concurring in part, dissenting in part, in which MAYER, Chief Judge, joins.
Technology has come to dominate modern industry and culture, and patent principles have evolved as a primary economic incentive for innovation. Our strength as a nation is grounded in our technologic leadership and entrepreneurial energy, and in our competitive vigor. The proper balance among invention, innovation, and competition is a matter of national concern. The doctrine of equivalents is part of that balance. The importance of the issue led the Federal Circuit and the Supreme Court to reconsider this body of long-established judge-made law.
The doctrine of equivalents was judicially created in order to preserve the value of patents as against imitators, described in Graver Tank as the “unscrupulous copyist.” 339 U.S. 605, 607, 70 S.Ct. 854, 94 L.Ed. 1097 (1950). The Court reaffirmed in Festo:
*1378If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying.
Festo Corf. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 731,122 S.Ct. 1831, 152 L.Ed.2d 944 (2002). The Court recognized that “the doctrine of equivalents renders the scope of patents less certain,” id. at 732, 122 S.Ct. 1831, and that “this uncertainty [is] the price of ensuring the appropriate incentives for innovation.” Id. In this context the Court, while rejecting the Federal Circuit’s imposition of an absolute bar to equivalency of amended claim elements, did not return to the status quo ante. Instead, in Festo the Court brought increased rigor to the es-toppels generated during patent examination.
A patentee’s access to infringement remedy under the doctrine of equivalents has long been subordinate to the estoppels that arise during examination. The patentee cannot reach, through equivalency, that which was disclaimed in order to obtain the patent. This requires judicial determination of what was yielded during examination, and its effect on particular alleged equivalents. The uncertainties of such determination has led to increasing constraints on application of the doctrine. In Festo the Court acted to limit access to equivalency in the circumstance when a claim, as initially presented by the applicant, had literally encompassed the device later alleged to be equivalent; when such claim was amended so that it no longer encompassed the alleged equivalent, the Court held that estoppel presumptively applies to the entire territory between the scope of the original proposed claim and the claim as amended. This presumption can be rebutted, but only on grounds “where the amendment cannot reasonably be viewed as surrendering a particular equivalent.” 535 U.S. at 740, 122 S.Ct. 1831.
Thus the Court tightened access to the doctrine of equivalents, for this presumption of surrender may arise even when the particular equivalent was not described in prior art, and even when the alleged equivalent was not a ground of rejection and was not disclaimed. When this presumption arises, rigorous criteria must be met for rebuttal. These criteria reflect the additional constraints that flow when the applicant had initially presented claims that included the now-alleged equivalent. My concern with the actions of this court on remand is with its interpretation and application of this new presumption and the Court’s rebuttal criteria.
The Court remanded, to this court and the district court, for application of these principles to Festo’s Carroll and Stoll patents, and specifically for determination of “what territory the amendments surrendered” and “whether petitioner can demonstrate that the narrowing amendments did not surrender the particular equivalents at issue.” Festo, 535 U.S. at 741, 122 S.Ct. 1831. My colleagues now implement the presumption of surrender in ways that enlarge the surrendered territory, and implement the rebuttal analysis by converting two of the Court’s three rebuttal criteria into questions of law and then deciding them, sua sponte, without trial or record. My colleagues deny Festo’s request to present evidence as to these issues despite their status as questions of first impression.
From this flawed implementation of the Court’s decision, I respectfully dissent.
I concur in the court’s ruling that determination of the presumption of surrender and its rebuttal is for the court and *1379is decided without a jury, by analogy to the decision in Markman v. Westview Instruments, Inc., 517 U.S. 370, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996). I also concur in the remand to the district court for determination of the rebuttal issue of un-foreseeability, although I object to the prejudgments with which the remand is encumbered. I do not agree with the treatment of the factual criteria of “tan-gentialness” and “other reasons” as questions of law, or with the adjudication of these new issues without permitting evidence and argument in accordance with the procedures of trial.
I
The doctrine of equivalents is not an end in itself. No patentee plans to rely on protection outside of the patent’s claims, as support for invention and investment. Disputed issues of equivalency generally arise only after an innovative advance has been successfully commercialized, and others appropriate the benefit thereof while skirting the claims. Thus the doctrine of equivalents is a tool of a technology-based economy; it is an indicator of the policy balance between creativity and imitation.
