‘Left-Kantianism’ and the ‘Scientific Dispute’ between Rudolf Stammler and Hermann Cohen

1 Introduction

While in recent years interest in the neo-Kantian Marburg School has increased, research focusing on their legal and political philosophies is still rare. In cases where scholars do discuss the political side, we find the view that the proponents of the Marburg School defended a coherent view of ethical socialism. Thomas E. Willey argues that “Marburg neo-Kantian Socialism” was a “coherent intellectual movement” just before the First World War (Willey 1978, 116). Similarly, Frederick Beiser subsumes Rudolf Stammler, Franz Staudinger, Karl Vorländer, and Kurt Eisner under the umbrella term of “ethical socialism” without noticing that Stammler explicitly refrained from advancing an ethical foundation (cf. Beiser 2018, 2). However, this view does not correspond to the self-conception of the School’s members. Paul Natorp (1854–1924) thought that the differences between Hermann Cohen (1842–1918) and Rudolf Stammler (1856–1938) were so severe that he devoted an article to what he called their “scientific dispute” (Natorp 1913).

The Marburg School evolved during the peak of ‘historicism,’ a current concerned with the historicization of the conditions of knowledge.^[1] The neo-Kantian Marburg School’s ‘critical idealism’ seemed to counteract these developments. The most famous of its members, Cohen and Natorp, agreed on a Kantian a priori and ideal foundation of truth and morality. At the same time, however, they tried “to overcome the dualism between intuition and thinking and between matter and form” (Natorp 1986/1911, 65). They thought that rational thinking manifests teleologically. Instead of justifying definite a priori principles, they took scientific concepts and cultural norms as expressions of rationality, striving toward the unification of thought and belief systems. With their teleological approach to Kantian idealism, they were in line with the general trend of historicizing scientific knowledge and social norms.

Moreover, the School evolved during the “golden age of Marxism” (Kolakowski 1988, 11). Prussia was dealing with the consequences of the growth of industrialization and the crises of capitalism. The so-called worker’s question—the question of whether and how the situation of the workers could be improved—was a widely discussed topic among progressive, left, and conservative intellectuals alike. Right-wing conservative neo-Kantians, such as Jürgen Bona Meyer and Hermann von Helmholtz, believed that socialism was responsible for the allegedly moral and societal downfall of the late 1870s (Sieg 2013, 38–39). In contrast, the representatives of the Marburg School were convinced that an actualization of Kantian philosophy would lead to a justification of socialism. With a sensitivity to the historical nexus, the members of the school drew on Kant’s transcendental critique to work out a methodology that could engage with the inconsistencies of capitalism.

With their novel teleological approaches to Kant, new questions arose: How is it possible, on the one hand, to historicize social norms and, on the other, to uphold a normative and ideal foundation allowing for political critique? What is the systematic foundation for normative critique? How can we promote societal progress? And what practical implications might follow from this?

This paper aims to show that the answers to these questions offered by the proponents of the Marburg School diverged in a number of crucial, if not irreconcilable, respects. More specifically, I seek to identify two ways of justifying socialism within the Marburg School in light of the “scientific dispute” (Natorp 1913, 1). Cohen defended an adapted version of Kant’s moral law as a universal principle of culture that allows one to criticize capitalist norms from an ethical point of view. Rudolf Stammler (1856–1938) provided a transcendental justification of law separated from morality, arguing that the inconsistencies between the legal system and economic conditions provided the normative foundation for political criticism.

I shall argue that Cohen and Stammler approached their Kantian foundation of socialism from very different backgrounds. Although they were both inspired by Friedrich Albert Lange’s views on socialism and sought to overcome a Darwinist justification of the ‘worker’s question,’ Cohen and Stammler worked out two fundamentally different theories of Kantian socialism. Cohen’s approach was inspired by the natural law tradition, especially the version proffered by the ArIstotelian Adolf Trendelenburg. Stammler, however, considered class struggles to be the result of an ‘outdated’ legal system regulating the economic sphere, thereby providing a critical-idealist alternative inspired by Friedrich von Savigny’s ‘Historical School.’ In highlighting these differences, I suggest letting go of the descriptors ‘Marburg neo-Kantian socialism’ or ‘ethical socialism,’ which mistakenly imply a coherent foundation of socialism. Instead, I argue that these two approaches were part of a broader philosophical current in the Kantian tradition that includes various left-wing justifications of socialism beyond the Marburg School.

The paper is divided into six sections. In the second section, I highlight the fundamental differences regarding the demarcation between law and morality in Trendelenburg and Savigny. In the third section, I show that the first neo-Kantian socialist, Lange, provided an aesthetic account of natural law that grounds his historicist view on social norms. In section four, I discuss Cohen’s left-Kantian revival of the natural law tradition, which is conceptualized with Trendelenburg’s natural law and Lange’s critical idealism in mind. In the fifth section, I address Stammler’s left-Kantianism and show that he critically draws on Savigny and Lange’s historicist view. In the sixth section, I establish how Cohen and Stammler differ regarding methodology, history, and the practical implications that follow from their respective accounts, arguing that these positions are characteristic of a broader current I call ‘left-Kantianism.’ The paper concludes with a summary of the main findings and a view to potential avenues for further research.

2 Important Predecessors: Adolf Trendelenburg and Friedrich von Savigny

Three philosophical positions are hovering in the background of the ‘scientific dispute.’ The natural law theory of Adolf Trendelenburg (1802–1872), the historicist approach of the ‘Historical School’ of Friedrich von Savigny (1779–1861), and—as I will discuss in the next section—the early neo-Kantian socialism of Friedrich Albert Lange (1828–1875). Due to a lack of space, I will not discuss their theories in full. Instead, I will focus on those aspects that are later reflected in the works of Cohen and Stammler.

