Full opinion text
Newman, Lourie, Moore, and Wallach join, and in which Circuit Judges Dyk and Reyna concur in result. Opinion filed by Circuit Judge Moore, in which Circuit Judges Newman and O’Malley join. Opinion filed by Circuit Judge Reyna, in which Circuit Judge Dyk joins, and in which Chief Judge Prost and Circuit Judges Taranto, Chen, and Hughes join in part. Opinion .filed by Circuit Judge Taranto, in which Chief Judge Prost and Circuit Judges Chen and Hughes join, dissenting from the judgment, and in which Circuit Judges Dyk and Reyna join in part in other respects. Opinion dissenting from the judgment filed by Circuit Judge Hughes, in which Circuit Judge Chen joins. O’MALLEY, Circuit Judge. In this appeal, we consider the proper allocation of the burden of proof when amended claims are proffered during inter partes review proceedings (“IPRs”) under the Leahy-Smith America Invents Act (“AIA”), Pub. L. No. 112-29, § 6(a)-(c), 125 Stat. 284-341 (2011) (provisions creating inter partes review codified in ch. 31 of Title 35, 35 U.S.C. §§ 311-19 (2012)). Specifically, we consider how the AIA’s statutory language in 35 U.S.C. § 316(e), which places “the burden of proving a proposition of unpatentability by a preponderance of the evidence” onto the petitioner in an IPR, applies to claim amendments authorized by 35 U.S.C. § 316(d), and whether the Patent Trial and Appeal Board’s (“Board”) current practices with respect to amendments accord with that application. A panel of our court concluded that the Board did not abuse its discretion in denying Appellant Aqua Products, Inc.’s (“Aqua”) motion to amend various claims of U.S. Patent No. 8,273,183 (“the ’183 patent”) during the course of an IPR. In re Aqua Prods., Inc., 823 F.3d 1369, 1373-74 (Fed. Cir. 2016) (hereinafter “Panel Decision”). The court granted Aqua’s request for en banc rehearing and vacated the panel decision. In re Aqua Prods., Inc., 833 F.3d 1335 (Fed. Cir. 2016) (en banc) (per curiam). Upon review of the statutory scheme, we believe that § 316(e) unambiguously re-> quires the petitioner to prove all propositions of unpatentability, including for amended claims. This conclusion is dictated by the plain language of § 316(e), is supported by the entirety of the statutory scheme of which it is a part, and is reaffirmed by reference to relevant legislative history. Because a majority of the judges participating in this en banc proceeding believe the statute is ambiguous on this point, we conclude in the alternative that there is no interpretation of the statute by the Director of the Patent and Trademark Office (“PTO”) to which this court must defer under Chevron, U.S.A. Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). And we believe that, in the absence of any required deference, the most reasonable reading of the AIA is one that places the burden of persuasion with respect to the patentability of amended claims on the petitioner. Finally, we believe that the Board must consider the entirety of the record before it when assessing the patentability of amended claims under § 318(a) and must justify any conclusions of unpatentability with respect to amended claims based on that record. Because the participating judges have different views—both as to the judgment we should reach and as to the rationale we should employ in support of that judgment, as explained below, today’s judgment is narrow. The final written decision of the Board in this case is vacated insofar as it denied the patent owner’s motion to amend the patent. The matter is remanded for the Board to issue a final decision under § 318(a) assessing the patentability of the proposed substitute claims without placing the burden of persuasion on the patent owner. I. Procedural History Automated swimming pool cleaners, such as those disclosed in the ’183 patent, typically propel themselves in a swimming pool using motor-driven wheels, water jets, suction, or a combination thereof. Panel Decision, 823 F.3d at 1371. The ’183 patent discloses a jet-propelled pool cleaner with controlled directional movement and without an electric drive motor. ’183 patent, col. 10,1. 41-eol. 11,1. 3; id. col. 18, 11. 11-20. The parties began litigating questions of infringement and validity related to this patent in district court. Aqua Prods., Inc. v. Zodiac Pool Sys., Inc., No. 12-09342 (S.D.N.Y.). While that litigation was pending, Zodiac Pool Systems, Inc. petitioned the Board for inter partes review on claims 1-14, 16, and 19-21 of the T83 patent, asserting invalidity under 35 U.S.C. § 102 and § 103 in light of several prior art references. The Board instituted an IPR on claims 1-9, 13, 14, 16, and 19-21 of the ’183 patent, but not on claims 10-12. Panel Decision, 823 F.3d at 1372. Aqua then moved to substitute claims 1, 8, and 20 of the ’183 patent with proposed claims 22, 23, and 24, respectively. Id. Aqua asserted that substitute claims 22-24 complied with 35 U.S.C. § 316(d) because they did not enlarge the scope of the original claims or introduce new matter. Id. Aqua further argued that the substitute claims responded to and were patentable over the obviousness combinations at issue in the IPR. Id. The Board denied Aqua’s motion to amend. Although the Board' expressly found that Aqua’s amendments complied with the requirements of § 316(d) and 37 C.F.R. § 42.121(a)(2)(i)-(ii) (2015), the Board concluded Aqua had failed to prove the substitute claims were patentable. Aqua timely appealed that decision to this court. On appeal, Aqua argued that it did not bear the burden of proving the patentability of its proposed substitute claims. Aqua relied on the plain language of § 316(e)— which we discuss below—for its contention. The panel rejected Aqua’s argument based on this court’s precedent, which “has upheld the Board’s approach of allocating to the patentee the burden of showing that its proposed amendments would overcome the art of record.” Panel Decision, 823 F.3d at 1373 (citing Proxyconn, 789 F.3d at 1307-08; Prolitec, 807 F.3d at 1363; and Nike, 812 F.3d at 1333-34). The panel declined to “revisit the question of whether the Board may require the patentee to demonstrate the patentability of substitute claims” and held that “the burden of showing that the substitute claims were patentable rested with Aqua.” Id. The panel also rejected Aqua’s objection to the Board’s failure to consider the entirety of the record before it when assessing the patenta-bility of the amended claims. Aqua specifically objected to the Board’s refusal to consider: (1) certain' arguments Aqua made in its motion to amend; (2) arguments made in its reply to the petitioner’s challenge to its motion to amend; (3) substantial evidence in the IPR record that the cited prior art did not teach the limitations it sought to add by amendment; and (4) substantial evidence in the record of objective indicia of non-obviousness. Id. at 1373-74. Aqua sought rehearing en banc of that panel decision. We granted Aqua’s petition for en banc rehearing. In re Aqua Prods., Inc., 833 F.3d at 1336. We proposed two questions in the en banc order: (a) When the patent owner moves to amend its claims under 35 U.S.C. § 316(d), may the PTO require the patent owner to bear the burden of persuasion, or a burden of production, regarding patentability of the amended claims as a condition of allowing them? Which burdens are permitted under 35 U.S.C. § 316(e)? (b) When the petitioner does not challenge the patentability of a proposed amended claim, or the Board thinks the challenge is inadequate, may the Board sua sponte raise patentability challenges to such a claim? If so, where would the burden of persuasion, or a burden of production, lie? Id. We have jurisdiction over this appeal under 28 U.S.C. § 1295(a)(4)(A) and 35 U.S.C. § 141(c). II. The Context in Which the Questions Presented Arise With its enactment of the AIA in 2011, Congress created IPRs to provide “quick and cost effective alternatives to litigation.” H.R. Rep. No. 112-98, pt. 1, at 48 (2011). In an IPR, a third party may petition the Director to review previously-issued patent claims in an adjudicatory setting. To initiate an IPR, a petitioner must show a reasonable likelihood that it would prevail with respect to at least one of the claims challenged. See 35 U.S.C. § 314(a). Following institution by the Director and a trial before the Board, the Director may “cancel any claim that the agency finds to be unpatentable” under 35 U.S.C. § 102 and.