A national economic policy that weighs on the side of fostering development and investment in new technology will have a different approach to the law of equivalency than an economic policy aimed at facilitating competition by minor change in existing products. Any tightening or loosening of access to the doctrine of equivalents shifts the balance between inventor and copier. The high public interest in this case reflects these fundamentals, for the administration of this law affects major commercial and societal interests. The number and diversity of the amicus curiae1 briefs reflect the complexity of these concerns and the variety of viewpoints among technology-based enterprises. The public interest here is not in the fate of these litigants and these long-expired patents; the interest is in the way this judge made law affects technologic innovation and competition.
II
The Supreme Court remanded with instructions to determine, first, “what territory the amendments surrendered,” Festo, 535 U.S. at 741, 122 S.Ct. 1831, implementing the presumption of surrender that arises when a claim as originally filed covered the alleged equivalent, and was subsequently narrowed by amendment. The facts of the Carroll and Stoll patents raise several issues of first impression, questions whose resolution is fundamental to application of the Court’s new presumption.
For the Carroll reexamination patent, the only element for which equivalency is at issue is the claimed pair of sealing rings. The SMC devices use a single two-way sealing ring. The original Carroll patent claims, as filed and prosecuted and granted, did not include sealing rings or any other sealing element. The broadest claim of the original patent was:
1. A device for moving articles comprising a cylinder of non-ferrous material, a piston including a permanent mag*1380net having a pole-piece on each axial side thereof, a body disposed outside and adjacent to said cylinder, said body including a permanent magnet which substantially surrounds the cylinder, there being a pole piece on each axial side of the permanent magnet included in said body, and means for controlling the admission of pressure fluid into the cylinder and exhaust of fluid from the cylinder for moving the piston in the cylinder, the attractive forces between the permanent magnets being such that movement of the piston causes corresponding movement of the body below a predetermined load on the body and such that above said predetermined load movement of the piston does not cause corresponding movement of the body.
Festo requested reexamination in light of previously uncited German references, unrelated to the sealing rings element. With the reexamination application Festo presented new claim 9, that contained all the limitations of original patent claims 1, 2, 7, and 8, plus a clause to a pair of sealing rings:
a pair of resilient sealing rings situated near opposite axial ends of the central mounting member and engaging the cylinder to effect a fluid-tight seal therewith
During prosecution no rejection and no argument was directed to the sealing rings, although other elements of the claims were mentioned by the applicant and the examiner. No amendment was made to the sealing rings in the reexamination application.
The Court’s new presumption of estop-pel is founded on the premise that the patentee, by narrowing amendment, “disclaimed” a “material difference” between the claims before and after amendment. Festo, 535 U.S. at 734, 122 S.Ct. 1831, quoting Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126, 136-137, 62 S.Ct. 513, 86 L.Ed. 736 (1942). The presumption of surrender requires that the claims as originally presented covered the alleged equivalent and that the entire intervening territory was presumptively yielded by the amendment.
Festo argues that no territory with respect to the sealing rings was surrendered during prosecution. Festo points out that the sealing rings could not have been claimed more broadly because the only structure disclosed in the specification is the pair of sealing rings. Festo stresses the Court’s statement that “What is claimed by the patent application must be the same as what is disclosed in the specification; otherwise the patent should not issue.” 535 U.S. at 736, 122 S.Ct. 1831. The parties and the amici curiae recognized that there is a significant difference between claims that were initially of a scope that included the alleged equivalent and were narrowed by amendment that excluded the equivalent, and claims that did not include the equivalent and were not narrowed by amendment.
My colleagues hypothesize that Festo could have presented a claim to “at least one sealing ring,” and thus rule that the surrendered territory includes the accused SMC single sealing ring, although no such claim was requested. Festo points out that if such a claim had been presented for reexamination it would have been subject to rejection as new matter or for enlarged claim scope prohibited by 35 U.S.C. § 305. Judicial hindsight is not a basis for rewriting the prosecution record, and the points raised by Festo should not be ignored. The question of the scope of the presumptively surrendered territory is material to this remand, and to guide further application of the Court’s decision.
Related questions are present for the Stoll patent. The elements for which *1381equivalency is at issue are the pair’ of sealing rings and the sleeve of magnetizable material. In the Stoll application both of these elements were initially claimed, and the issue is the scope of the surrendered territory. Like the Carroll patent, these aspects are not adequately considered in the majority opinion.