Trendelenburg had a major influence on natural law theory in the nineteenth century. Natural law theory in this context signifies the idea that juridical practice or legal judgments are ultimately grounded on a principle of justice that is innate to human nature or rationality. Trendelenburg was influenced by Aristotle and Kant. He offered an interpretation of the categories of time and space as being both ideal and real at the same time—a position that evoked the famous Trendelenburg-Fischer debate.^[2] In his practical philosophy, Trendelenburg defended a historically embedded view of practical rationality materialized in a “concrete” conception of the Kantian notion of universality, grounding the basis for his natural law theory (Brüllmann 2019, 207).^[3]

To understand Trendelenburg’s historically embedded concept of natural law, we first need to look at his logical and epistemological framework. In Logische Untersuchungen (1870), Trendelenburg “reforms” the logical foundation in natural philosophy (Hartung 2019, 79–83). He agrees with Hegel that rationality is a historical practice. However, he adds that Hegel’s dialectical logic fails to account for a crucial presupposition: “spatial movement” (Trendelenburg 1870, 42).

Trendelenburg illustrates the problem of “spatial movement” with the following example: “While the day is coming, it is already, and it is not yet” (1870, 38). Logically, this sentence violates the law of identity—namely that A and not-A cannot both be true at the same time. However, the problem is presented differently if we include the human being’s ability to perceive the object in its transitional mode of existence. From an Aristotle-inspired and ontological point of view, Trendelenburg argues that “contradictions” are “based on receptive intuitions,” meaning that pure thinking would rely on an intuitive category of coming-into-being (1870, 56). If we include the category of coming-into-being, we can ascribe A and not-A ontologically to an object, holding A and not-A to be true at the same time. Call this the ‘principle of continuity.’

Trendelenburg uses the principle of continuity to reformulate an account of historical reason. In his view, it is the philosopher’s task to “recognize the objects of knowledge that find their origin […] in the a priori conditions” (Trendelnburg 1870, 236). Methodologically, this requires the identification of concepts and norms that were initially generated by reason. “[A]s the spirit opens its senses, […t]he a priori principle of freedom is found in its movement [Bewegung] in physical objects and ethical norms” (Trendelnburg 1870, 237). Freedom is not only an abstract idea but finds its materialization in objects and norms constituting the facts of history. Just as the category of coming-into-being allows us to ascribe both A and not-A to the same object, so the category of coming-into-being allows us to perceive facts of history as determined and caused by a free will.

Against this background, the principle of continuity reappears in Naturrecht auf dem Grunde der Ethik (1868). Trendelenburg criticizes approaches in which an ideal principle of justice is taken as a “last foundation” (letzter Ursprung) without considering its appearance. Convinced that philosophy must “screen history regarding its [rational] origin” (1868, 5), he claims that the principle of justice “must be found in its historical formation” (1868, xi). Trendelenburg remains ‘Kantian’ as he holds onto a logical and a priori understanding of the notion of ethical freedom that guides our focus on the historical instantiations of positive laws. In this sense, he retains the distinction between the ideal and the empirical notion of morality, arguing that we must judge legal norms by their underlying focus. “In contrast to the changing particular [Besondere] of the many wills, which dresses in the majority of votes only appearing to be universal, we demand the universality [Allgemeine] as the essence of reason that underlies juridical judgments” (1868, 16). While all juridical norms are objects of experience, Trendelenburg aims to disentangle juridical laws entailing a notion of ethical universality that is distinct from norms of convention. The ‘organic worldview’—as Trendelenburg calls it—allows for a continuous view of the normative and ethical origins underlying substantive ideas in history. While in the theoretical sphere the principle of continuity builds on the category of ‘spatial movement,’ in the practical sphere the principle explains how a set of norms can be substantiated and grounded by a free rational will under the category of an ‘ethical end.’

By ethicizing the legal sphere (Hartung 2008, 297), Trendelenburg faces a novel problem. In Kant’s view, the legal and the moral realms ideally coincide. However, systematically, they target different norms. In the moral sphere, we deal with internal and autonomous laws, while in the legal sphere, we deal with external and coercive laws. But if all empirical social standards—including juridical models—are measured by an underlying ethical end, how is it possible to uphold this distinction?

Trendelenburg answers as follows: “The merit of this [Kant’s] legal concept lies in its generality [Allgemeinheit] but its defect in the generality conceived only externally” (1868/1860, 16). Since Trendelenburg considers all social norms as “ethical germs” measured by their “ethical end,” he rejects the Kantian systematic differentiation between legality and morality, where the former is based on “external means” of “coercion” (1868/1860, 12). Instead, he argues that legal norms—materialized in the social realm—are measured by their ethical end.

An entirely different view on juridical laws is painted in Vom Beruf unserer Zeit für Gesetzgebung und Rechtswissenschaft (1814) by Savigny. In contrast to the natural law tradition, Savigny rejects the idea of an innate rational principle of justice guiding our legal practices. As Reutter aptly puts it, for Savigny, “being” is “positive law” or the “concrete legal being” (2011, 75). Methodologically, Savigny argues that the legal sciences (Rechtswissenschaft) need to restrict their investigation to inductive investigations of historically formed legal contents.

Savigny’s methodology is restricted to the causal investigation of substantive norms or positive laws in their empirical appearance. What counts as ‘just’ cannot be answered on the basis of an ideal principle underlying historical judgments. Instead, justice can only be measured by the standards of the period within which such judgments emerged. While Trendelenburg argues that it is possible to recognize different sets of legal norms over time with respect to their ethical basis, Savigny criticizes such approaches for their “bottomless idleness” in assuming an ideal foundation “standing up and above” human practices (1814, 6). The legal sciences’ task is to investigate the “substantial formation” of legal systems and define the most characteristic traits of a certain period (1814, 6). In contrast to the natural law camp, which emphasizes the rational continuity in legal judgments, Savigny’s framework focuses on the contingent aspects of legal norms, saying that general claims are based on recognizing the changing character traits of different sets of legal norms over time.