§ 103, based on cited prior art consisting of patents or printed publications. Cuozzo Speed Techs., LLC v. Lee, — U.S. -, 136 S.Ct. 2131, 2136, 195 L.Ed.2d 423 (2016). The Board reaches its conclusions based on a preponderance of the evidence and, in doing so, employs the broadest reasonable interpretation of the challenged claims for unexpired patents. Id. at 2144-46. In Cuozzo, the Supreme Court emphasized that the patent owner’s opportunity to amend its patent in IPRs is what justifies the Board’s use of the broadest reasonable interpretation standard in IPRs: The patent holder may, at least once in the process, make a motion to do just what he would do in the examination process, namely, amend or narrow the claim. § 316(d) (2012 ed.). This opportunity to amend, together with the fact that the original application process may have presented several additional opportunities to amend the patent, means that use of the broadest reasonable construction standard is, as a general matter, not unfair to the patent holder in any obvious way. Id. at 2145. In its statement to the Senate Committee on the Judiciary several years before Congress enacted the AIA, the PTO explained that amendments are a key feature of post-grant proceedings: The [jPTO’s proposal is thus designed to put review of the propriety of patent claims that the public regards as important in the hands of senior, legally qualified officials with experience in dispute resolution. It is designed to be more efficient than litigation, while preserving enough of the full participation accorded to parties in litigation that challengers will be willing to risk being bound by the result. By providing for the possibility of amendment of challenged claims, the proposed system would preserve the merited benefits of patent claims better than the win-all or lose-all validity contests in district court. Patent Quality Improvement: Post-Grant Opposition: Hearing Before the Sub-comm. on Courts, the Internet, and Intellectual Property of the H. Comm, on the Judiciary, 108th Cong. 10 (2004) (hereinafter “PTO Gen. Counsel Toupin Statement”) (emphasis added) (statement of PTO General Counsel James A. Toupin). Indeed, the PTO has more than once acknowledged that use of the broadest reasonable interpretation standard is only appropriate when patent owners have the opportunity to amend. The PTO has explained that, “[s]ince patent owners have the opportunity to amend claims during IPR, [post-grant review and covered business method (“CBM”)] trials, unlike in district court proceedings, they are able to resolve ambiguities and overbreadth through this interpretive approach, producing clear and defensible patents at the lowest cost point in the system.” Office Patent Trial Practice Guide, 77 Fed. Reg. 48756, 48764 (Aug. 14, 2012). Simply put, the patent owner’s right to propose amended claims is an important tool that may be used to adjust the scope of patents in an IPR. See 35 U.S.C. § 316(d)(3) (entitled “Scope of claims.”); see also Cuozzo, 136 S.Ct. at 2144 (quoting Precision Instrument Mfg. Co. v. Auto. Maint. Mach. Co., 324 U.S. 806, 816, 65 S.Ct. 993, 89 L.Ed. 1381 (1945)). Congress deemed the patent owner’s right to amend so important that, in § 316(d), it mandated that the patent owner be permitted to amend the patent as of right at least once during the course of an IPR, provided certain specified statutory conditions were met. 35 U.S.C. § 316(d)(1); see also S. Rep. No. 110-259, at 22 (2008) (stating that, “[djuring the proceeding, the patent holder has one opportunity as a matter of right to amend the claims ...” (emphasis added)); 154 Cong. Rec. 22626 (2008) (statement of Sen. Kyi on S. 3600) (concluding that written institution decisions would be desirable because they give the “patent owner a sense of what issues are important to the board and where he ought to focus his amendments”). Four Congresses considered the post-grant review procedures that eventually became the AIA with little debate or controversy on the issue of amendment. Compare, e.g., S. 3818, 109th Cong. § 318 (2006), with H.R. 1249, 112th Cong. § 326 (2011). The right to amend actually was given added emphasis during this time. In the Patent Reform Act of 2006, the language authorizing amendments shifted from “entitled to request” to the present text providing for the opportunity for amendment as of right through a motion to amend. Compare H.R. 2795, 109th Cong. § 327 (2005), mth S. 3818, 109th Cong. § 318 (2006). The Senate report on S. 1145 stated that patent owners would be given “one opportunity as a matter of right to amend the claims.” See, e.g., S. Rep. No. 110-259, at 22 (2008). The House Report for the AIA, in its “Section-by-Section” explanation of the bill as finally enacted, states that the statute provides that: The patent owner may submit one amendment with a reasonable number of substitute claims, and additional amendments either as agreed to by the parties for settlement, for good cause shown in post-grant review, or as prescribed in regulations by the Director in inter partes review. H. Rep. No. 112-98, pt. 1, at 76 (2011) (emphasis added). In this report, several representatives noted with approval the high rate of “modification or nullification” of patent claims in inter partes reexamination and their desire to retain this feature in IPRs. Id. at 164. In other words, Congress saw the amendment process in IPRs as analogous to narrowing reissues, albeit prompted by a third-party challenger. Despite repeated recognition of the importance of the patent owner’s right to amend during IPR proceedings—by Congress, courts, and the PTO alike—patent owners largely, have been prevented from amending claims in the context of IPRs. A February 2017 study noted that the Board has only granted eight motions to amend in post-issuance review proceedings (six in IPRs and two in CBM proceedings). Binal J. Patel et al., Amending Claims at the PTAB—A Fool’s Errand?, Managing Intellectual Property (Feb. 24, 2017), http:// www.managingip.com/Article/3663698/ Amending-claims-at-the-PTABa-fools-errandhtml. The PTO’s statistics confirm that patent owners have consistently failed to obtain their requested relief on motions to amend. As of April 30, 2016, the Board had completely denied 112 of 118 motions to amend made by patent owners in IPRs, and partially denied motions to amend in four of the six remaining trials. USPTO, PTAB Motion to Amend