1 The Logicians of Kant’s School (Or, If Logic Has Been Complete Since Aristotle, What’s Left For a Logician To Do?) Jeremy Heis One of the most infamous claims in Kant’s Critique of Pure Reason concerns the completeness of formal logic: [S]ince the time of Aristotle [formal logic] has not had to go a single step backwards, unless we count the abolition of a few dispensable subtleties or the more distinct determination of its presentation, which improvements belong more to the elegance than to the secu- rity of that science. What is further remarkable about logic is that until now it has also been unable to take a single step forward, and therefore seems to all appearance to be finished and complete.1 (Bviii) This infamous claim was subject to severe criticism in the early part of the 19th century from figures as diverse as Bolzano, De Morgan, Hegel, and Fries.2 Of course, it is not surprising that figures such as these would be critical of Kant’s claim, since their conception of the scope and con- tent of logic differed fundamentally from his. What’s more surprising is that there arose starting already in the 1790s and into the 19th cen- tury a group of logicians who self-consciously thought of themselves as orthodox Kantians and who wrote extensive and original works in formal logic. Not only did these logicians show an affinity with Kant’s conception of logic, but their contemporaries and later logicians thought of them as forming a kind of school – what Friedrich Ueberweg, in his 1 Citations to Kant 1781/7 are according to the pagination in the first (“A”) and second (“B”) edition. Page references to Kant’s other works are to the pagination in the Akad- emie [Ak] edition: Kant 1902–. References to the body of Kant 1800 (The “Jäsche Logik” or JL) are frequently to paragraph (§) number. 2 Cf. Heis 2012, 95–7. Kant’s School 29 history of logic in the 19th century, calls the “logic of Kant’s school.”3 Ueberweg himself, who was very critical of the school, listed as members “Jakob, Kiesewetter, Hoffbauer, Maas, Krug, etc.” What made these logicians ‘Kantian’ is that they held to Kant’s conception of logic as formal. This distinctive conception of logic had four parts. First, formal logic was distinguished from transcendental logic. Second, formal logic was considered the science of thinking, not of cognizing. Third, it was asserted that formal logic abstracts from all relation to an object. Fourth, formal logic was held to be independent of psychology and metaphysics. Logicians in this school included Kant’s students, such as Schultz and Kiesewetter, but also later logicians who wrote after Kant’s death, such as Krug and Esser. Here is an undoubtedly incomplete list of some of the logicians in this Kantian school, along with some of their major works.4 Schultz, Johann. 1789. Prüfung der Kantischen Critik der reinen Ver- nunft. Vol. 1. Jakob, Ludwig Heinrich. 1791. Grundriss der allgemeinen Logik. 2nd ed. Kiesewetter, J.G.C. 1791. Grundriss einer allgemeinen Logik nach Kan- tischen Grundsätzen. Hoffbauer, J.C. 1792. Analytik der Urtheile und Schlüße. Maass, J.G.E. 1793. Grundriss der Logik. Kant, I. 1800. Logik. Ed. Jäsche. Krug, Wilhelm Traugott. 1806. Denklehre oder Logik. Herbart, Johann Friedrich. 1813. Lehrbuch zur Einleitung in die Philos- ophie. Zweiter Abschnitt. Die Logik. Esser, Wilhelm. 1823. System der Logik. Drobisch, Moritz. 1836. Neue Darstellung der Logik. 21851, 31863. Hamilton, William. 1860. Lectures on Logic. (Delivered 1837–8.) Mansel, Henry Longueville. 1851. Prolegomena Logica: An Inquiry into the Psychological Character of Logical Processes. 3 Cf. Ueberweg [1857] 1871, §29. 4 This list of logicians of Kant’s school is no doubt incomplete and open to debate. In putting together this list, I have more or less followed Ueberweg. In particular, among the German logicians, I list all of the logicians whom Ueberweg identi- fies as among “The Logic of Kant’s School.” This list admittedly omits logicians who plausibly belong, such as Mehmel and Krause. Ueberweg also lists other logi- cians whose works are “more or less related to this formal view-point”: Christian Twesten, Ernst Reinhold, Carl Friedrich Bachmann and Friedrich Fischer. I don’t discuss these “more or less related” works in this chapter, partly because my exper- tise is limited, and partly because I am trusting Ueberweg’s opinion that they depart in one way or the other from the conception of logic definitive of Kant’s school. To Ueberweg’s list, I have added the British logicians Hamilton and Mansel, for reasons I will shortly explain. One omission of note: I exclude Fries, since he does not hold the distinctly Kantian view that formal logic is independent of psychology (cf. Fries [1811] 1837, 4–5). 