Savigny does not refrain entirely from normative assertions; however, he grounds his view on a psychological theory of the Volksgeist. According to Savigny, investigating the individual character traits of legal systems means identifying the psychological principles of a society that ground the epistemic conditions of reality. This allows for inferences to be made about the stage of the “consciousness of the people” (Bewußtsein des Volkes) (1814, 9). What follows from studying historical legal textbooks is the identification of “general characterizations of a period” (1814, 9). Savigny differentiates between arbitrary moral and religious convictions, which develop “naturally” in society, and “objective” laws we intentionally institutionalize in order to regulate social behavior. Law does not evolve in a vacuum; it is the institutionalization of what we consider right (1814, 13). Savigny thus claims that the “only true and natural law is the one understood in relation and interaction to the general [political] culture” (1814, 48). Undertaking historical comparisons enables one to identify and contrast character traits of “primitive” and “higher” legal cultures. The normative principle based on which Savigny distinguishes between “primitive” and “higher” legal cultures is of a linguistic nature; the more abstract and formal the (legal) language of a culture is, the more cultivated society is.

This method is illustrated in his analysis of modern civil law. While civil law was characterized by “symbolic deeds” in earlier stages of humanity, modern civil law was marked by more “formal” language and behavior (1814, 10). Savigny claims that modern law would presuppose a level of linguistic abstraction similar to that of ancient Roman law. This example illustrates what Savigny is after methodologically: “We try to present general features of a period in which law, like language, lives in the consciousness of the people” (1814, 9). Thus, the analysis of language, focusing on the level of formality, is taken as a criterion based on which “general” statements about the cognitive stage of a “Volk”^[4] become possible (1814, 23).

Trendelenburg and Savigny both aimed to historicize knowledge, and, in this sense, they were part of a tradition reacting to ahistorical forms of idealism. Yet, their reactions to ahistorical idealism differed. Savigny’s theory does not allow for a context-free evaluation of norms. Social norms are merely depicted in their coercive, empirical, and external manner. Legal and moral norms are institutionalized (objective) reflections of a specific period. Trendelenburg seeks to identify the ethical norms underlying legal judgments, thereby holding onto a continuous and idealist view of norms by disentangling the universal element beneath empirical laws. Moreover, they were representatives of differing disciplines and generations. Savigny was 23 years Trendelenburg’s senior and—with Gustav von Hugo (1764–1844)—a founding figure of the Historical School of Jurisprudence (Historische Rechtsschule) that consisted almost exclusively of jurists. Trendelenburg, in contrast, was a philosopher and philologist who integrated historical developments into his idealist system, which was highly influential in the debates on the methodology of the history of philosophy.

3 The First Neo-Kantian Socialist: Friedrich Albert Lange

Friedrich Albert Lange—sometimes called the “father of Marburg neo-Kantianism” (Sieg 1994, 86)—was the first neo-Kantian philosopher to defend socialism. According to Lange, class struggles are an effect of evolution. Adam Smith’s sensualist account of moral sentiments, August Weismann’s adaptation of Darwinism, and Thomas Malthus’ law of population are essential reference points that, in Lange’s view, have helped to understand the capitalist ‘struggle for survival.’ However, underlying Lange’s whole philosophy is a critique of materialism and naturalism, arguing that such approaches leave the psychological and physiological conditions of (social) experience unexplored. Influenced by Hermann von Helmholtz (1821–1894) and Johannes Müller (1801–1858), Lange is convinced that materialism, broadly conceived, paves the way for a naturalist interpretation of the conditions of social experience. Understanding the conditions of social experience would mean scrutinizing the origins of egoistic behavior with the means of statistics and psychophysics (Lange 1870, 115–117). Lange did not provide an in-depth philosophical study of legal norms. However, since his view on jurisdiction remained vague, it is possible to situate him within both the natural law and the historicist traditions.

Let us first look at Lange’s account of aesthetics, which moves in a similar direction to that of the natural law tradition. Lange is convinced that we can investigate the social realm like the natural realm with empirical-scientific methods due to the subjective psychological categories of understanding. However, there is one crucial difference between the social and the natural sciences. While in the realm of nature, scientific practice is guided by a critical conception of the ‘thing-in-itself,’ the examination of the social domain presupposes an ethical ideal of “equality” (Lange 1870, 266).

Driven by the aim of overcoming old metaphysics, Lange rejects the metaphysical and logical implications of the idea of universality in Kant. Instead, he argues that the notion of universality is an aesthetic fiction. “The same principle that prevails in the realm of beauty, art, and poetry, prevails in the realm of action as the true ethical norm” (Lange 2015/1866, 554/982, emphasis added). Instead of rationalizing the concept of universality, Lange tackles the issue from a sensualist foundation and differentiates between “primitive pleasure” and “more refined sensual pleasure” (2015/1866, 509/905). The latter comprises the aesthetic joy felt when we listen to the rhythm of a song or poem, enjoy a painting’s matching colors, or imagine social norms in a coherent ethical order. By comparing the empirical social norms with the “idea of equality,” we recognize unjust social structures that conflict with our inner picture of a harmonious social order. “Only through this contrast,” claims Lange, “reality appears evil” (2015/1866, 22). In Lange’s view, we can differentiate between just and unjust norms due to our innate aesthetic inclination to create a mental picture that deviates from the given reality.