Study, 2-4 (Apr. 30, 2016), https://www.uspto.gov/sites/ default/files/documents/2016-04-30% 20PTAB% 20MTA% 20study.pdf. Aqua and its amici contend that these statistics are a direct result of the Board’s placement of the burden of proving the patenta-bility of amended claims on the patent owner, its requirement that the patent owner satisfy that burden on the face of a 25-page motion to amend—without regard to the remainder of the record—and its requirement that the patent owner prove patentability, not just in response to the grounds of unpatentability asserted by the petitioner, but on all possible grounds and in light of all prior art known to the patent owner. MasterImage 3D, Inc. v. RealD Inc., No. IPR2015-00040, 2015 WL 10709290, at *2-4 (P.T.A.B. July 15, 2015) (clarifying Idle Free Sys., Inc. v. Bergstrom, Inc., No. IPR2012-00027, 2013 WL 5947697, at *4 (P.T.A.B. June 11, 2013)). We now assess whether the Board’s current practice of placing the substantive burden of proving patentability on the patent owner with regard to claim amendments proffered in IPRs may be employed in pending IPRs. We conclude it may not. III. Relevant Statutory and Regulatory Schemes The AIA provides that a patent holder in an IPR “may file 1 motion to amend the patent,” either by cancelling any challenged patent claim or by “propos[ing] a reasonable number of substitute claims.” 35 U.S.C. § 316(d)(1). Additional joint motions to amend may be permitted to “materially advance the settlement of a proceeding under section 317.” Id. § 316(d)(2). Section 316(d)(3) dictates that an amendment “may not enlarge the scope of the claims of the patent or introduce new matter.” Id. § 316(d)(3). In the same statutory section that discusses motions to amend, the following subsection appears: (e) Evidentiary Standards.—In an inter partes review instituted under this chapter, the petitioner shall have the burden of proving a proposition of unpa-tentability by a preponderance of the evidence. Id. § 316(e). This subsection immediately follows the provision describing a patent owner’s right to propose substitute claims in lieu of those challenged in an IPR. When an IPR is instituted and not dismissed subsequently, the Board “shall issue a final written decision with respect to the patentability of any patent claim challenged by the petitioner and any new claim added under section 316(d).” Id. § 318(a). The statute provides that, following the final written decision and any subsequent appeal, the Director shall incorporate “in the patent ... any new or amended claim determined to be patentable.” Id. § 318(b). The AIA delegates authority to the Director to “prescribe regulations ... establishing and governing inter partes review” and, relevant to this appeal, to “set[ ] forth standards and procedures for allowing the patent owner to move to amend the patent” under § 316(d). Id. §§ 316(a)(4), (a)(9). Invoking this authority, the Director promulgated 37 C.F.R. § 42.121, which sets forth several procedures for amending claims during an IPR. This regulation permits a patent owner to file one motion to amend after conferring with the Board but “no later than the filing of a patent owner response” unless the Board has provided an alternative due date.' 37 C.F.R. § 42.121(a)(1). Under this regulation, the Board may deny a motion to amend if the amendment does not satisfy the requirements of § 316(d)(3)—i.e., if it expands the claim scope, introduces new matter, or if it “does not respond to a ground of unpatent-ability involved in the trial.” Id. § 42.121(a)(2). The patent owner is also restricted to proposing a “reasonable number of substitute claims.” Id. § 42.121(a)(3). The Director promulgated 37 C.F.R. § 42.20 to govern all motion practice before the Board. In relevant part, Rule 42.20(a) requires that any “[rjelief, other than a petition requesting the institution of a trial, must be requested in the form of a motion.” Rule 42.20(c) states additionally that “[t]he moving party has the burden of proof to establish that it is entitled to the requested relief.” While these rules do not say so expressly, the PTO claims in this appeal that the Board has interpreted Rules 42.20 and 42.121 to place the burden of persuasion on a patent owner to demonstrate, by a preponderance of the evidence, that any proposed amended claims are patentable, that it must do so in light of prior art not already part of the IPR, and that the Director has endorsed that interpretation. Specifically, in Idle Free, a six-member panel of the Board held that the patent owner must show why the proposed amended claims are patentable over not only the prior art at issue in the IPR, but also “over prior art not of record but known to the patent owner.” 2013 WL 5947697, at *4. Then, in Masterlmage, another Board panel discussed Idle Free’s holding that “the burden is ... on the patent owner to show patentable distinction over the prior art of record 'and also prior art known to the patent owner.” 2015 WL 10709290, at *1 (quoting Idle Free, 2013 WL 5947697, at *4) (emphasis altered from original). Among other things, the panel emphasized that the ultimate burden of persuasion regarding the question of patentability is on the patent owner. Id. None of the specifics set forth in these two panel decisions regarding a patent owner’s burden are set forth in either Rule 42.20 or Rule 42.121 and none were discussed in the 2012 Federal Register comments relating to the promulgation of those Rules. And neither opinion was published in the Federal Register. IV. Our Prior Decisions As in this case, prior panels of this court have endorsed the Board’s practice of placing the burden of demonstrating the pat-entability of amendments over the prior art on the patent owner, or have been interpreted as doing so. See Proxyconn, 789 F.3d at 1307-08; Prolitec, 807 F.3d at 1363; Synopsys, 814 F.3d at 1323-24; Nike, 812 F.3d at 1333—34; Panel Decision, 823 F.3d at 1373. In Proxyconn and Prolitec, given the parties’ arguments, we did not engage in any statutory analysis—with respect to § 316(d), § 316(e), or otherwise. We also did not analyze whether the Board either did or properly could impose the burden of proving the ultimate patentability of amended claims on the patent owner. It was not until Synopsys and Nike that we had occasion to address § 316(e). In Synopsys, Mentor objected to the denial of its motion to amend, which the Board predicated on Mentor’s failure to prove patentability over prior art references not at issue in the IPR—and over all other prior art of record. Synopsys, 814 F.3d at 1323. Relying on Proxyconn, we concluded that the scope of the burden imposed by the Board was not unreasonable. Id. We then turned to Mentor’s argument that Proxyconn was distinguishable because— unlike the patent owner in Proxyconn— Mentor objected to bearing the burden of proving the patentability of its proposed amended claims, relying on § 316(e). Id. We rejected Mentor’s argument in one paragraph: Section 316(e) does not alter our analysis. ... The introductory phrase referring to an “inter partes review instituted under this chapter” makes clear that this provision specifically relates to claims for which inter partes review was initiated, ie., the original claims of the patént that a party has challenged in a petition for review. Inter partes review was not initiated for the claims put forward in the motion to amend. Id. at 1323-24. We revisited § 