The Stoll patent is the United States counterpart of a patent initially filed in Germany, and was filed as a translation of the German application. It contained claims in a dependent form that did not conform to United States practice. The relevant claims as initially filed follow, with emphases added to the elements for which equivalency is at issue:
1. A linear motor for use in a conveying system, said motor being operable by a pressure medium and comprising a tubular part connectible to a source of the pressure medium, a piston which is slidable in said tubular part and which has sealing means at each end for wiping engagement with an internal surface of the tubular part and so as to form a seal for the pressure medium, and a driven assembly which is slidable on the tubular part and which has means at each end for wiping engagement with an external surface of the tubular part, the piston and the driven assembly each carrying a drive magnet arrangement in the form of a hollow cylindrical assembly, each magnet arrangement having radial play relative to the adjacent surface of the tubular part, and surfaces of the magnet arrangements which face the tubular part being closely adjacent to the respective surfaces of the tubular part.
4. A linear motor according to any of claims 1 to 3, wherein the sealing means of the piston comprise sealing rings and the piston is provided with sliding guide rings, near the sealing rings.
8. A linear motor according to any of the preceding claims wherein the driven assembly is provided with a sleeve made of magnetizable material, which encircles the hollow cylindrical assembly of the magnet arrangement.
The Examiner- rejected all of the claims under § 112 ¶ 1, on the ground: “Exact method of operation unclear. Is device a true motor or magnetic clutch?” The Examiner also rejected claims 4-12 under § 112 ¶ 2 for improper multiple dependent form. No other rejection was made. In response Stoll changed “linear motor” to “an arrangement,” and rewrote the Claims. Stoll cancelled claim 1 and added claim 13 that included, inter alia, the elements of original claims 4 and 8:
13. In an arrangement having a hollow cylindrical tube and driving and driven members movable thereon for conveying articles, the improvement comprising wherein said tube is- made of a nonmagnetic material,
wherein said driving member is a piston movably mounted on the inside of said tube, said piston -having a piston body and plural axially spaced, first permanent annular magnets encircling said piston body,
said piston further including first means spacing said first permanent magnets in said axial spaced relation, the radially peripheral surface of said magnets being oriented close to the internal wall surface of said tube,
said piston further including plural guide ring means encircling said piston body and slidingly engaging said internal wall and
first sealing rings located axially outside said guide rings for wiping said internal wall as said piston moves along said tube to thereby cause any impurities that may be present in said tube to be pushed along said tube so that said *1382first annular magnets will be free of interference from said impurities,
wherein said driven member includes a cylindrical sleeve made of a magnetizable material and encircles said tube,
said sleeve having plural axially spaced second permanent annular magnets affixed thereto and in magnetically attracting relation to said first permanent annular magnets
and second means spacing said second permanent annular magnets in said axially spaced relation, the radially inner surface of said magnets being oriented close to the external surface of said tube,
said sleeve having end face means with second sealing rings located axially outside said second permanent annular magnets for wiping the external wall surface of said tube as said driven member is moved along said tube in response to a driving movement of said piston to thereby cause any impurities that may be present on said tube to be pushed along said tube so that said second permanent annular magnets will be free of interference from said impurities.
(Emphases added.) Claim 18 was allowed without rejection.
For the sealing rings, original claim 1 recited “sealing means” for the internal surface, original claim 4 claimed “sealing rings,” and new claim 13 claimed “first sealing rings.” Festo argues that the original claims, construed in light of the specification, do not include the SMC single two-way sealing ring. Festo also argues that since “sealing rings” were claimed in original claim 4, the territory surrendered between claim 4 and claim 9 does not include the single two-way sealing ring. The issue of the role of subordinate claims in determining the surrendered territory is raised by the parties, for although claim 1 is broader than claim 4, both were original claims. Resolution is necessary to this case.
For the sleeve of magnetizable material, a further variation arises. The sleeve of magnetizable material was claimed in original claim 8; its scope was not changed. Festo argues that since this element was originally claimed, and was never narrowed by amendment, no territory was surrendered. SMC argues that Stoll’s original claim 1 did not mention a sleeve of any material, and therefore that this scope was unlimited, and was narrowed when claim 1 was cancelled, despite the presence of original claim 8. Again, the question of the role of subordinate claims in determining the territory of surrender is squarely raised, and requires resolution.
It is improper simply to assume that all potential equivalents were surrendered in all cases, whatever the nature and scope of the original claims and whatever the relation of the amendment to the original claims. These aspects have wide implications, as the amici curiae recognized,2 and should not be decided by indirection and without discussion.