Lange’s aesthetic account is reminiscent of the natural law tradition, as it argues for an innate moral conception of justice as an ahistorical idea, which allows us to criticize social norms. To Lange, the “idea of equality” functions as a critical concept. Injustices of an unequal distribution of goods, the exploitation of workers, and the mechanisms supporting capitalism are viewed and criticized from an ethical point of view. Following this line of thought, socialism appears as a moral movement striving for legal reforms based on an aesthetic foundation of justice.

Alongside Lange’s aesthetic idealism, we find another line of argument that will later inform Stammler’s naturalist focus on class struggles. More in line with the historicist tradition, Lange bases his political philosophy, inspired by Smith, on two opposite natural dispositions underlying class struggles: our inclination for “sympathetic” behavior and our inclination for “egoistic” behavior. Class struggles appear if structures promoting egoistic behavior are in place. Here, Lange takes legality in its contingent appearance: “Between Spartans and Helots, […] between lords and subservient, between the noble and rabble existed a moral law based on class prejudices” (1866, 57). Lange builds on a relativist conception of legality, suggesting that what counts as ‘right’ depends on a legal contract that makes a legal norm just. “Even slavery or the payment of tribute to a robber can be regarded as a contract that was once considered lawful” (1870/1865, 252). His relativist conception of justice is also found in the Geschichte des Materialismus, where he states: “The whole practical philosophy is the changing and variable part of Kant’s philosophy” (Lange 2015/1866, 254/453).

To illuminate the legal causes of social strife, Lange’s account requires statistical investigation into the various tensions that occur within society. According to Lange, ‘class struggles’ indicate that a system has not accommodated the material challenges of its time, thereby deploying a legal basis promoting egoistic (instead of sympathetic) behavior. The struggle between classes would refer to “real forces” based on unsatisfied needs and desires, requiring a change of laws so that the social tensions are minimized: “If […] one complains of lack of promotion, and others regard him as a vain miser, both parts are often right in a certain sense; only the former should realize that the greater part of his reproach strikes at the social institutions existing at the time, and the latter should bear in mind that real forces are hidden behind such feelings, namely unsatisfied needs” (Lange 1870/1865, 49). Lange does not value one legal system over another based on an ideal principle. While the current system might have been a ‘good’ fit in previous times under different empirical conditions, it now causes ‘unsatisfied needs’ and is responsible for promoting egoistic behavior. Instead of moral deliberations, Lange argues here for empirical methods based on inductive reasoning to examine class struggles, allowing us to understand an unequal distribution of goods as an indication of an egoistic society. “My logic is probability calculation, my ethics are moral statistics, my psychology is based on physiology; I try in one word to move solely in the exact sciences” (Lange cited in Ellissen 1894, 106). Socialism appears as a political movement based on a sensualist notion of justice, advocating to minimize class struggles by reforming legal norms so that material needs are satisfied more evenly, and that societal norms promote social behavior.

But how do Lange’s aesthetic idealism and his sensualist materialism go together? Lange is unclear on this issue, and interpreters have put forward different interpretations. Some have argued against a systematic connection between Lange’s sociopolitical philosophy and his aesthetic Kantianism as we find it in Geschichte des Materialismus (Beiser 2014, 362; Klein 1994, 138; Vorländer 1974/1911, 122). If considered separately, then we find, in fact, two contradictory argumentative lines. However, Lange also claims that “materialism” is a stage in the course of human history moving towards a purer form of (aesthetic) idealism (2015/1866, 512/910). One could accordingly interpret the relation between Lange’s aesthetic idealism and materialistic sensualism against the background of an account that allows for methodological pluralism. In that case, the ‘idea of harmony’ appears as a ‘purer form’ of the sensualist principle of sympathy (Widmer 2022a, 2022b; Krauss 2022). Be that as it may, for our current purposes, the relation of the two lines of argumentation is less important than the fact that Lange provides interpretative allowances that place him within both respective traditions.

In his aesthetic idealism, Lange is reminiscent of the natural law tradition, arguing for an a priori idea of harmony that structures our moral perception on the basis of which norms conflicting with that order are presented to us as wrong. If we interpret Lange’s social and political philosophy without considering his (what he takes to be) ‘Kant’-inspired aesthetic idealism, political action is based on empirical statistical knowledge, informing us about the material causes of class struggles that need to be minimized.

4 Hermann Cohen’s Neo-Kantian Foundation for Ethical Socialism

In the “Introduction and Critical Appendix” to Lange’s Geschichte des Materialismus (1896), Cohen claims for the first time that “Kant was the true and real originator of German socialism” (1974/1896, 71). Cohen is convinced that if Kant’s notion of practical reason were thought through, we would conclude that democratic socialism was the only ethically justified governmental form. In this section, I argue that Cohen’s justification of socialism is informed by Trendelenburg’s logic and Lange’s critical idealism.

Before examining the parallels between Cohen and Trendelenburg and Cohen and Lange, I briefly draw attention to those aspects where Cohen differs from his predecessors. Cohen’s ethical account differs from Trendelenburg’s Aristotelianism in so far as he provides what he takes to be a ‘Platonic’ and ‘scientific’ interpretation of transcendental idealism. This implies that moral principles do not originate in perceptual content. Instead, they are considered ideal rational ‘constructions’ grounding the logic of the legal sciences (Falkenburg 2020, 132; Luft 2015, 29). Cohen’s account differs also from Lange’s.^[5] Lange takes ethics as a sub-discipline of aesthetics, thereby letting go of Kant’s categorical imperative. Cohen defends ethics as an independent field grounded by the moral law that takes historical-cultural norms (the ‘facts of culture’) as a starting point. Despite this difference, however, systematic similarities suggest that in his Kantian justification of socialism, Cohen takes inspiration from what I earlier called Trendelenburg’s principle of continuity and Lange’s ‘critical’ methodology.