316(e) in Nike. There, we read § 316(e) narrowly for the reasons cited in Synopsys. Nike, 812 F.3d at 1334. We also relied on the Director’s authority under § 316(a)(9) to set “standards and procedures ... ensuring that any information submitted by the patent owner in support of any amendment entered under subsection (d) is made available to the public.” Id. at 1333 (quoting 35 U.S.C. § 316(a)(9)). On these grounds, we concluded that Nike’s “attempt to undo our conclusion in Proxyconn ... is not persuasive.” Id. at 1334. We, thus, have had limited opportunity or cause to address the first question posed and fleshed out in this en banc proceeding. We now examine these earlier holdings in light of the language of § 316(d) and § 316(e) and the governing statutory scheme of which they are a part. V. Discussion A. The Petitioner Bears the Burden to Prove All Propositions of Unpatentability Our first en banc question asks whether the PTO may require the patent owner to bear the burden of persuasion or a burden of production regarding the patentability of amended claims, given the language of 35 U.S.C. § 316(d) and § 316(e). In re Aqua Prods., 833 F.3d at 1336. The parties do not dispute that Congress delegated authority to the Director to promulgate regulations “setting forth standards and procedures for allowing the patent owner to move to amend the patent under [§ 316(d)].” 35 U.S.C. § 316(a)(9). It is upon this authority and its own reading of § 316(d) that the PTO claims it predicates its practices regarding motions to amend in IPRs and the attendant burdens it imposes in that context. We review the PTO’s regulations and statutory interpretation pursuant to Chevron and Auer v. Robbins, 519 U.S. 452, 117 S.Ct. 905, 137 L.Ed.2d 79 (1997). Chevron requires a court reviewing an agency’s construction of a statute it administers to determine first “whether Congress has directly spoken to the precise question at issue.” 467 U.S. at 842, 104 S.Ct. 2778. If the answer is yes, the inquiry ends, and we must give effect to Congress’s unambiguous intent. Id. at 842-43, 104 S.Ct. 2778. If the answer is no, the court must consider “whether the agency’s answer [to the precise question at issue] is based on a permissible construction of the statute.” Id. at 843, 104 S.Ct. 2778. The agency’s “interpretation governs in the absence of unambiguous statutory language to the contrary or unreasonable resolution of language that is ambiguous.” United States v. Eurodif S.A., 555 U.S. 305, 316, 129 S.Ct. 878, 172 L.Ed.2d 679 (2009) (citing United States v. Mead, 533 U.S. 218, 229-30, 121 S.Ct. 2164, 150 L.Ed.2d 292 (2001)). When a statute expressly grants an agency rulemaking authority and does not “unambiguously direct[]” the agency to adopt a particular rule, the agency may “enact rules that are reasonable in light of the text, nature, and purpose of the statute.” Cuozzo, 136 S.Ct. at 2142 (citing Mead, 533 U.S. at 229, 121 S.Ct. 2164, and Chevron, 467 U.S. at 843, 104 S.Ct. 2778). When the PTO does adopt rules, moreover, “[w]e accept the [Director’s] interpretation of Patent and Trademark Office regulations unless 'that interpretation is plainly erroneous or inconsistent with the regulation.” In re Sullivan, 362 F.3d 1324, 1326 (Fed. Cir. 2004) (citing Auer, 519 U.S. at 461-62, 117 S.Ct. 905, and Bowles v. Seminole Rock & Sand Co., 325 U.S. 410, 414, 65 S.Ct. 1215, 89 L.Ed. 1700 (1945) (internal quotations omitted)). 1. Chevron Step One Thus, we begin our examination of § 316(d) and § 316(e) with the language of the statute. Hughes Aircraft Co. v. Jacobson, 525 U.S. 432, 438, 119 S.Ct. 755, 142 L.Ed.2d 881 (1999) (“As in any case of statutory construction, our analysis begins with the language of the statute.” (internal quotation marks and citation omitted)). In considering that language, we must assure ourselves that we have employed all “traditional tools of statutory construction” to determine whether Congress intended to resolve the issue under consideration. Chevron, 467 U.S. at 843 n.9, 104 S.Ct. 2778. We also “must read the words ‘in their context and with a view to their place in the overall statutory scheme.’ ” King v. Burwell, — U.S. -, 135 S.Ct. 2480, 2489, 192 L.Ed.2d 483 (2015) (quoting FDA v. Brown & Williamson Tobacco Corp., 529 U.S. 120, 133, 120 S.Ct. 1291, 146 L.Ed.2d 121 (2000)). We believe Congress explicitly placed the burden of persuasion to prove propositions of unpatentability on the petitioner for all claims, including amended claims. This interpretation is compelled by the literal text of § 316(e), the overall statutory scheme for IPRs set forth in the AIA, and its legislative history. We believe, moreover, that this interpretation is consistent with the language and purpose of § 316(d). a. Section 316(d) Does Not Impose Any Burden of Proof Regarding the Patent-ability of Proposed Amended Claims The PTO claims that § 316(d)(1) unambiguously places the burden on the patent owner to prove the patentability of any proposed amended claim. Its statutory argument is twofold. First, the PTO argues that the fact that § 316(d)(1) states the patent owner may “propose” substitute claims unequivocally allows the Board to deny any motion at its discretion. Specifically, the PTO believes that Congress’s use of the words “may” and “propose” indicates not that a patent owner is given a discretionary choice about whether to amend in the circumstances described, but rather that the Board has the unfettered discretion to refuse an amendment. This, the PTO believes is true even where the amendment falls within the statutorily-authorized categories of amendments and where the amendment satisfies the requirements of § 316(d)(3)—i.e., is non-broadening and does not introduce new subject matter. The PTO’s reading of § 316(d)(1) is contravened by the plain language of the statute: § 316(d)(1) says “the patent owner may” move to amend, not that the Board may or may not allow such a motion regardless of its content. It is also inconsistent with the purpose of § 316(d) which, as noted above, was to provide a patent owner with the ability to amend a challenged claim at least once as a matter of right, so long as the proposed amended claim conforms to the statutory requirements and any reasonable procedural rules. Indeed, the PTO’s reasoning would render the amendment process virtually meaningless, rather than make the possibility of amendment the central feature of the IPR process it was intended to be. We are charged with construing statutes, “not isolated provisions.” King, 135 S.Ct. at 2489 (quoting Graham County Soil & Water Conservation Dist. v. United States ex rel. Wilson, 559 U.S. 280, 290, 130 S.Ct. 1396, 176 L.Ed.2d 225 (2010)); United States v. Morton, 467 U.S. 822, 828, 104 S.Ct. 2769, 81 L.Ed.2d 680 (1984) (“We do not, however, construe statutory phrases in isolation; we read statutes as a whole.”). Second, the PTO contends that, because § 316(d)(1) says the patent owner may seek to amend by “motion,” the amendment process unequivocally puts the burden of persuasion regarding the patenta-bility of the amendment on the patent owner because movants bear the burden of proof on motions. For these reasons, the PTO contends that § 316(e) is not even relevant to the amendment process. Specifically, the PTO asserts: “Contrary to Aqua Products’ argument, the statute providing for motions to amend in inter partes review proceedings places the burden of showing patentability on the patent owner when it states, ‘the patent owner may file one motion to amend the patent,’ as the movant bears the burden on a motion.” PTO Intervenor Br. 19 (quoting 35 U.S.C. § 316(d)) (emphasis in original). It claims that, because § 316(d) says proposed amendments may be introduced by motion, the substantive burden of persuasion on the patentability of that amendment must he imposed on the movant. We reject that contention. The PTO’s argument begs the question: what is the relief sought by the “motion” authorized in § 316(d)(1)? As noted, the patent owner may proffer amendments that propose to cancel any challenged claim and propose a reasonable number of substitute claims as long as the substitute claims (1) do not impermissibly enlarge the scope of the claims, and (2) do not introduce new subject matter. 