[This is a draft of an article in The Dictionary of Eighteenth Century German Philosophers, 3 vols., edited by Manfred Kuehn and Heiner Klemme (London/New York: Continuum, 2010).]
Johann (Friedrich) Schultz (also: Schulz/Schulze) was born on 11 June 1739 in Mühlhausen (Polish: Gwardejskoje), East Prussia, a town south and a little east from Königsberg, and died 27 June 1805 in Königsberg, where he was a professor of mathematics at the university. Apart from some original work in mathematics, he is best known as a colleague and trusted expositor of Immanuel Kant.
Schultz attended the Collegium Fridericianum in Königsberg, then matriculated at the university on 24 September 1756 — a year after Kant arrived as a lecturer — and studied theology and mathematics. Ludwig Borowski [bio] was attending Kant’s lectures during these years and he claimed (in 1804) that Schultz was one of Kant’s best students (alongside C. J. Kraus, J. G. K. C. Kiesewetter, Marcus Herz, and J. F. Gensichen). This claim is often repeated in the literature, but Schultz explicitly denies having ever attended Kant’s lectures, “except for a single hour of physical geography, as a guest” (Reicke 1860, 42; Borowski is qtd. on p. 31).
Schultz worked as a private tutor in the Königsberg area before receiving a pastoral appointment in Starkenberg (1766-69), and then Löwenhagen (1769-75), returning to Königsberg in 1775 to serve as deacon at the Altroßgarten church. He also received at this time his magister degree from the university (6 July 1775), habilitating a month later (2 August 1775) with a disputation on acoustics, and he began offering lectures with the winter semester of 1775/76. The following year he was made the second court chaplain (or Hofprediger, the common title for him) at the castle church, where Johann Ernst Schulz [bio], a professor of theology at the university, was the first court chaplain (or Ober-Hofprediger). These two individuals are occasionally confused in the literature.
Kant was serving as rector when the academic senate recommended Schultz’s appointment as professor of mathematics to the government on 11 August 1786, shortly after the death of the previous professor of mathematics, Kant’s old rival Friedrich Johann Buck [bio]. (Sixteen years earlier, Kant had engineered Buck’s transfer from the chair of logic and metaphysics to the mathematics chair, so that Kant himself could assume Buck’s old position.) Schultz’s inaugural dissertation (15 February 1787) was again on acoustics. As professor of mathematics he was required to offer one set of public lectures each semester: arithmetic and geometry in the summer, and trigonometry and astronomy in the winter. Other than two exceptions (a set of metaphysics lectures during his second semester of teaching, and a course of public lectures on pedagogy that the philosophy professors took turns offering and that Schultz taught once in the summer of 1789), Schultz lectured exclusively on pure and applied mathematics: arithmetic, geometry, trigonometry, algebra, finite and infinite analysis, astronomy, mechanics, optics, etc., using Wolff’s popular mathematics text for most courses, Euler’s text for algebra, and his own texts, once they were published, for arithmetic, geometry, and trigonometry. (Suggestions that he lectured on Kant’s Religion within the Bounds of Unaided Reason [writings] confuse him with the theology professor, Johann Ernst Schulz.)
Schultz befriended the young J. G. Fichte [bio] during Fichte’s first visit to Königsberg (July to October 1791), and helped him procure a teaching position near Danzig. Fichte wrote of Schultz that “he has an angular Prussian face, but honesty and kindness shine forth from it,” and they remained in correspondence after Fichte’s departure (Fichte also discusses Schulz at some length in the 2nd Introduction  to his Wissenschaftslehre). This relationship was likely complicated by the fact that Schultz’s wife, Johanna Eleonore, née Büttner (1751-1795), became romantically attached to Fichte, precipitating his hasty retreat from Königsberg.
Schultz published poetry in his early years, as well as several Latin tracts on theology (1787, 1791), but the bulk of his literary efforts were concerned with mathematics, and with the explanation and exploration of Kant’s new critical system. Schultz’s mathematical writings include several successful textbooks (Foundation of Pure Mathematics, 1790; Brief System of Mathematics, 1797, 1805, 1806), but of most interest is his work on the parallel lines postulate (1780, 1784, 1786) and an essay on infinity (1788), which was an entrant for the 1786 Berlin Academy prize essay question asking for a “clear and precise theory of mathematical infinity”; although unsuccessful, this essay anticipated certain features of Cantor’s theory of transfinite numbers (Schubring 1982). The work on parallel lines was similar to that being done by many other mathematicians at the time (such as Karsten, Klügel, and Lambert) and that eventually resulted in the development of non-Euclidean geometries.