Let us first look at the systematic similarities between Cohen and Trendelenburg. Together with Wilhelm Dilthey, Gottlob Frege, Franz Brentano, Heinrich Rickert, and Edmund Husserl, Cohen was one of many students of Trendelenburg (Beiser 2013, 1). In “Zur Controverse zwischen Trendelenburg und Kuno Fischer” (1871), the young Cohen commented on the Fischer-Trendelenburg debate.^[6] I will not be focusing on this debate here; instead, I shall argue that when Cohen worked out the moral law as a natural law underlying his ethical historiography, he drew on Trendelenburg’s category of ‘movement’ or ‘coming-into-being’ and renewed the principle of continuity on neo-Kantian grounds.

Cohen argues that ethical deliberation must not be viewed in isolation. Critical thinking evolves in the ‘facts of science’ and the ‘facts of culture.’ Whereas Kant’s philosophical explorations would start from a concept of experience that stands apart from scientific facts and cultural norms, Cohen embeds his transcendental method in the causal nexus of empirical reality. His ethical theory strives to detect the moral foundation in historical cultural judgments as products of reason or ‘hypotheses’—as he calls them, following Plato.^[7] Cohen broadens the meaning of Kantian ethics by arguing that we must scrutinize the “methodical unity” under which “the three cultural areas [i. e., law, religion, history] were combined to test the application of the moral law” (2001/1876, B377). Cohen’s ethical theory remains individualistic insofar as it relies on the transcendental subject. However, his conception of individual freedom is integrated “in societal and natural entanglements” (Esser 2011, 227). Embedding critical thinking in history, however, leads to a fundamental problem.

How can we disentangle the moral value of ideas in history from the causal nexus of natural and psychological components with which they are inevitably interwoven? Here Cohen finds inspiration in Trendelenburg’s concept of ‘movement’ or ‘coming-into-being’ (1981/1904, 44). In various passages, Cohen argues that the moral ideal—his novel interpretation of the ethical concept of universality—is the rational concept that vouches for continuation in history. Cohen attempts “to present Kant’s epistemological justification of ethics in the psychological movement [Bewegung] in its developments” (1981/1904, vi, emphasis added). He states: “The movement in law and state contains an immanent appeal to an external forum […]. We shall later claim the concept of history for this purpose” (1981/1904, 439). In another passage, Cohen claims: “It is history on which the idea of perpetual peace is grounded, and it vouches for the continuous movement” (1981/1904, 454). Similar to Trendelenburg’s dynamic conception of reason, Cohen supports a “dynamic” concept of reason, allowing for an ethical point of view of the ideas in the history of humanity (Luft 2015, 168).

More specifically, Cohen formulates a novel interpretation of the moral law in the second edition of Kants Begründung der Ethik. He criticizes Kant’s ethical theory for using materialistic terms that have led to a flawed depiction of the moral law. His formulation of the moral law goes as follows: “No person is allowed to be used ‘merely as a means.’ Every person must always, at the same time in the administration of the moral world, be treated as ends in themselves” (2001/1876, B279–280). Cohen takes two Kantian formulations of the moral law as comprising the individual’s fundamental right to be treated as an end in themselves in society: the formula of humanity and the formula of the kingdom of ends. Whereas Kant’s moral law asks what I ought to do, the Cohenian law asks how a moral world must be ‘administrated’ to protect human dignity, thereby adding a social and teleological aspect to the moral law (pace Furner 2019). Cohen provides an evaluative principle that allows us to identify developments stemming from a free moral will, even if the norm in question is materialized in history and thus entangled in the causal nexus. Those norms that are conceptually incoherent with the moral law must be dismissed if society is to progress.

By setting out the development of culture in its progressiveness, Cohen gives up on the systematic distinction between law and morality. Since for Cohen there is only one fundamental moral right that allows for a critical examination of normative concepts, he argues that Kant’s conception of “coercion did not grow on the ground of transcendental freedom” (2001/1876, B395). Some passages later, he claims: “Kant did not exercise that free, unbiased, sovereign criticism of positive law that gives his transcendental criticism its true life and its powerful fruitfulness” (2001/1876, B399). Like Trendelenburg, Cohen accuses Kant of mistakenly “separating law and morality,” which hindered him from seeing the potential of the moral law as a “natural law” underlying all cultural practices (2001/1876, B399). Concepts consistent with the moral law are manifestations of ethical ideas, grounding the continuation of human progress.

In Ethik des reinen Willens, Cohen adds a political component to the ideal notion of the moral law or the ‘pure will.’ The substantive prescriptive concepts constituting society change continuously; however, the state’s task has been and will always be the same, namely, to protect the dignity of its citizens. To signify the political implications, Cohen introduces the concept of ‘Allness’ (Allheit). Cohen’s conception of the moral law relies on an adaptation of Trendelenburg’s category of coming-into-being.^[8] “The state [Allheit] is the universal institution in which history represents the human race and brings it to its development” (1981/1904, 378). Trendelenburg argues that legal systems have a shared focus on an ethical end, thereby taking norms in their autonomous origin and their materialized form. Similarly, Cohen uses the methodological concept of the ideal state to disregard the causal factors on which moral ideas in history rely. The idea of the moral state functions as a “lighthouse” and an “anchor for the flood of history. It contains the last magic key for the continuation of humanity” (1981/1904, 503). The materialized rational norms differ fundamentally over time. However, the focus on an absolute end that grounds our will to systematize norms enables one to regard the history of humanity in its moral-progressive continuation. In other words, ‘Allness’ is the concept that provides continuity in the cultural domain. Like Trendelenburg, Cohen bases his practical philosophy on an ethical principle, claiming that we recognize the lasting moral value of norms under the ideal concept of the state, the ‘Allness.’