35 U.S.C. § 316(d)(1), (d)(3). These requirements describe a threshold showing the Board must deem satisfied before the amended claims can be considered in—i.e., “entered into”— an IPR. This showing by the patent owner is not the same as the burden of proof on the question of patentability. The “request” made by a motion to amend is—in the PTO’s own words—for “entry” into the IPR, not for entry of an amended claim into the patent. Once entered into the proceeding, the amended claims are to be assessed for patentability alongside the original instituted claims. The PTO acknowledged this structure in its explanation of final Rule 42.121: [T]he first motion to amend need not be authorized by the Board. The motion will be entered so long as it complies with the timing and procedural requirements. Additional motions to amend will require prior Board authorization. All motions to amend, even if entered, will not result automatically in entry of the proposed amendment into the patent. Changes to Implement Inter Partes Review Proceedings, Post-Grant Review Proceedings, and Transitional Program for Covered Business Method Patents, 77 Fed. Reg. 48,680, 48,690 (Aug. 14, 2012) (hereinafter “Changes to Implement IPRs”) (emphases added). Thus, any propositions of substantive unpatentability for amended claims are assessed following entry of the amended claims into the IPR proceeding, under the standards that apply to all claims in the proceeding. The PTO justifies the burden it seeks to impose on the mov-ant under § 316(d)(1) by mischaraeterizing the nature of the relief sought by a motion made under that provision. Once the motions at issue are properly characterized, the PTO’s statutory argument falls apart. To conclude otherwise would conflate two concepts that are traditionally treated as distinct: the use of motions to raise evidentiary issues in adversarial proceedings versus the overall allocation of evidentiary burdens to the respective parties when rendering decisions on such motions. For example, although the movant has the burden to file a well-supported summary judgment motion before a court will consider it, if the underlying burden of persuasion rests with the other party, that underlying burden never shifts. See Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 255-56, 106 S.Ct. 2505, 91 L.Ed.2d 202 (1986); Celotex Corp. v. Catrett, 477 U.S. 317, 322-23, 106 S.Ct. 2548, 91 L.Ed.2d 265 (1986). We have noted that the “shifting burdens ... in district court litigation parallel the shifting burdens ... in inter partes reviews.” Dynamic Drinkware, LLC v. Nat’l Graphics, Inc., 800 F.3d 1375, 1378-81 (Fed. Cir. 2015). In district court, the party asserting invalidity of a patent claim bears the burden of establishing invalidity. 35 U.S.C. § 282(a). That burden of proof never shifts to the patent owner. Pfizer, Inc. v. Apotex, Inc., 480 F.3d 1348, 1359-60 (Fed. Cir. 2007). Cuozzo explains that the burden of proof in an IPR is one of the “adjudicatory characteristics” of an IPR that “make these agency proceeding's similar to court proceedings.” 136 S.Ct. at 2143. Congress expressly considered the degree of proof in IPRs. and made clear in § 316(e) that it is to be by a preponderance of the evidence—unlike that required in district court proceedings. Congress knew how to create distinctions between trial proceedings and IPRs when it so chose; Congress chose not to do so when allocating the burden of proving un-patentability. For these reasons, we believe that the only reasonable reading of the burden imposed on the movant in § 316(d) is that the patent owner must satisfy the Board that the statutory criteria in § 316(d)(1)(a)—(b) and § 316(d)(3) are met and that any reasonable procedural obligations imposed by the Director are satisfied before the amendment is entered into the IPR. Only once the proposed amended claims are entered into the IPR does the question of burdens of proof or persuasion on propositions of unpatentability come into play. It is at that point, accordingly, that § 316(e) governs, placing that burden onto the petitioner. b. The Unambiguous Language of § 316(e) We have explained that, “[i]n an inter partes review, the burden of persuasion is on the petitioner to prove ‘unpatentability by a preponderance of the evidence,’ 35 U.S.C. § 316(e), and that burden never shifts to the patentee.” In re Magnum Oil Tools Int’l, Ltd., 829 F.3d 1364, 1375 (Fed. Cir. 2016) (quotation marks and citation omitted). The parties do not dispute that § 316(e) places the burden of persuasion for already issued, challenged claims on the petitioner. Based on the plain and unambiguous language of this provision, we believe that § 316(e) applies equally to proposed substitute claims. An instituted proposition of unpatenta-bility is considered throughout the IPR. It is only finally determined when the Board issues a final written decision. Both by statute and by the PTO’s own directives, any proposed amendment must seek to cancel a challenged claim and/or propose a substitute for a challenged claim, and it must do so by responding tp an instituted ground of unpatentability. See 35 U.S.C. § 316(d)(1); see also 37 C.F.R. § 42.121(a)(2)(i). The structure of an IPR does not allow the patent owner to inject a wholly new proposition of unpatentability into the IPR by proposing an amended claim. The patent owner proposes an amendment that it believes is sufficiently narrower than the challenged claim to overcome the grounds of unpatentability upon which the IPR was instituted. When the petitioner disputes whether a proposed amended claim is patentable, it simply continues to advance a “proposition of unpa-tentability” in an “inter partes review instituted under this chapter.” 