requirements under § 3 of the 1793 Act, the requirements “to enable” the invention and “to distinguish” it from all things previously known. And, goes Ariad’s argument, since the 1836 Act, which removed the latter language and added the requirement for claims, the Court has consistently held that a patent applicant need fulfill but a single “written description” requirement, the measure of which is enablement.

Lilly disagrees and reads Evans as acknowledging a written description requirement separate from enablement. Lilly further contends that the Court has continually confirmed the existence of a separate written description requirement, including in O’Reilly v. Morse, 56 U.S. (15 How.) 62, 14 L.Ed. 601 (1853) under the 1836 Act; Schriber-Schroth Co. v. Cleveland Trust Co., 305 U.S. 47, 59 S.Ct. 8, 83 L.Ed. 34 (1938), under the 1870 Act; and more recently in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 736, 122 S.Ct. 1831, 152 L.Ed.2d 944 (2002).

Like Lilly, we also read Supreme Court precedent as recognizing a written description requirement separate from an enablement requirement even after the introduction of claims. Specifically, in Schriber-Schroth, the Court held that a patent directed to pistons for a gas engine with *1346“extremely rigid” webs did not adequately describe amended claims that recited flexible webs under the then-in-force version of § 112, first paragraph.3 305 U.S. at 56-57, 59 S.Ct. 8. The Court ascribed two purposes to this portion of the statute, only the first of which involved enablement:

[1] to require the patentee to describe his invention so that others may construct and use it after the expiration of the patent and [2] to inform the public during the life of the patent of the limits of the monopoly asserted, so that it may be known which features may be safely used or manufactured without a license and which may not.

Id. at 57, 59 S.Ct. 8. The Court then concluded that even if the original specification enabled the use of a flexible web, the claim could derive no benefit from it because “that was not the invention which [the patentee] described by his references to an extremely rigid web.” Id. at 58-59, 59 S.Ct. 8 (emphasis added); see also MacKay Radio & Tel. Co. v. Radio Corp. of Am., 306 U.S. 86, 98-102, 59 S.Ct. 427, 83 L.Ed. 506 (1939) (holding invalid claims amended to include structures “not within the invention described in the application” even though the variations were small). Although the Court did not expressly state that it was applying a description of the invention requirement separate from enablement, that is exactly what the Court did.4

Further, both before and after Schriber-Schroth, the Court has stated that the statute serves a purpose other than enablement. In Gill v. Wells, 89 U.S. (22 Wall.) 1, 22 L.Ed. 699 (1874), the Court held invalid a reissue patent for claiming a combination not described in the original application, but the Court also emphasized the need for all patents to meet the “three great ends” of § 26, only one of which was enablement. Specifically, the Court stated:

(1) That the government may know what they have 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.®.) That other inventors may know what part of the field of invention is unoccupied.

Id. at 25-26. Finally, most recently in Festo, the Court recited three requirements for § 112, first paragraph, and non-*1347ed a written description requirement separate from the others:

[T]he patent application must describe, enable, and set forth the best mode of carrying out the invention. These latter requirements must be satisfied before issuance of the patent, for exclusive patent rights are given in exchange for disclosing the invention to the public. What is claimed by the patent application must be the same as what is disclosed in the specification; otherwise the patent should not issue. The patent also should not issue if the other requirements of § 112 are not satisfied....

535 U.S. at 736, 122 S.Ct. 1831 (emphasis added) (internal citations omitted). As a subordinate federal court, we may not so easily dismiss such statements as dicta but are bound to follow them. See Stone Container Corp. v. United States, 229 F.3d 1345, 1349-50 (Fed.Cir.2000). While Ariad points to statements in other cases that support its view, Appellee Br. 18-19, not one disavows the existence of a separate written description requirement.

A separate written description requirement also does not conflict with the function of the claims. 35 U.S.C. § 112, ¶ 2. Claims define the subject matter that, after examination, has been found to meet the statutory requirements for a patent. See In re Vamco Mach. & Tool, Inc., 752 F.2d 1564, 1577 n. 5 (Fed.Cir.1985). Their principal function, therefore, is to provide notice of the boundaries of the right to exclude and to define limits; it is not to describe the invention, although their original language contributes to the description and in certain cases satisfies it. Claims define and circumscribe, the written description discloses and teaches.

C.

In addition to the statutory language and Supreme Court precedent supporting the existence of a written description requirement separate from enablement, stare decisis impels us to uphold it now. Ariad acknowledges that this has been the law for over forty years, see Appellee Br. 24, and to change course now would disrupt the settled expectations of the inventing community, which has relied on it in drafting and prosecuting patents, concluding licensing agreements, and rendering validity and infringement opinions. As the Supreme Court stated in admonishing this court, we “must be cautious before adopting changes that disrupt the settled expectations of the inventing community.” Festo, 535 U.S. at 739, 122 S.Ct. 1831; see also Watson v. United States, 552 U.S. 74, 82, 128 S.Ct. 579, 169 L.Ed.2d 472 (2007) (“A difference of opinion within the Court ... does not keep the door open for another try at statutory construction, where stare decisis has special force [since] the legislative power is implicated, and Congress remains free to alter what we have done.” (internal quotations omitted)). If the law of written description is to be changed, contrary to sound policy and the uniform holdings of this court, the settled expectations of the inventing and investing communities, and PTO practice, such a decision would require good reason and would rest with Congress.

D.