Let us now turn to the critical component in Cohen’s ethics reminiscent of Lange’s idealism. Cohen agrees with Lange that ethics must proceed critically. In contrast to the historicist camp that engages with an inductive method to examine empirical facts, Cohen’s methodology starts from historically evolved and empirically manifested legal facts—the ‘facts of culture’—and discusses their underlying ethical end. Cohen’s Kant-inspired critique of empirical concepts is well illustrated by his critique of capitalism.

Cohen criticizes the conceptual presuppositions of a capitalist legal system in which persons and objects are confused. Inheritance laws in capitalist societies are based on the misleading assumption that a “person’s will could be materialized” in an object (1981/1904, 608–609). “Capital,” on the other hand, “no longer seems to be a mere thing; it becomes a person because it acts like persons” (1981/1904, 609). Concerning the concept of labor, Cohen argues that the employer would gain, for a certain amount of time, “ownership” over the worker (ibid., 605). Thus, under capitalist law, objects are treated as persons, and laborers are reduced to their physical skills and thus treated as objects—which is incompatible with the moral law. This conceptual problem causes—to use Cohen’s words—“serious damage” (1981/1904, 607).

Cohen does not use the moral law to test maxims; instead, he critically analyzes prescriptive concepts constituting the legal framework of a capitalist society, thereby reminding us of the function of the ‘idea of harmony’ in Lange’s account. On the back of his teleological and social interpretation of the moral law (or later the ‘Allheit’), Cohen’s investigation of prescriptive notions involves, similar to Lange, a critical moment, as it allows us to identify inhumane prescriptive concepts (like capital and the idea of inheritance) that hinder society from progressing. Cohen’s interpretation of the moral law functions as a conceptual criterion against which misleading prescriptive concepts are criticized.^[9] This also grounds Cohen’s reform-based understanding of socialism: We gradually gain insights into immoral prescriptive concepts manifested in legal laws through ethical deliberation. Society progresses by bringing them in a consistent order with the moral law.

Cohen’s concept and usage of the ideal state (Allheit) comprise systematic components of Trendelenburg’s logic and Lange’s idealism. Trendelenburg’s work is reflected in Cohen’s focus on norms considered in their autonomous origin despite their heteronomous appearance. The critical component of Lange’s idealism is reflected in Cohen’s conceptual critique, illuminating wrong turns or misleading developments.

5 Historicist Tendencies in Rudolf Stammler’s Kantian Socialism

A different picture emerges in Stammler’s Wirtschaft und Recht nach der materialistischen Geschichtsauffassung (1896) and Die Lehre vom richtigen Rechte (1902). Stammler was deeply impressed by the transcendental method as Cohen had developed it in Kants Theorie der Erfahrung (1871), and, in many ways, their views align. Stammler agrees with a critical interpretation of Kantian philosophy that grounds the logic of cognition on an a priori idea of systematicity. In the same vein, he follows Cohen’s rejection of psychological approaches. In Rechts- und Staatstheorien der Neuzeit (1925), Stammler explicitly criticizes the concept of Volksgeist as it “mistakes the mind for a psychic phenomenon” (1925, 50–51). Like Cohen, Stammler rejects purely psychological approaches for their unscientific foundation and argues that the legal sciences should deal with the transcendental logic of legal judgments. However, as I will show in this section, Stammler’s position differs from Cohen’s account in two crucial respects: he rejects Cohen’s proposal of an ethical foundation of law and argues for the need to include inductive research on the historical and empirical conditions of a society.

Stammler differentiates between the ‘formal’ or ‘legal’ and the ‘material’ or ‘economic’ side of sociality. On a formal level, Stammler excludes ethics from the legal sphere. In a letter from 1892 to Stammler, Natorp suggests reading Cohen’s classification of the cultural sciences in Kants Begründung der Ethik (KBE) (Stammler 1896 [1892], 213). In his response, Stammler writes: “Having reread [Cohen’s] justification of ethics [in KBE], I see now clearly that moral laws cannot exist in our experience at all” (1896 [1892], 213). The moral law—taken as the formal principle governing the internal state of the moral agent—could never “come into congruence” with the social norms that are “empirically conditioned” (1896 [1892], 213). According to Stammler, Kant rightfully differentiated between the a priori conditions of legal judgments, dealing with heteronomous and external laws regulating the social sphere, and the a priori conditions of moral judgments, which deal with internal laws. His understanding of legality, however, also differs fundamentally from the Kantian natural law that draws on an account of external freedom. Stammler’s Wirtschaft und Recht (1896) grounds an epistemic ‘natural law,’ which goes as follows:

By natural law, I understand legal propositions which contain the theoretically correct law under empirically conditioned circumstances; which do not yet have positive force merely because of this insight but function as a source of law demanding a change or reorganization of the law in force. (Stammler 1896, 185, emphasis added)

Stammler’s ‘theoretically correct law’ is not based on a practical account of freedom that sets the foundation for normative statements. Instead, the ‘theoretically correct law’ is a scientific ideal that grounds the telos of both the natural and legal sciences.

Stammler argues that there is only one type of cognition (Erkenntnisart), theoretical reason, that grounds the foundation of law. Stammler’s ‘theoretically correct law’ presupposes free agents capable of setting rules for themselves. However, instead of providing an account of legality that deduces a system of rights from a positive account of freedom (as we find in Cohen and Kant), Stammler takes legal norms in their substantive and changing nature as they appear in the sphere of causality. This does not mean that Stammler gives up on a neo-Kantian foundation of law. However, he objects to Cohen’s claim that there are two types of cognition— theoretical and normative cognition—and argues that, as in the natural sciences, we should pursue a systematic formulation of laws that grounds a just regulation of the empirical (economic) conditions:

The regular repetitions of certain phenomena, united to the respective unity, are called laws. And all individual laws are only possible by the fact that a generally valid lawfulness of nature lies at the basis without which every single law of nature in itself would be completely groundless and without the provable value of knowledge. (Stammler 1896, 350)

Stammler formulates the ‘theoretically correct law’ as a principle that follows from the same account of systematicity as the natural realm.