Correspondence between Kant and Schultz (fifteen extant letters in all) is primarily filled with strategizing against Kant’s critics; aside from that, a few topics discussed were Schultz’s claim of a redundancy in Kant’s table of categories (letters of August 1783 and February 1784; AA 10: 348-54, 366-68) and Kant’s insistence (against Schultz) that arithmetic was synthetic (25 November 1788; AA 10: 554-58). A comparison of Schultz’s 1790 review of Eberhard, and Kant’s draft for the same, also shows them disagreeing on space — Schultz, but not Kant, believing that geometry required an actually infinite space (AA 20: 418). During a visit to Königsberg in the summer of 1798, J. F. Abegg described Schultz as a Kantian of “strict observance,” a “childish admirer” who admonishes others (viz., his colleague Pörschke [bio]) for any deviation from the Kantian line; but Schultz in fact displayed considerable independence of mind and a critical attitude toward central features of Kant’s new philosophy.
Kant’s awareness of Schultz appears to have stemmed from his review of Kant’s 1770 inaugural dissertation [writings], when Schultz was still a pastor in Löwenhagen. Three months later, in a letter to Marcus Herz [bio], Kant referred to Schultz as “the best head for philosophy that I know in this region” (21 February 1772; AA 10: 133). His favourable opinion of Schultz endured, and thirty-five years later, in his open letter to J. A. Schlettwein [bio], Kant designated Schultz as his philosophical representative, “whose book on the critical system, entitled Prüfung, etc., should be examined by Herr Schlettwein” (29 May 1797; AA 12: 367-68) [writings]. An effect of this blessing on Schultz can be seen in a letter to Kant from Christian Weiß (25 July 1797; AA 12: 185-86), who until then had considered Fichte as Kant’s proper interpreter.
Schultz’s review of Kant’s Dissertation [writings] was published in two issues of a Königsberg periodical in November 1771. He praised the dissertation as “announcing a new epoch for metaphysics,” but also noted crucial difficulties. Specifically, Schultz worried about three claims made by Kant: (1) that humans lack intellectual intuition, (2) that space and time are forms of the sensible world, and (3) that there is only one world. Schultz noted that the entire dissertation depends on the first claim, yet it appears to be unprovable, and our own self-awareness suggests a counter-example. The second claim, even if successfully proved, required an additional proof that space and time were not also applicable to the intelligible world (this point re-appears in later criticisms of the Critique of Pure Reason [writings], viz., by H. A. Pistorius [bio], J. G. Maaß and, in the nineteenth century, by Adolf Trendelenburg). Finally, Schultz rejected the argument for the third claim altogether; Kant’s demonstration that all substances must share a common cause in order to stand in reciprocal interaction did not exclude the possibility that wholly separate worlds could exist that stem from this same cause. Despite these significant criticisms, Kant wrote in his letter to Herz that Schultz “has grasped the points of the system very well” (AA 10: 133), and felt that he could answer Schultz’s worries.
Given Kant’s praises of Schultz, one might think Schultz would have been among the first to receive a copy of the Critique upon its publication, or perhaps be consulted during its writing, but neither was the case. In a letter to Herz (11 May 1781; AA 10: 268-70), Kant wrote that he was pinning his hopes for being understood on Mendelssohn [bio], Tetens [bio], and Herz. Only after receiving disappointing news from these quarters did Kant send a copy of his book to Schultz (3 August 1781) with a brief letter referring to Schultz’s review of the 1770 Dissertation and asking if he might look over the new book and evaluate it. It took Schultz two years to respond (they might have discussed things in person, of course, but the content of the letters suggests otherwise), and the ensuing correspondence resulted in Kant convincing Schultz to publish his review “as an independent piece, so as not to be buried among the mass of reviews of other sorts” (Kant to Schultz, 22 August 1783). This would also free the work from the publishing vagaries of periodicals, widen the potential audience, and allow Schultz to expand his discussion (Kant to Schultz, 26 August 1783).
The resulting Elucidation (Erläuterungen, 1784) was to have three parts: (1) a sketch of Kant’s Critique, (2) hints for understanding it (among other things, Schultz argued that Kant overcame the anti-metaphysical and anti-religious scepticism of Hume and provided a solid ground for morality and the Christian religion), and (3) an evaluation of the system as such. Lack of time caused him to postpone this third part, eventually published as his Examination (Prüfung, 1789, 1792). The Elucidation was discussed in four reviews, and at great length in the Allgemeine deutsche Bibliothek by H. A. Pistorius [bio], who viewed it as the authorized commentary on “the most important work of metaphysics since the time of Aristotle.”
