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In re Prater (Prater I), 415 F.2d 1378, 159 U.S.P.Q. (BNA) 583 (C.C.P.A. 1968) (full-text), superseded by In re Prater (Prater II), 415 F.2d 1393, 162 U.S.P.Q. 541 (BNA) (C.C.P.A. 1969) (full-text).

Factual Background[]

At the time of their invention, the spectroscopic constituent analysis of gas mixtures entailed measurements leading to a system of simultaneous equations. Prater and Wei made the mathematical discovery that the most accurate results could be obtained by choosing for solution the subset of equations with the largest determinant. The number of possible solution subsets was very large 184,756 subsets for a ten-constituent gas mixture.[1] The application disclosed, as the "preferred embodiment" of the invention, an analog device for selecting and solving the appropriate subsets.[2] It was also disclosed that the invention could be practiced on a digital computer.[3] Both process and apparatus claims were drawn. The process claim was plainly readable upon mental, or pencil and paper, practice. So was the apparatus claim, considered apart from the rest of the specification, if a human being and his pencil and paper tools could be characterized as a "system."

The Patent Office attack on the application was therefore based on the "mental steps" doctrine, upon which was erected an edifice of objections under sections 101, 102, 103 and 112.[4]

Appellate Court Proceedings[]

Judge Smith, speaking for a unanimous court,[5] upheld both claims. His opinion commenced with a review of the origins and history of the "mental steps" doctrine, which he found to be of doubtful validity.[6] That conclusion can be considered dicta, however, as the process claim was sustained on the basis of three holdings sufficient to the outcome:

(1) "Patent protection for a process disclosed as being a sequence or combination of steps, capable of performance without human intervention and directed to an industrial technology a 'useful art' within the intendment of the Constitution is not precluded by the mere fact that the process could alternatively be carried out by mental steps.”[7]
(2) Cochrane v. Deener[8] cannot be read to require that statutory processes operate only upon materials; the relevant passage was dicta, spoken in the context of expanding, rather than confining, the category of patentable subject matter; and in any event, later Supreme Court cases upheld claims to processes acting on electrical phenomena.[9]
(3) The heart of an invention cannot be ignored when considering the questions of nonobviousness and anticipation just because it may be unpatentable subject matter when viewed in isolation.[10]

The court then held that the apparatus used to carry out the method of a valid process claim, when it is a "substantial apparatus counterpart" of that process, is also patentable.[11]

In sum, although the opinion did not reject the "mental steps" doctrine outright, it destroyed its utility as a basis for attacking program related patent applications. Because of that, the Patent Office petitioned for a rehearing of the case. It argued that the court had ignored both important issues and prior judicial holdings and that under the court's holding a patent would "confer upon a patentee the right to exclude others from thinking in a certain manner.”[12] The majority approved the petition without comment.[13] However, Judge Rich, joined by Judge Almond, dissented strenuously in a blistering criticism of the Patent Office's deportment and theories.[14] The legal effect of the decision to grant a rehearing was to nullify the opinion in Prater I; but Judge Smith's reasoning lived on, as later cases revealed.

On reargument, the Government added a new contention, namely, that a patent on this invention would control human thought processes and thus run afoul of the first, ninth, and tenth amendments to the Constitution.[15] Appellants responded, in essence, by repeating Judge Smith's subject matter discussion from his Prater I opinion.[16] The court considered these contentions without comment. The court characterized the "mental steps" doctrine and the decision in Cochrane in the same terms as the preceding opinion,[17] but on this occasion these comments were merely obiter dicta, since the process claims were rejected for failing to comply with Section 112.[18] Specifically, the court held that the process claims were readable upon non-machine practice, and since the appellants had admitted that they did not intend to cover such practice, they had failed to distinctly claim what they regarded as their invention.[19]

Upholding the apparatus claim, the court reiterated its holding in Prater I that subject matter unpatentable in its own right could distinguish an invention from the prior art.[20] In addition, it held that means-plus-function claims were to be read in light of the remainder of the specification and that the disclosure of an analog device (and perhaps the possibility of digital computer practice) limited the claims to machine implementation.[21]

It was also significantly stated in dicta that:

No reason is now apparent to us why, based on the Constitution, statute, or case law, apparatus and process claims broad enough to encompass the operation of a programmed general purpose digital computer are necessarily unpatentable. In one sense, a general purpose digital computer may be regarded as but a storeroom of parts and/or electrical components. But once a program has been introduced, the general purpose digital computer becomes a special purpose digital computer (i.e. a specific electrical circuit with or without electro mechanical components) which, along with the process by which it operates, may be patented subject, of course, to the requirements of novelty, utility, and nonobviousness. Based on the present law, we see no other reasonable conclusion.[22]

The broad sweep of that dicta was the primary reason that Judge Worley wrote a concurring opinion, rather than joining the majority:

It is questionable whether prior decisions denying patentability of purely mental steps, or the statute, read singly or together, can support a broad rule either sanctioning or prohibiting the patentability of such steps in relation to computer programs. Where the line will be drawn can only be determined on a case by case basis . . . .[23]

Judge Worley also took the occasion to deplore the possibility that Congress might modify the patent system "that has worked so well."[24]


  1. 415 F.2d at 1379, 159 U.S.P.Q. (BNA) at 585.
  2. Id. at 1380, 159 U.S.P.Q. (BNA) at 585.
  3. Id. at 1385-86, 159 U.S.P.Q. (BNA) at 590.
  4. Id. at 1381-82, 159 U.S.P.Q. (BNA) at 586-87.
  5. Chief Judge Worley concurred in the outcome but did not join in the opinion because he had not familiarized himself adequately with the issues. Id. at 1390, 159 U.S.P.Q. (BNA) at 593-94.
  6. Id. at 1385-89, 159 U.S.P.Q. (BNA) at 590-93.
  7. 415 F.2d at 1389, 159 U.S.P.Q. (BNA) at 593.
  8. 94 U.S. 780 (1876).
  9. 415 F.2d at 1387-89, 159 U.S.P.Q. (BNA) at 591-95.
  10. Id.
  11. Id. at 1389, 159 U.S.P.Q. (BNA) at 593.
  12. Id. at 1390-91, 160 U.S.P.Q. (BNA) at 231-32 (Rich, J., dissenting).
  13. Id. Judge Smith, the author of the first opinion, had died shortly before the opinion was handed down.
  14. Id. at 1390-93, 160 U.S.P.Q. (BNA) at 231-33 (Rich, J., dissenting).
  15. 415 F.2d at 1400 n.20, 162 U.S.P.Q. (BNA) at 547 n.20.
  16. Id. at 1400-01, 162 U.S.P.Q. (BNA) at 547-48.
  17. Id. at 1401-04, 162 U.S.P.Q. (BNA) at 548-50,
  18. 415 F.2d at 1405, 162 U.S.P.Q. (BNA) at 551.
  19. Id.
  20. Id.
  21. Id. at 1406, 162 U.S.P.Q. (BNA) at 551.
  22. Id. at 1403 n.29, 162 U.S.P.Q. (BNA) at 549-50 n.29 (emphasis in original).
  23. Id. at 1406, 162 U.S.P.Q. (BNA) at 552 (Worley, J., concurring)
  24. Id. at 1407, 162 U.S.P.Q. (BNA) at 552 (Worley, J., concurring).