While Cohen opts for deductive judgments and focuses on ideas and their (un)ethical instantiation in society, Stammler’s deductions are based on empirical facts that need to be obtained with empirical methods. The underlying idea is the following. While the economy follows its own rules, it is our task to observe economic relations and bring the “blind forces” under control (1896, 29). According to Stammler, economic conditions constitute social conditions. However, it is possible to intervene in such naturally evolved economic processes by regulating the market. Stammler illustrates this with the following analogy: “If a mountain stream runs the risk of flooding the lowlands, we calculate and construct streambeds to contain and control the flow” (1896, 50). Social nature, too, demands regulations; the legal system has the power to regulate and fix misguided developments by steering them in the right direction (1896, 51–52).

What follows from the ‘theoretically correct law’ under ‘empirical conditions’ is an account of social progress that requires two methodologies: (i) an examination of empirical facts requiring inductive reasoning; and (ii) rendering the acquired facts deductively under the idea of a more unified or balanced picture of society. “[N]ot the exact collection of isolated data is what makes a good historian, but rather the right synthesis of the universal concept of law” (1896, 23). Once we realize that “under this economic foundation […] there still hovers the old legal order of times long past” (1896, 47), we have the epistemic means to overcome the social tensions expressed in class struggles. In this vein, Stammler emphasizes that, technically speaking, it would be wrong to call the capitalist system “unjust”; instead, it would be more apt to call it “economically outdated” (1896, 47–48). Progress is the “human attempt” to “regulate and guide the otherwise wild and unbridled forces of social production” (1896, 30).

The reason why Stammler thought of the ‘theoretically correct law’ as a principle free from a normative conception of justice remains unclear.^[10] More importantly, Stammler’s engagement with the empirical material that combines inductive examinations of class struggles and a deductive rendering of empirical facts under the idea of systematicity reflects his educational background in the Historicist School of Savigny. Cultural progress does not involve the contemplation of a practical law, guiding the morally right path. Instead, the progress of legal systems is measured by a theoretical principle and informed by empirical circumstances. Stammler reads Lange against this background when characterizing him as a theorist of ‘social materialism.’ Following the empiricist line of argument in Lange, he claims: “The lawfulness of the social life of people is, according to the doctrine of social materialism, a regularity of economic phenomena” (1896, 29).^[11] For a successful rendering of empirical facts that inform our political action, we need to conduct inductive examinations of the “economic phenomena” constituting a society, which allows us to gain insights into the origins of class struggles (1896, 29).

Stammler’s epistemological principle of the ‘theoretically correct law’ grounds a principle of cultural progress according to which bringing empirical forces into systematic order leads to a more balanced satisfaction of needs. Reminiscent of Savigny and Lange, then, Stammler’s account focuses on the origins of class struggles in order to gain information on how to reform the legal system.

6 The ‘Scientific Dispute’ and ‘Left-Kantianism’

The ‘scientific dispute,’ to use Natorp’s term, started in the early 1890s. Stammler was from the outset frustrated by Cohen’s attempt to ground all social norms on an ethical foundation without acknowledging their a priori systematic differences.^[12] In this section, I highlight the main divergences between Cohen and Stammler. I argue that their disagreement is characteristic of a more general intellectual atmosphere of the pre-war era when philosophers were seeking a justification for socialism on Kantian grounds.

First, their views on the demarcation between law and morality fundamentally differ because of their different outlooks on what the critical method is supposed to achieve. Cohen is inspired by Trendelenburg’s category of coming-into-being and Lange’s critical use of the idea of harmony, which allows identifying conceptual inconsistencies with the moral law or ‘Allheit.’ Cohen does not simply forget to include the coercive and heteronomous characteristics of positive laws and he does not deny the power given to institutionalized rules. He rejects a systematic separation of law and morality because accepting a foundation that allows for coercive and heteronomous laws would undermine the critical aspect of his methodology that identifies conceptual inconsistencies. Thus, for methodological reasons, Cohen denies the Kantian distinction between the internal, ethical, autonomous, and subjective domain of morality on one side and the external, legal, and coercive realm on the other.

Stammler adopts a different view of what the critical method is meant to achieve. It is not the task of philosophy to identify ethical inconsistencies; its task is instead to engage with empirical facts provided by the empirical sciences in order to understand the origins of class struggles that lead to an uneven satisfaction of needs. The a priori conditions of legality do not include a natural law based on a practical account of justice. His conception of the ‘theoretically correct law’ is meant as an epistemological principle that grounds social progress. Thus, Stammler, too, has a methodological reason to reject the Cohenian idea of a universal moral principle underlying his critique of the capitalist legal system because it would undermine the fact that legal contents are continuously changing.

Second, their varying conceptions of legality trace back to different methodological approach for dealing with ‘facts.’ Cohen historicizes reason to show that some social norms are based on ethical judgments, even though they are interwoven with causal factors. This provides the critical foundation upon which societal developments are evaluated.^[13] Cohen’s critique engages with ideas materialized in the legal foundation constituting society. However, his methodology is based on deductive reasoning. Stammler’s methodology, on the other hand, is based on deductive reasoning, and yet asks additionally for inductive investigations of the social reality (i.e, statistical knowledge). While Cohen sees contradictions as based on ethical deliberation, Stammler takes the inconsistencies between law and economy as empirically measurable phenomena, materialized in the social class struggles. Stammler’s account is shaped by the requirement to obtain empirical knowledge with the methods of the empirical sciences; Cohen’s historical facts of culture are taken as a given.