30 Jeremy Heis Not surprisingly, most of these logicians were German and wrote in the few decades after the publication of the first Critique. However, the last two logicians on the list were British, and that requires some explanation. But first some background about the history of logic in Britain in the early 19th century. In 1826, Archbishop Whatley ([1826] 1866) restored the fortunes of logic in Britain by arguing that logic is a science, not an art. As a science, logic contains a law, namely the dictum de omni et nullo, that explains the validity of the figures of the syllogism. And since logic is not an art, it’s not meant to be a tool of discovery, nor a “medicine of the mind.” Whately used this concep- tion of logic to defend logic against its detractors, who pointed to the alleged sterility and lack of utility of the study of logic. A few years later, William Hamilton defended Whately’s view of logic, but argued that in fact Whately’s point of view had already been expressed 50 years earlier by Kant in the Critique of Pure Reason. Hamilton ([1833] 1861) argued that Kant had already maintained that formal logic is a science; that the logical laws explain the validity of forms of inference; that, as a canon and not an organon, it is not a tool of discovery; and lastly, that it was not designed to cure errors in reasoning. These points about Kant’s conception of formal logic were captured in Kant’s dis- tinguishing formal logic from special logic and applied logic, respec- tively. Hamilton, having defended Kant’s conception of logic, in the following years lectured extensively on formal logic using the texts of the German Kantian logicians Krug and Esser. These lectures were for- mally published many decades later, after a wide circulation, in 1860 (cf. Hamilton [1860] 1874). Among Hamilton’s students was Henry Mansel, who wrote Prolegomena Logica in 1851, defending a kind of Kantian conception of formal logic. The very existence of a Kantian school seems surprising, since it’s not clear, from our point of view, what exactly the Kantian school took itself to be doing. After all, if logic has been complete since Aristotle, what’s left for a logician to do? In this chapter I want to answer this question. I’m going to identify four representative questions or issues that the logi- cians in this school considered and debated. In each case I’ll argue that this was a question that a reasonable reader of Kant might think Kant had left unsettled, and then I’ll give a representative sample of the kinds of answers that logicians in this school gave to these questions. My goal in this chapter is not to be exhaustive, but to introduce the reader to the kinds of questions, debates, and philosophy that were done by logicians in the Kantian school – a school that at least in the last century or so has been more or less absent from the historiography of logic. Since my goal in this chapter is to give the reader a sense of the questions asked by the Kantian logicians and to give the reader a sense of the kinds of answers that they gave, my goal in this chapter will not be to evaluate the answers given, either as interpretations of Kant or as philosophically Kant’s School 31 defensible positions in their own right. Though I will occasionally ed- itorialize, my goal here is simply to present the various views and not to evaluate them. I’ll identify four questions that the Kantian logicians attempted to answer. 1 What is the relationship between formal logic and analyticity? 2 What are the logical laws and how are they related? 3 What does it mean to say that logic is formal? 4 Are all concepts formed through comparison, reflection, and abstraction? I’ll address each of these questions in turn in the following four sections of this chapter. What Is the Relationship between Formal Logic and Analyticity? It’s clear from Kant’s characterizations of analytic judgments that ev- ery analytic judgment is meant to be knowable through logical laws alone. At various points he asserts that analytic judgments are “thought through identity” (A7/B10), that “their certainty rests on identity of con- cepts” (JL, §36), and that they are knowable through the principle of contradiction alone. For, if the judgment is analytic, whether negative or affirmative, its truth can always be adequately known in accordance with the principle of contradiction. The reverse of that which as concept is contained and is thought in the knowledge of the object, is always rightly denied. But since the opposite of the concept would contra- dict the object, the concept itself must necessarily be affirmed of it.