Schultz nevertheless maintained serious reservations regarding Kant’s philosophy, as was evident from his review of a 1785 metaphysics textbook published by the Jena professor J. A. H. Ulrich [bio]. Ulrich had hoped Kant would review the book (21 April 1785; AA 10: 402), but Kant passed this task on to Schultz. Among other things, Ulrich tried to reconcile Kant and Leibniz, argued that the Critique should not limit knowledge to objects of possible experience, and questioned whether the table of categories was exhaustive. Schultz’s review of Ulrich was remarkably sympathetic: “he found his own doubts reflected in many of the author’s doubts” and noted that these doubts “directly concern the main foundation of the entire Kantian doctrine and that the latter, no matter how much it contains of what is excellent, important, and indubitably certain, does not yet carry the sort of apodictic conviction that would be necessary to an unrestricted acceptance of what is really its main purpose.” Schultz regretted that Ulrich had not examined the transcendental deduction more carefully, since it lies at the very heart of Kant’s system, but that “perhaps it was only its obscurity that prevented him from doing so, an obscurity that occurs primarily here, in this part of the Critique that should be the clearest, if the Kantian system is to afford complete conviction.” Schultz closed by suggesting an equivocation in Kant’s use of ‘experience’: sometimes he seems to mean a judgement of perception (a subjective empirical judgement valid only for me) and other times a judgement of experience (an objective empirical judgement valid for everyone); if it is the former, then the deduction appears to be false, if the latter, then it is trivial.
Kant was understandably upset by this review, but it motivated him to re-write the deduction for his second edition of the Critique (1787) — see also Kant’s long note to the preface of the Metaphysical Foundations of Natural Science [writings], where he publicly answers Schultz (AA 4: 474-76), in part by demoting the transcendental deduction.
Like his colleague C. J. Kraus [bio] in Königsberg, and K. L. Reinhold [bio] in Jena, Schultz was enlisted by Kant to write book reviews on his behalf, and his review of Eberhard (1790) incorporated material that Kant himself had drafted (see their correspondence from June and August of 1790, AA 11: 182-84, 200-1). This came on the heels of Kant’s own public response to Eberhard in his On a Discovery (1790) [writings]. Schultz’s service to Kant was crowned by his two-volume Examination (1789, 1792), a work publicly acknowledged by Kant as the definitive account of his philosophy.
(anon.), Review of Kant’s Inaugural Dissertation, in the Königsbergsche Gelehrte und Politische Zeitungen (November 22-25, 1771). Reprinted in Reinhard Brandt (op cit.), pp. 59-66. Transl. by James C. Morrison (op cit.), pp. 163-70.
Vorläufige Anzeige des entdeckten Beweises für die Theorie der Parallellinen (Königsberg, 1780). 2nd ed.: 1786.
Entdeckte Theorie der Parallelen, nebst einer Untersuchung über den Ursprung ihrer bisherigen Schwierigkeit (Königsberg: D. C. Kanter, 1784).
Erläuterungen über des Herrn Professor Kant Critik der reinen Vernunft (Königsberg: C. G. Dengel, 1784). 2nd ed.: 1791. Transl. by James C. Morrison (op cit.), pp. 3-141.
(anon.), Review of J. A. H. Ulrich, Institutiones logicae et metaphysicae scholae suae scripsit (Jena: Cröker, 1785), in Allgemeine Literatur-Zeitung (December 13, 1785), pp. 247-49. Translated into English in Brigitte Sassen, tr. and ed., Kant’s Early Critics (Cambridge: Cambridge University Press, 2000), pp. 210-14.
Darstellung der vollkommenen Evidenz und Schärfe seiner Theorie der Parallelen (Königsberg: G. C. Hartung, 1786).
Prüfung der Kantischen Critik der reinen Vernunft, 2 vols. (Königsberg: Hartung, 1789; Nicolovius 1792). Reprinted in Aetas Kantiana, 1968.
Betrachtungen über den leeren Raum (Königsberg, 1758).
De geometria acustica seu solius auditus ope exercenda (Königsberg, 1775).
De geometria acustica nec non de ratione 0:0 seu basi calculi differentialis (Königsberg, 1787).
Elementa theologiae popularis theoreticae (1787).
Versuch einer genauen Theorie des Unendlichen (Königsberg: G. L. Hartung, 1788).