35 U.S.C. § 316(e). Contrary to other provisions of Chapter 31, which repeatedly make distinctions between original and amended claims, the “proposition of unpatentability” referenced in § 316(e) is not tethered to only one type of claim. For example, §§ 316(a)(9) and 316(d) distinguish a “challenged claim” from “substitute claims.” Similarly, § 314(a) only applies to “claims challenged in the petition.” In § 318(a), Congress distinguished between “any patent claim challenged by the petitioner” and “any new claim added under section 316(d).” And in § 318(b), Congress explained the procedure for issuing a certificate confirming the patentability of claims “and incorporating in the patent ... any new or amended claim determined to be patentable.” In § 318(c), Congress provided for intervening rights with respect to “proposed amended or new elaim[s] determined to be patentable” and incorporated into the patent following an IPR. In contrast, § 316(e) does not reference “claims” at all, nor does it use the broader term “patent” to limit its scope. And, contrary to the dissent’s reading of it, there is no language in § 316(e) that confines its application to original claims for which an IPR has been instituted under § 314(a). Section 316(e) reaches every proposition of unpatentability at issue in the proceeding. Congress could have distinguished between proposed amended claims and originally challenged claims in § 316(e), but it did not. Congress is presumed to have acted intentionally when it made the dis-tinetion between challenged and amended claims in multiple parts of the AIA statutory scheme, yet declined to do the same in § 316(e). See Bates v. United States, 522 U.S. 23, 29-30, 118 S.Ct. 285, 139 L.Ed.2d 215 (1997) (“[W]here Congress includes particular language in one section of a statute but omits it in another section of the same Act, it is generally presumed that Congress acts intentionally and purposely in the disparate inclusion or exclusion.” (quoting Russello v. United States, 464 U.S. 16, 23, 104 S.Ct. 296, 78 L.Ed.2d 17 (1983))). Section 316(e) uses the term “unpatenta-bility,” which may refer to either pending or issued claims, rather than the term “invalidity,” which both courts and the PTO apply only to issued claims. See, e.g., 35 U.S.C. § 282(a) (explaining that a “presumption of validity” attaches to issued patent claims and assigning “[t]he burden of establishing invalidity of a patent or any claim thereof’ to the challenger); In re Cyclobenzaprine Hydrochloride Extended-Release Capsule Patent Litig., 676 F.3d 1063, 1080 n.7 (Fed. Cir. 2012) (“[I]n the litigation context, validity, rather than pat-entability, is the issue.”); MPEP § 706 (9th ed. Rev. 7, Nov. 2015) (explaining that “issues pertinent to patentability” arise in “the course of examination and prosecution,” while “validity” is applicable after the claims issue). Congress’s use of “unpa-tentability,” rather than “invalidity,” in § 316(e) to assign the burden of proof to the petitioner in IPRs is significant—Congress’s choice reflects its intention that the burden of proof be placed on the petitioner for all propositions of unpatentability arising during IPRs, whether related to originally challenged or entered amended claims. The Director is instructed by § 318(a) to issue a final decision on the patentability of both “any patent claim challenged by the petitioner and any new claim added under section 316(d).” Id. § 318(a) (emphasis added). And § 318(b) uses “patentable” in connection with both issued claims and amended claims. See id. § 318(b). If the Board decides that an original.or entered amended claim overcomes the petitioner’s unpatentability challenge, the claim is “patentable” and treated as a valid claim, regardless of how the claim arose. See id. § 318(a) (referring to determining “the patentability of any patent claim challenged by the petitioner and any new claim added under section 316(d)” (emphasis added)); accord id. § 318(b). Whether a claim is “patentable” or “unpatentable” depends on the content of the claim, not who carried the burden of persuasion. See id. § 318(b) (characterizing an original claim as “unpatentable” when a cancellation certificate issues or “patentable” when a confirmation certificate issues, even though the petitioner has the burden of persuasion in both instances). The terms “patentability” and “unpa-tentability” do not raise separate inquiries; if they did, Congress would not have placed the burden of proving “unpatenta-bility” on the petitioner in § 316(e) and then required the Board to issue a decision on “patentability” in § 318(a) as if that were a disparate concept. Read together— which is how related statutory sections should be read—§ 316(e) and § 318(a)-(b) explain that, if the petitioner does not prove a claim (whether original or amended) to be “unpatentable,” the Board should find the claim to be “patentable.” See, e.g., Coit Indep. Joint Venture v. Fed. Sav. & Loan Ins. Corp., 489 U.S. 561, 573, 109 S.Ct. 1361, 103 L.Ed.2d 602 (1989); see also Brown & Williamson, 529 U.S. at 133, 120 S.Ct. 1291. The introductory clauses of § 316(e) (“In an inter partes review instituted under this chapter”), § 316(d)(1) (“During an inter partes review instituted under this chapter”), and § 318(a) (“If an inter partes review is instituted and not dismissed under this chapter ,.. ”) lend further support to our reading of § 316(e). All of these clauses use essentially the same introductory language. If the introductory clause in § 316(e) were limited to only original claims—as we concluded in Synopsys and Nike—the introductory clauses of § 316(d)(1) and § 318(a) also would have to be so limited. See Sorenson v. Sec’y of the Treasury, 475 U.S. 851, 860, 106 S.Ct. 1600, 89 L.Ed.2d 855 (1986) (“The normal rule of statutory construction assumes that ‘identical words used in different parts of the same act are intended to have the same meaning.’ ” (quoting Helvering v. Stockholms Enskilda Bank, 293 U.S. 84, 87, 55 S.Ct. 50, 79 L.Ed. 211 (1934) (quoting Atl. Cleaners & Dyers, Inc. v. United States, 286 U.S. 427, 433, 52 S.Ct. 607, 76 L.Ed. 1204 (1932))).) This conclusion would make little sense, however; as discussed above, the plain language of § 316(d)(1) and § 318(a) refers to both original and amended claims. “[I]nterpretations of a statute which would produce absurd results are to be avoided if alternative interpretations consistent with the legislative purpose are available.” Griffin v. Oceanic Contractors, Inc., 458 U.S. 564, 575, 102 S.Ct. 3245, 73 L.Ed.2d 973 (1982). A patent owner may only file a motion to amend as part of an already-instituted IPR. Because proposed amended claims are “entered into” and become part of the “inter partes review instituted under this chapter” so long as the patentee shows that they are non-broadening, supported by the specification, and responsive to a ground already at issue in the IPR, it would be illogical to construe these introductory clauses in an inconsistent fashion. The location of § 316(e) within § 316 itself further indicates that this provision applies to all claims in an IPR—whether existing or proposed to be amended. Section 316(e) is one of the five subsections in § 316, entitled “Conduct of inter partes review.” Section 316(e) immediately follows the subsection discussing the requirements for amended claims in IPRs. The lack of any reference to a burden of persuasion in the amendment subsection of § 316(d), while including an express reference to it one subsection later, indicates that Congress intended § 316(e) to apply to all claims considered in an IPR, including those authorized in the immediately preceding subsection. See 35 U.S.C. § 316. None of the other provisions in § 316 limit the application of § 316(e) in IPRs, nor are any of these subsections meant to be read in isolation—they describe the conduct of the proceeding as a whole. Indeed, Congress did not speak to burdens of proof or persuasion in IPRs anywhere else in the AIA; § 316(e) stands as its only command on that issue. For all these reasons, the dissent’s contention that “Congress wás writing a rule only for the class of claims that it recognized as necessarily having been challenged as unpatentable by a ‘petitioner’ ” in § 316(e) is untenable. Taranto Op. at 1348. To accept that proposition, one would have to divorce