Ill
The Court held that to rebut the presumption of surrender the “patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the al*1383leged equivalent.” 535 U.S. at 741, 122 S.Ct. 1831. The Court identified three general classes of rebuttal criteria: (1) unforeseeability of the equivalent; (2) whether the reason for the amendment had only a tangential relation to the equivalent; and (3) some other reason why the patentee could not reasonably be expected to have retained literal coverage of the equivalent. Id. at 740-741, 122 S.Ct. 1831.
The patentee must establish that although the entire intervening territory was presumptively surrendered, the particular alleged equivalent was not surrendered. Festo states that it can meet the Court’s rebuttal criteria, and has proffered evidence as to all three criteria. This court now denies Festo the opportunity to present evidence as to the two criteria of tan-gentialness and some other reason, establishing these criteria as questions of law, not fact, and decides these questions of first impression without development and without evidence. As to these criteria, Festo has been deprived of both trial and appeal.
1. Unforeseeability
I concur in the remand for trial of the issue of unforeseeability, although I strongly object to the court’s inappropriate prejudgments of the facts on remand. For example, for the magnetizable sleeve, Fes-to states that it will present evidence that “one skilled in the art at that time of the application would not have foreseen the interchangeability of an aluminum alloy sleeve with the sleeve of magnetizable material in the STOL small gap design.” Festo proffers evidence of the technologic complexity and state of understanding of the subject matter, the context in which the amendments were presented, the content of the prior art, and the nature of the SMC equivalent material. My colleagues announce that it is “unlikely” that Festo can establish unforeseeability, because aluminum is a “commonly available metal.” However, the evidence on remand is entitled to be weighed at trial without this court’s thumb on the scale.
The court also rules that known equivalents cannot be unforeseeable, stating that any “alleged equivalent known in the prior art in the field of the invention, certainly should have been foreseeable at the time of the amendment.” This is not the holding of Pioneer Magnetics, Inc. v. Micro Linear Corp., 330 F.3d 1352 (Fed.Cir.2003), which the court cites as authority. In Pioneer Magnetics the court held that when the alleged equivalent was described in a reference that was cited during prosecution, and the narrowing amendment “was made to avoid the very prior art that contained the equivalent,” the equivalent thereby distinguished cannot have been unforeseeable. The Pioneer rationale was not that the equivalent technology was foreseeable because it was known, but that it was foreseeable because it had been specifically cited and disclaimed during prosecution. Those are not the facts of this case, for the amendments to the Carroll and Stoll patents were not made to avoid the SMC equivalents or to distinguish prior art that disclosed these equivalents.3
*1384This question of first impression should be remanded to the district court without encumbrance and without prejudgment, for appropriate exploration of the facts, and application of law to found facts. The parties are entitled to the opportunity to present evidence of this and the other criteria of rebuttal, in the context and with the safeguards of trial. See Icicle Sea-foods, Inc. v. Worthington, 475 U.S. 709, 714, 106 S.Ct. 1527, 89 L.Ed.2d 739 (1986) (for “findings of fact essential to a proper resolution of the legal question [the Court of Appeals] should have remanded to the District Court to make those findings”); Pullman-Standard v. Swint, 456 U.S. 273, 291-92, 102 S.Ct. 1781, 72 L.Ed.2d 66 (1982) (“[Factfinding] is the basic responsibility of district courts, rather than appellate courts, and ... the Court of Appeals should not have resolved in the first instance this factual dispute which had not been considered by the District Court.”) (quoting DeMarco v. United States, 415 U.S. 449, 450, 94 S.Ct. 1185, 39 L.Ed.2d 501 (1974)). (All alterations in original.)
2. Tangential Relation to the Reason for the Amendment
The Court ruled that there is no “call to foreclose claims of equivalence for aspects of the invention that have only a peripheral relation to the reason the amendment was submitted.” 535 U.S. at 738, 122 S.Ct. 1831. Rebuttal on this ground may arise, for example, when a claim was amended to distinguish a specific reference, and the amendment also excluded subject matter that was unrelated to the reference. Thus the reason why a claim was amended may be evidence of whether the alleged equivalent is sufficiently unrelated to the prosecution rationale as to rebut the presumptive surrender.
The court limits the evidence of this criterion to the prosecution record. However, the factors relevant to determination of tangential relation are unlikely to reside in the prosecution record, for unrelated subject matter or unknown equivalents are unlikely to have been discussed by either the examiner or the applicant. The issue of “tangentialness” may require consideration of how the reason for an amendment affected the patentee’s view that certain technology was extraneous. The prosecution record rarely discusses devices that are not prior art.