Third, based on their different methodologies, Cohen and Stammler criticize capitalism on different levels. Cohen’s ethical critique is based on a concept of change that requires action from the bottom up. His methodology is meant to critique singular developments instead of a whole economic system—an idea illustrated in his affirmative attitude towards workers’ unions (Genossenschaften). Stammler’s socialism, however, includes a top-down approach as it is meant to investigate economic systems and the ‘suitedness’ of the corresponding legal system. In more modern terms, one could say that Cohen’s socialism has more liberal tendencies, arguing for the individual right always to be treated as an end in oneself. Meanwhile, Stammler’s socialism seeks to change the economic flow on a systematic level, thereby moving to an economic system that is centrally organized and one that gives more power to the state. Although on a practical level, these approaches are not mutually exclusive, their underlying method with which they come to these conclusions is different: Cohen’s socialism is based on the deliberation about laws that protect the individual’s fundamental right to a dignified life. Stammler’s conception of socialism is meant to correct the laws that create empirically measurable societal problems and injustices.

Their differences show that Marburg neo-Kantian socialism was not a coherent current, seeking an ethical justification for socialism. Admittedly, there is reason to regard them as part of the same philosophical school considering their critical-idealist take on Kant and their reaction to a form of idealism that did not engage sufficiently with the empirical aspects of society. However, like Trendelenburg and Savigny, they differed in age and disciplinary background, and thus their philosophies diverged fundamentally regarding the conception of law, history, and their view of what the critical method was meant to achieve. Their theories belonged, consequently, to two distinct camps: an ethical and epistemic justification of socialism. Thus, it is misleading to speak of a coherent school of thought.

Another reason to break with current characterizations is that Cohen and Stammler were not the only ones to offer left-wing interpretations of Kantian socialism at the time. Up until the First World War, a wide variety of original left-wing interpretations of the Kantian system emerged in the German-speaking world. Austro-Marxists like Otto Bauer (1881–1938) and Max Adler (1873–1937) sought to combine Marxism with Kantian thought. Although their approaches might have been influenced by the Marburg School, their positions were distinct in crucial respects. Adler, for example, criticized Cohen for refraining from the materialist elements of Kant’s philosophy of history. In his view, the materialist elements in Kant’s works provided the most valuable foundation for combining Kant with Marx. In “Idee zu einer allgemeinen Geschichte in weltbürgerlicher Absicht” (1784/1959), Kant argues that historical progress is based on human social nature characterized by the tendencies to socialize and isolate. Here sociality is understood in a natural rather than an ethical sense, claiming that we have learned over time that we can reach our goals more efficiently by working together. This “social-psychological” conception of human progress provides, according to Adler, valuable insights that would “complement Marx’s conception of dialectical materialism” (Adler 1904/1976, 167).

Other Kant-inspired socialist theories were developed by Conrad Schmidt (1863–1932) and Ludwig Woltmann (1871–1907). Schmidt rebuked Cohen for his Kantian-ethical justification of socialism. For Schmidt, Cohen’s philosophy was built on a “rigid dogmatism of the moral system derived from pure reason,” which would virtually “rape” the concept of ethical consciousness taken in a causal and heterogeneous manner (Schmidt 1974/1900, 105). Despite his rejection of Kant’s practical reason, Schmidt argued that Marxism needed to be reformulated based on Kant’s theoretical philosophy. Woltmann, by contrast, agreed with Cohen’s ethical justification of socialism. However, he criticized Cohen’s critical-idealist approach to Kant, arguing instead for a metaphysical reading of Kant’s moral philosophy, which he considered the “orthodox” reading (Woltmann 1974/1900, 117–118).

Even Natorp, Karl Vorländer (1860–1928), and Franz Staudinger (1849–1921), who drew on a Cohenian account of socialism in their own work, identified fundamental problems in Cohen’s position. Vorländer criticized Cohen for not sufficiently differentiating between his own claims and Kant’s (Vorländer 1974/1911, 286). Staudinger was critical of Cohen’s theoretical philosophy (Staudinger 1986/1902, 292) but aligned with Cohen’s ethics. However, he developed it further into a cultural theory of social layers he called “social cells” (Staudinger 1914, 145).

The Marburg School was not a coherent movement, either philosophically or politically. The question of how far other left-Kantian approaches align with the natural law and the historicist camps is a question for further research. The crucial point is that Cohen and Stammler were part of a broader philosophical current that was striving to provide a Kantian alternative to Marxist socialism that is neither defined by an ethical theory nor tied to Marburg.^[14]

7 Summary and Outlook

In this paper, I have argued against current views suggesting either that Marburg neo-Kantian socialism was a coherent ‘school,’ or that all Kantian approaches developed in the decade prior to the First World War were based on an ethical foundation. I have focused on the ‘scientific dispute’—as Natorp described it in 1913—between two theories within the Marburg School: Hermann Cohen’s ethical and Rudolf Stammler’s historicist justification of socialism, and explained their theories by tracing their origins.

By shedding light on these different Kantian theories of law, history, and politics, I have argued that it is better to give up the term ‘Marburg neo-Kantian socialism,’ which gives the misleading impression of a cohesive school of thought. To signify the variety of left-wing political interpretations of Kant right before the outbreak of the First World War, I have suggested that we subsume these positions under the umbrella term ‘left-Kantianism.’

Left-Kantianism at the turn of the twentieth century remains an underexplored topic. With this paper, I have endeavored to establish the importance of reconsidering classifications that conceal the variety of positions within a movement that was dissatisfied with the philosophical implications of Marxism and so sought a Kantian justification of socialism. My choice of terminology—‘left-Kantianism’—is deliberately open since further research is required on individual thinkers before a clear and adequate definition of this philosophical current can be provided. This paper has attempted to make a first step towards that end. I hope that others will follow my lead.