consideration of proposed amended or substitute claims from the issued and challenged claims which they, by right, seek to modify or replace. But, both by virtue of the text of § 316(d) and the' plain language of Rule 42.121, that cannot be done; the very unpatentability challenges by the petitioner are the same un-patentability challenges to which any proposed amendment must respond and which continue throughout the proceeding. These are not different “classes” of claims. c. Reading § 316(e) in the Context of the AIA As noted before, an Act of Congress “should not be read as a series of unrelated and isolated provisions.” Gustafson v. Alloyd Co., Inc., 513 U.S. 561, 570, 115 S.Ct. 1061, 131 L.Ed.2d 1 (1995); see also King, 135 S.Ct. at 2489. Because the presence of ambiguity in the meaning of a term “may only become evident when placed in context” within the statute, we next examine how § 316(e) fits within the overall statutory framework of the AIA. King, 135 S.Ct. at 2489 (citation omitted). The Supreme Court has instructed us to look to “[t]he text of the ... provision [at issue], along with its place in the overall statutory scheme, its role alongside the Administrative Procedure Act [ (“APA”) ], the prior interpretation of similar patent statutes, and Congress’s purpose in crafting inter partes review” to interpret each provision of the AIA. Cuozzo, 136 S.Ct. at 2141. The ultimate meanings of § 316(d) and § 316(e) must be “compatible with the rest of the law.” Util. Air Regulatory Grp. v. ERA, — U.S. -, 134 S.Ct. 2427, 2442, 189 L.Ed.2d 372 (2014). Read in context of the overall statutory scheme, we believe that § 316(e) does not permit placing the burden of persuasion on the patent owner. Based on the requirements outlined in §§ 311-13, the petitioner defines the scope of the IPR through the petition, similar to how a plaintiff uses traditional pleadings to define the scope of litigation before federal courts. These sections make clear that amendments do not create a “new” claim for the Board’s consideration; they merely respond to at least one ground of unpatentability' originally raised by the petitioner. Sections 314 and 316, when read together, explain that the patent owner may use amendment as a tool to narrow claim scope in an effort to ensure its patentable subject matter remains properly protected. The provision of the AIA relating to the estoppel effect of IPRs, § 315(e), is consistent with the remainder of the statute only if the petitioner bears the burden to prove its propositions of unpatentability for all claims. And, §§ 316(d)(2) and 317, in combination, contemplate the use of amendments as a settlement tool, indicating that Congress contemplated narrowing amendments which would relieve a petitioner of any threat of infringement, while allowing the patent, as amended, to survive. When read in conjunction with the directive of § 318, we believe that the Board must assess the patentability of all claims in the proceeding, including amended claims that have been entered into the proceeding after satisfying the requirements outlined in § 316(d), and must do so through the lens of § 316(e). i. Petitioner Controls the Scope of the IPR: §§ 311-13 Section 311(a) provides that a person “not the owner of a patent” may file a petition to institute an inter partes review. 35 U.S.C. § 311(a). Section 311 also limits the scope of the proceeding to grounds that “could be raised under section 102 or 103 and only on the basis of prior art consisting of patents or printed publications.” Id. § 311(b). Section 312 sets forth the various statutory requirements to which each petition challenging the validity of a patent must conform before the PTO may institute an inter partes review. Id. § 312(a) (“A petition filed under section 311 may be considered only if—” (emphasis added)). The petition must identify, “in writing and with particularity, each claim challenged, the grounds on which the challenge to each claim is based, and the evidence that supports the grounds for the challenge to each claim ....” Id. § 312(a)(3). This provision confirms that the petitioner, not the patent owner, controls the scope of the IPR. The language of § 311 and § 312 tracks the language of § 316(e)—all reference the “grounds, or propositions of unpatentability” that carry throughout the proceeding. Section 313 further explains that the patent owner has the right, but not the obligation, to file a preliminary response to the petition. Id. § 313 (“[T]he patent owner shall have the right to file a preliminary response to the petition .... ” (emphasis added)). This provision makes sense in context because the patent owner has no burden to overcome a petitioner’s assertions. Given the statutory and regulatory requirements for amending claims in an IPR, amendments cannot and do not create new and different claims for consideration. Amendments cannot add new claim scope or new matter; they are in fact prohibited from doing so by the requirements of § 316(d). And, per the PTO’s regulatory requirements in Rule 42.121, proposed amended claims must respond to a ground of unpatentability raised by the petitioner and upon which the IPR was instituted. The ground must carry through the entire proceeding; otherwise, amendments adding limitations to the challenged claims to “overcome” an asserted challenge would make no sense. ii. Institution: § 314 Relevant to this appeal, § 314(a) explains that the Director must determine that “there is a reasonable likelihood that the petitioner would prevail with respect to at least 1 of the claims challenged in the petition,” based on the petition and any patent owner response under § 313. 35 U.S.C. § 314(a). It is only after the institution decision that the patent owner may elect to adjust the scope of its patent grant by proposing narrowing amendments to protect its patentable subject matter. In this way, IPR functions as a process for refining and limiting patent scope, similar to the inter partes reexamination process. See Cuozzo, 136 S.Ct. at 2144. iii. Application of Estoppel to IPRs: § 315 Section 315 describes how an IPR interacts with other patent-related proceedings, including examination, administrative review, and federal court litigation. Section 315(e) provides that, where institution occurs and the proceeding results in a final written decision under § 318(a), the petitioner, real-party in interest, or privy of the petitioner are all estopped with respect to “any ground that the petitioner raised or reasonably could have raised during that inter partes review” against that claim. 