Festo and amici curiae have described various factors that may be relevant to the question of tangential or peripheral relation, such as the nature of the prosecution action, the content of any references that led to a narrowing amendment, and the differences between the claimed subject matter and the alleged equivalent. The example is offered that if the reason for an amendment were compliance with an en-ablement rejection, then it may be relevant whether the later-arising equivalent could be practiced without undue experimentation. Such evidence would not reside in the prosecution record.
Festo had not been informed that its evidence is limited to the prosecution record, upon which this court now decides the issue without Festo having had the opportunity to prove its case. At the trial prosecution history estoppel was not at issue; SMC told the district court that “this is not really a prosecution history estoppel case.” Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 72 F.3d 857, 863 (Fed.Cir.1995). Now that it is such a case, Festo is surely entitled to develop an evi-dentiary record. The court’s refusal to remand on this ground of rebuttal, ruling that evidence outside the prosecution record is not admissible, renders this rebuttal criterion unlikely ever to be met.
*13853. Some Other Reason
The Court’s third rebuttal criterion of “some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question” avoids foreclosing the opportunity of rebuttal in unanticipated situations. It is unnecessary to rule in advance that “some other reason” is narrowly limited to “shortcomings of language” and generally to the prosecution record. Like tangentialness, if some other reason arises that relates to the alleged equivalent, evidence would be more likely to reside outside of the prosecution record than within it.
The Court’s concern with language appears to be directed not to the simple meaning of words, but to the prescience of inventors as they explore new technology. Festo raises the argument that it “could not be expected to draft a claim to cover all insubstantial modifications an infringer may dream up;” indeed, this is a policy question of consequential impact on the content of patent specifications. Insofar as the “inadequacy of language” is considered as a ground of rebuttal, the subject engaged Judge Hand in Philip A. Hunt Co. v. Mallinckrodt Chemical Works, 177 F.2d 583 (2d Cir.1949), who observed that “obviously it is impossible to enumerate all possible variants. Indeed, some degree of permissible latitude would seem to follow from the doctrine of equivalents, which was devised to eke out verbal insufficien-cies of claims.” Id. at 585.
This court, however, approaches the criterion of “some other reason” from the opposite direction, ruling that it is necessary for Festo to show some reason that “prevent[ed] Stoll from describing the accused [aluminum] equivalent.” The court imposes the requirement that the inventor was actually prevented from describing an unknown equivalent, in order to rebut the presumption of surrender — and that the reason was contained in the prosecution history — a virtual impossibility.
All three classes of rebuttal raise questions of fact and all raise questions of first impression, requiring full and fair exploration of the issues with benefit of the procedures of trial. The court’s limitation of the presentation of evidence that may serve to rebut the presumption of surrender constricts judicial ability to render a just decision.
CONCLUSION
The Supreme Court in its Festo decision balanced the needs of patentees for adequate protection of their inventions, and the needs of would-be competitors for adequate notice of the scope of that protection. This court’s application of the Court’s decision in Festo places new and costly burdens on inventors, and reduces the incentive value of patents. By adopting a generous interpretation of the scope of surrender, and stinginess toward its rebuttal, the ensuing framework is one that few patentees can survive.
. Briefs were filed by the American Council on Education et al.; American Intellectual Property Law Ass’n; Association of the Bar of the City of New York; Association of Patent Law Firms; Bar Ass'n of the District of Columbia; Biotechnology Industry Org.; Car-gill, Inc. et al.; Consumer Project on Technology; Eli Lilly & Co.; Federal Circuit Bar Ass’n; Federation Internationale Des Conseils en Propriété Industrielle; Intel Corp.; Sterne, Kessler, Goldstein, & Fox, P.L.L.C.; the United States; and the Washington State Bar Ass’n.
. Various amicus briefs pointed out the complex implications for patent prosecution, for it is customary to present broad and successively narrow claims, to rewrite or cancel claims, and to move elements between dependent and independent claims. The amici pointed out that such routine actions may now have unforeseeable consequences, and impose new pitfalls, costs, and burdens on inventors.
. Several amici curiae pointed out the incongruity whereby equivalency in fact follows from known (foreseeable) interchangeability, see Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 25, 117 S.Ct. 1040, 137 L.Ed.2d 146 (1997) ("'An important factor is whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was.' ”) (quoting Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605, 609, 70 S.Ct. 854, 94 L.Ed. 1097 (1950)), yet the patentee must now prove un-foreseeability in order to gain access to the doctrine of equivalents.