Review of Immanuel Kant, Metaphysische Anfangsgründe der Naturwissenschaft (Riga, 1786; 2nd ed: 1787), in Allgemeine Literatur-Zeitung (August 24-25, 1789), cols. 537-52.
Review of J. A. Eberhard, ed., Philosophisches Magazin (Halle), vol. 2, no. 1-4, in Allgemeine Literatur-Zeitung (September 24-27, 1790), cols. 785-814. Reprinted alongside drafts in Kant’s hand at AA 20: 385-423.
Anfangsgründe der reinen Mathesis (Königsberg: Hartung, 1790).
Elementa theologiae practicae (1791).
Vertheidigung der kritischen Briefe an Herrn Emanuel Kant über seine Kritik der reinen Vernunft, vornehmlich gegen die Bornischen Angriffe (Göttingen: Vandenhoek und Ruprecht, 1792).
Kurzer Lehrbegriff der Mathematik (Königsberg: Nicolovius, 1797, 1805, 1806). Part One: Kurzer Lehrbegriff der Arithmetik, Geometrie, Trigonometrie und Landmesskunst; Part Two: Kurzer Lehrbegriff der mechanischen und optischen Wissenschaften; Part Three: Populäre Anfangsgründe der Astronomie.
Sehr leichte und Kurze Entwickelung einiger der wichtigsten mathematischen Theorien (Königsberg: F. Nicolovius, 1803).
Anfangsgründe der reinen Mechanik, die zugleich die Anfangsgründe der reinen Naturwissenschaft sind (Königsberg: F. Nicolovius, 1804).
ADB, vol. 32, p. 716-17 (Otto Liebmann).
Allison, Henry, The Kant-Eberhard Controversy (Baltimore: Johns Hopkins University Press, 1973).
APB, vol. 2, pp. 646 (Fritz Gause).
Brandt, Reinhard, “Materialien zur Entstehung der Kritik der reinen Vernunft (John Locke und Johann Schultz).” In: Beiträge zur Kritik der reinen Vernunft, 1781-1981, ed. by Ingeborg Heidemann and Wolfgang Ritzel (Berlin: Walter de Gruyter, 1981), pp. 37-68.
Hamberger/Meusel (1798), vol. 7, pp. 361-62; (1806), vol. 12, p. 381.
Koriako, Darius, Kants Philosophie der Mathematik (Hamburg: Felix Meiner Verlag), pp. 279-82.
Kuehn, Manfred, Kant: A Biography (New York: Cambridge University Press, 2001), pp. 125, 194, 268-69, 321-22.
Landau, Albert, Rezensionen zur kritischen Philosophie, 1781-87 (Bebra: Albert Landau Verlag, 1991).
Martin, Gottfried, Arithmetik und Kombinatorik bei Kant (Berlin, de Gruyter, 1972).
Metzger, Johann Daniel, Über die Universität zu Königsberg (Königsberg: Gottlieb Lebrecht Hering, 1804), pp. 65-6.
Morrison, James C., Johann Schultz, Exposition of Kant's Critique of Pure Reason (Ottawa: University of Ottawa Press, 1995).
Munegato, Cristiana Bonelli, Johann Schultz e la prima recezione del criticismo kantiano (Trento: Verifiche, 1992).
Reicke, Rudolf, Kantiana. Beiträge zu Immanuel Kants Leben und Schriften (Königsberg: Th. Theile, 1860).
Schubring, Gert, “Ansätze zur Begründung theoretischer Terme in der Mathematik: Die Theorie des Unendlichen bei Johann Schultz (1739-1805).” In: Historia Mathematica, 9 (1982): 441-84.
Stark, Werner, “Kant und Kraus: Eine übersehene Quelle zur Königsberger Aufklärung.” In: Reinhard Brandt and Werner Stark, eds., Neue Autographen und Dokumente zu Kants Leben, Schriften und Vorlesungen (Hamburg: Felix Meiner, 1987), pp. 165-200.
Theis, Robert, “Der ‘wackere Pastor Schultz’ und Kant. Ein Beitrag zum Frühkantianismus in Königsberg.” In: Joseph Kohnen, ed., Königsberger Beiträge: Von Gottsched bis Schenkendorf (Frankfurt/Main: Peter Lang, 2002), pp. 65-93.
Vorländer, Karl, Immanuel Kant: Das Mann und das Werk, 2 vols. (Leipzig: Felix Meiner, 1924), vol. 1, p. 254; vol. 2, pp. 32-4, 288.