concurring in the judgment.
I agree that it is appropriate to reverse the grant of summary judgment. I write separately lest the majority’s opinion be taken as new law with respect to the requirements for antedating a publication that would otherwise be a reference under 35 U.S.C. § 102.
Antedating a Reference
The court’s opinion states that a reference can be antedated only by prior reduction to practice, stating: “Of course, Loral would bear the burden of production to present evidence of its asserted actual reduction to practice prior to the filing date of its patent application.” The opinion also states that “at trial Toshiba and NEC would bear the burden of proving by clear and convincing evidence that the Erb reference was published prior to Loral’s reduction to practice.” However, the opinion correctly quotes precedent that the inventor “had to ‘come forward with evidence of an earlier date of invention.’ ” The date of invention is the date of conception, not the date of reduction to practice. Pfaff v. Wells Electronics, Inc., 525 U.S. 55, 60, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d 1641, 1644 (1998) (“The primary meaning of the word ‘invention’ in the Patent Act unquestionably refers to the inventor’s conception rather than to a physical embodiment of that idea.”); Id., at 66, 119 S.Ct. 304, 142 L.Ed.2d 261, 48 USPQ2d at 1646 (“petitioner’s argument *1366... does not persuade us that it is necessary to engraft a reduction to practice element into the meaning of the term ‘invention’ as used in § 102(b)”); Burroughs Wellcome Co. v. Barr Laboratories, Inc., 40 F.3d 1223, 1227-28, 32 USPQ2d 1915, 1919 (Fed.Cir.1994) (“Conception is the touchstone of inventorship, the completion of the mental part of invention.”)
Loral had to show that before the publication date of the Erb article the inventor, Dr. Amelio, had either a reduction to practice, or conception of the invention plus diligence to actual or constructive reduction to practice. This is well-established law, in the Patent Office as in the courts:
37 C.F.R. § 1.131(b) The showing of facts shall be such, in character and weight, as to establish reduction to practice prior to the effective date of the reference, or conception of the invention prior to the effective date of the reference coupled with due diligence from prior to said date to a subsequent reduction to practice or to the filing of the application....
The defendants readily concede that Dr. Amelio had conceived the patented invention before the publication date of the reference. Also, the evidence of activity constituting reduction to practice was not disputed by the defendants; their arguments were directed solely to the issues of corroboration and the position that the Erb date to be overcome was not the date of the article’s publication but the date when the underlying work was conceived and done. The interest of clarity of precedent, and efficiency on remand, require a more positive statement than has been made by my colleagues on this panel. Further, with the correction of the ruling that the work underlying the Erb article sets the date that must be antedated by Loral’s reduction to practice, there is no longer a disputed issue of fact that requires resolution on remand.
Corroboration
The court sets requirements of corroboration of the inventor’s testimony based on the law governing Patent Office interference practice, citing Cooper v. Goldfarb, 154 F.3d 1321, 47 USPQ2d 1896 (Fed.Cir.1998) and Lacotte v. Thomas, 758 F.2d 611, 225 USPQ 633 (Fed.Cir.1985), both PTO interferences, whose detailed and highly formalistic corroboration of the inventor’s work is traditionally required in order to establish priority between competing inventors. That is not at issue here. Here the issue is solely a matter of antedating a publication, where the probative value of the inventor’s testimony is as for any factual question: the weight and value of the evidence is determined, with due consideration to the issue to be decided as well as any contrary evidence and the burden of proof. The evidentiary standard for antedating a reference is not the same as the PTO requirement for establishing priority in an interference contest. Inventors’ affidavits have always been admissible to antedate a reference. The regulations are explicit that evidence to antedate a reference may be provided by the inventor:
37 C.F.R. § 1.131(a)(1) When any claim of an application or a patent under reexamination is rejected [on reference to] a printed publication, the inventor of the subject matter of the rejected claim ... may submit an appropriate oath or declaration to overcome the patent or publication. The oath or declaration must include facts showing a completion of the invention in this country ... before the date of the printed publication.
Antedating a reference is a common occurrence, governed by a stable and non-controversial jurisprudence. Let us not add uncertainties to this law.
*1367 The 102(g) Issue
The district court had required that Loral show an actual reduction to practice before the date of the underlying work of the Erb article, invoking § 102(g). See Loral Fairchild Corp. v. Victor Co. of Japan, No. 92-0128 (E.D.N.Y., June 21, 2000) slip op. at 8 (“This court, comparing the Erb work with the invention of the '674 patent, previously determined that the Erb work was prior art to the '674 patent.”); id. (“Beyond its finding of a lack of diligence, however, this court also determined that Messrs. Erb and Su conceived the invention before Dr. Amelio, the inventor of the '674 patent. Thus, the Erb/Su conception date predated publication of their article by more than a year.”); id. at 10 (“Loral has not proffered any new. evideneé to overcome this court’s finding, based on earlier reduction to practice, that the Erb work was prior art under 35 U.S.C. §§ 102(a) and 102(g).”) See also Loral Fairchild Corp. v. Victor Co. of Japan, 931 F.Supp. 1014, 1032 (E.D.N.Y.1996) (“[T]he record shows that Drs. Erb and Su actually reduced their process to practice at the end of September 1973.... Because Dr. Amelio cannot show reasonable diligence from before this date to his filing date, the Erb/Su work stands as prior art.”).
The record reflects a kind of inter partes interference proceeding with the authors of the Erb paper, who testified as to their work and when it was done. There is a specific statutory authorization for conducting an interference in the district court, but this does not apply when there is not an adverse claimant to a patent. Reliance on either the date of the Erb publication or the date of the work underlying the publication is mentioned in an ambiguous Footnote 1 in this court’s opinion, which flags the issue but does not lay it to rest. Much mischief can flow if we open this door whereby a publication is effective as a reference as of the date the authors did the underlying work. It is our obligation, as the reviewing court, to act to assure clarity in the law.