35 U.S.C. § 315(e). This provision is only consistent with the remainder of the AIA if the petitioner bears the burden to prove all propositions of unpatentability. Where the petitioner bears the -burden, it is logical to estop the petitioner from raising that ground in the future, whether related to originally challenged claims or entered amended claims. If the patent owner were to bear the burden to demonstrate the patentability of proposed amended claims and to do so by reference to prior art not addressed in the IPR, it would be illogical to say that the petitioner is thereafter estopped from anything as to those claims. iv. The Impact of Settlements: §§ 317-18 Section 317, the section of the statute immediately following Congress’s express statement in § 316(e) regarding the proper burden of persuasion for all claims, contemplates, in conjunction with the opportunity for additional uncontested amendments under § 316(d)(2), the possibility that the amendment process will be used as a settlement tool in IPRs. This too makes sense; a petitioner in an IPR may decline to maintain a challenge to a narrower amended claim if the patent owner agrees not to seek to enforce any claim scope broader than the scope of the proposed amendment. The first sentence of § 317(a) states that the PTO must terminate the participation of a particular petitioner, in a particular IPR, based on the filing of a joint motion and settlement by that petitioner and the patent owner. At that point, either (1) the patent owner is the only party remaining in the IPR, and the PTO can terminate the review or proceed to a final written decision as described in § 318(a); or (2) other petitioners are still participating in the IPR, and the IPR moves forward as usual. If a settlement occurs and the IPR is terminated, no certificate incorporating the amendment into the patent ever issues. Section 318(b) makes clear that no certificate either reaffirming a challenged claim or substituting an amended claim for a challenged one issues unless and until the Board chooses to issue a final judgment under § 318(a) in which it'assesses the patentability of both categories of claims. In the absence of a final written decision, the patent survives as originally written, subject to any narrowing agreements or covenants not to sue between the original parties. And, it survives subject to any later IPR or court challenges it might face. The final sentence of § 317(a) gives the Board the option to proceed to final judgment in any proceeding where the original petitioners choose not to continue their challenge. The Board might do this for any number of reasons. For example, the Board may decide that the showing of unpatentability with respect to the challenged claims is so strong that the public is better served by a cancellation of those claims; it may decide that even the narrower, amended claims are unpatentable in the face of the prior art on which the IPR was predicated and that confirmation of that fact is important; or it may decide that the amended claims are patentable in the face of the prior art challenges precisely because they are narrower than the original claims, and that it is important for the patent to be amended to reflect that fact so the public can benefit from that narrowing. Should the Board elect to continue to a final written decision in this scenario, § 318(a) requires the Board to undertake a patentability analysis on all original and amended claims in the proceeding. Thus, it is at that point, and not earlier, that the statute contemplates consideration of an amended claim’s patentability. As the Supreme Court recognized in Cuozzo, where the challenger ceases to participate in the IPR and the Board proceeds to final judgment, it is the Board that must justify any finding of unpatentability by reference to the evidence of record in the IPR. See 136 S.Ct. at 2144. This accords with traditional requirements of agency adjudication under the APA. There is no reason dictated by either the language or the logical structure of the statute, or by Cuozzo’s recognition of the Board’s obligations when a petitioner absents itself from an IPR, to conclude that this burden does not apply equally to amended claims. Indeed, as we noted before, the language in § 318(a) mirrors that of § 316(e). v. The Overall AIA Framework Read in their entirety and collectively analyzed, the statutory provisions of the AIA lay out an internally consistent, logical, and unambiguous structure for the conduct of IPRs. Understanding the statutory structure in this way is consistent with the concept that “inter partes review helps protect the public’s ‘paramount in-' terest in seeing that patent monopolies ... are kept within their legitimate scope.’ ” Cuozzo, 136 S.Ct. at 2144 (quoting Precision Instrument Mfg. Co., 324 U.S. at 816, 65 S.Ct. 993). There is a legitimate scope for properly-crafted patent protection. The goal underlying the AIA is twofold: (1) eliminating patents that foster abusive litigation; and (2) affirming and strengthening viable patents. The legislative history reflects these dual objectives. As early as 2006, Senator Leahy explained that the AIA: [I]s not an option but a necessity. ... I also want to ensure the delicate balance we have struck in the post-grant review process and make certain that the procedure is both efficient and effective at thwarting some strategic behavior in patent litigation and at promoting a healthier body of existing patents. 152 Cong. Rec. 16834 (2006) (statement of Sen. Leahy on S. 3818) (emphasis added). Allowing narrowing amendments during an IPR helps strengthen and clarify patents. As the PTO itself testified before Congress, providing a patent owner with a meaningful opportunity to amend subject to minimal statutory and regulatory criteria helps “preserve the merited benefits of patent claims better than the win-all or lose-all validity contests in district court.” PTO Gen. Counsel Toupin Statement, at 10. The AIA achieves these dual goals through a defined mechanism allowing for a limited category of challenges—an adversary proceeding where the Board is the arbiter of, rather than a party to, challenges asserted under only § 102 and § 103 of Title 35. The AIA relies on the adversarial nature of IPRs to ensure quick but thorough adjudication of the merits: the petitioner raises its best arguments at the outset; the patent owner has the opportunity to adjust the scope of its claims if need be; and the Board provides a speedy ruling as to the patentability of the original and amended claims. d. Legislative History of § 316(e) While legislative history generally carries little weight when interpreting the text of issued statutes, “[w]hen aid to construction of the meaning of words, as used in the statute, is available, there certainly can be no rule of law which forbids its use, however clear the words may appear on superficial examination.” Train v. Colo. Pub. Interest Research Grp., Inc., 426 U.S. 1, 10, 96 S.Ct. 1938, 48 L.Ed.2d 434 (1976). The clarity' of the statutory provision here, both alone and in context, obviates the need to rely on the legislative history of the AIA. The legislative history nevertheless strongly supports our conclusion that the language of § 316(e) unambiguously places the burden of proving the unpatent-ability of all claims on the petitioner. As noted, Congress made clear that patent owners may propose amendments to their patents as of right at least once in an IPR. The congressional record reflects Congress’s desire to protect the patent owner’s right to propose amendments by placing the burden of proving the unpa-tentability of amended claims entered into an IPR on the petitioner. Earlier drafts of § 316(e) stated that “[t]he presumption of validity in § 282 shall apply in post-grant review proceedings.” PTO Suppl. Br. 20 (emphasis in original) (quoting S. 3600, 110th Cong. § 5(c) (2008) (proposing 35 U.S.C. § 331(a)). These drafts also stated that “[t]he petitioner shall have the burden of proving.a proposition of invalidity ... S. 3600, 110th Cong. § 5(c) (2008) (emphasis added) (proposing 35 U.S.C. § 33103)); see also S. 1145, 110th Cong. § 5(c)(1) (2008) (proposing 35 U.S.C. § 331(b) (“The petitioner ... shall have the burden of proving a proposition of invalidity .... ” (emphasis added)))