Ariad next argues that an incorrect reading of In re Ruschig, 54 C.C.P.A. 1551, 379 F.2d 990 (1967), by our predecessor court, the Court of Customs and Patent Appeals (“CCPA”), and then by this court, created the first written description requirement separate from enablement. Yet Ariad also asserts, in response to Lilly’s argument that In re Moore, 33 C.C.P.A. 1083, 155 F.2d 379 (1946); In re Sus, 49 C.C.P.A. 1301, 306 F.2d 494 (1962); and Jepson v. Coleman, 50 C.C.P.A. 1051, 314 F.2d 533 (1963), applied a separate written description requirement pre-Rus*1348chig, that those cases “merely tested whether the specification identified the same invention that was defined by later-added or amended claims — which is an aspect of enablement — and did not interpret § 112, ¶ 1 as containing an independent description-possession requirement.” Appellee Br. 22-23. Thus, according to Ariad, a written description of the invention is required but is not separate from enablement because it identifies the invention that must be enabled, and this, in Ariad’s view, differs from first requiring the invention to be described and then separately requiring it to be enabled.

We view this argument as a distinction without a practical difference insofar as both approaches require a written description of the invention in the specification. In either case the analysis compares the claims with the invention disclosed in the specification, and if the claimed invention does not appear in the specification, both Ariad and Lilly agree that the claim'— whether in Schriber-Schroth or Ruschig— fails regardless whether one of skill in the art could make or use the claimed invention. Ruschig involved a claim amended during prosecution to recite a specific chemical compound, chlorpropamide. 379 F.2d at 991. The specification as filed disclosed a genus encompassing about “half a million possible compounds,” but it did not disclose chlorpropamide specifically. Id. at 993. The CCPA affirmed the PTO’s rejection of the compound claim because the specification provided no guides or “blaze marks” to single out chlorpropamide from all the other compounds, and thus did not support the later-added claim. Id. at 994-95. The court also rejected the argument that one of skill in the art would be enabled to make chlorpropamide as “beside the point for the question is not whether he would be so enabled but whether the specification discloses the compound to him, specifically, as something appellants actually invented,” which, the court held, it did not. Id. at 995-96.

According to Ariad, the court properly rejected Ruschig’s claim based on enablement because the specification did not identify the later-claimed compound, leaving the skilled artisan with no guide to select that compound from the myriad of other compounds encompassed by the broad disclosure. According to Lilly, the court properly rejected the claim under a written description requirement separate from enablement because the specification did not disclose the later-claimed compound to one of skill in the art as something the inventors actually invented out of the myriad of other compounds encompassed by the broad disclosure. Again, this difference amounts to little more than semantics as the parties agree that the court properly affirmed the rejection because the original application did not disclose the specific claimed invention, chlorpropamide, even if one of skill in the art could, based on the disclosure with respect to related compounds, make and use it.

Ariad also argues that the court properly rejected Ruschig’s claim as violating 35 U.S.C. § 132’s prohibition on “new matter.” But § 132 is an examiner’s instruction, and unlike § 282 of the Patent Act, which makes the failure to comply with § 112 a defense to infringement, § 132 provides no statutory penalty for a breach. Express statutory invalidity defenses carry more weight than examiner’s instructions, and prohibiting adding new matter to the claims has properly been held enforceable under § 112, first paragraph. See In re Rasmussen, 650 F.2d 1212, 1214-15 (CCPA 1981). Regardless, one can fail to meet the requirements of the statute in more than one manner, and the prohibition on new matter does not negate the need to provide a written description of one’s invention.

*1349E.

In contrast to amended claims, the parties have more divergent views on the application of a written description requirement to original claims. Ariad argues that Regents of the University of California v. Eli Lilly & Co., 119 F.3d 1559 (Fed.Cir.1997), extended the requirement beyond its proper role of policing priority as part of enablement and transformed it into a heightened and unpredictable general disclosure requirement in place of enablement. Rather, Ariad argues, the requirement to describe what the invention is does not apply to original claims because original claims, as part of the original disclosure, constitute their own written description of the invention. Thus, according to Ariad, as long as the claim language appears in ipsis verbis in the specification as filed, the applicant has satisfied the requirement to provide a written description of the invention.

Lilly responds that the written description requirement applies to all claims and requires that the specification objectively demonstrate that the applicant actually invented — was in possession of — the claimed subject matter. Lilly argues that § 112 contains no basis for applying a different standard to amended versus original claims and that applying a separate written description requirement to original claims keeps inventors from claiming beyond their inventions and thus encourages innovation in new technological areas by preserving patent protection for actual inventions.

Again we agree with Lilly. If it is correct to read § 112, first paragraph, as containing a requirement to provide a separate written description of the invention, as we hold here, Ariad provides no principled basis for restricting that requirement to establishing priority. Certainly nothing in the language of § 112 supports such a restriction; the statute does not say “The specification shall contain a written description of the invention for purposes of determining priority.” And although the issue arises primarily in cases involving priority, Congress has not so limited the statute, and neither will we.

Furthermore, while it is true that original claims are part of the original specification, In re Gardner, 480 F.2d 879, 879 (CCPA 1973), that truism fails to address the question whether original claim language necessarily discloses the subject matter that it claims. Ariad believes so, arguing that original claims identify whatever they state, e.g., a perpetual motion machine, leaving only the question whether the applicant has enabled anyone to make and use such an invention. Oral Argument 37:26-38:00. We disagree that this is always the case. Although many original claims will satisfy the written description requirement, certain claims may not. For example, a generic claim may define the boundaries of a vast genus of chemical compounds, and yet the question may still remain whether the specification, including original claim language, demonstrates tha