Neo-Kantianism

2. The debate about the Transcendental Aesthetic

While the back to Kant movement called for a return to Kant to reconcile philosophy with the sciences, it seemed necessary to reconsider some parts of Kant’s doctrine of the elements of knowledge, in particular the Transcendental Aesthetics. Herbart (1825) called into question Kant’s argument for the aprioricity of space, pointing out that the necessity of the representation of space does not follow from the impossibility of abstracting from it in the cognition of extended objects. Herbart believed that this cognition cannot be understood in terms other than those of a psychological process leading to a subjective representation. This led to a discussion about whether Kant’s a priori forms are only valid for appearances, as Kant claimed, or whether they also apply to things in themselves. Trendelenburg (1840) answered the latter question affirmatively, arguing that Kant had failed to consider the possibility that space and time are both subjective and objective, insofar as they are derived from movement. Trendelenburg ruled out the view that space and time are objective, because there is also a kind of movement that consists in ideal operations with mathematical points. The subjective/objective view follows from the fact that such a movement corresponds to a possible realization in physics.

In 1865–70, there arose a controversy between Trendelenburg and Kuno Fischer about the correct interpretation of Kant’s Transcendental Aesthetics, but also about open issues including the source of justification for a priori cognitions, the status of mathematical judgements, the applicability of mathematics to empirical reality. It was in connection with this discussion that Cohen developed his seminal interpretation of Kant (Cohen 1871a; 1871b. See also Natorp 1912b; Cassirer 1912, 1918). Cohen sided with Trendelenburg in holding the subjective/objective status of Kant’s forms of sensibility. At the same time, Cohen emphasized that the objective value of a priori cognition is a direct consequence of Kant’s Copernican revolution: the objects of knowledge must conform to the a priori forms of the mind, and the idea of an absolute object affecting our sensibility lies outside the possibility of experience. Cohen pointed out, however, that the Kantian conception of experience as something constructed emerged only gradually in the Prolegomena and in the additions to the second edition of the Critique of Pure Reason, where Kant introduced the transcendental investigation of the possibility that nonempirical representations apply to the objects of experience a priori. Accordingly, Cohen distinguished the ‘transcendental’ meaning of a priori cognition as necessary for the possibility of experience from the ‘metaphysical’ meaning of it as universal and necessary cognition prior to sensory experience (Cohen 1871a: 35–6). Cohen’s strategy to defend the Kantian theory of space was to point out that the new insights into the psychological origin of the representation of space may have shaken the metaphysical meaning of the a priori, but not the fact that an ideal structure of space is presupposed for the localization of extended objects.

Cohen first presented his interpretation in Kants Theorie der Erfahrung [Kant’s Theory of Experience] (1871), which was followed by Kants Begründung der Ethik [Kant’s Foundation of Ethics] (1877) and Kants Begründung der Ästhetik [Kant’s Foundation of Aesthetics] (1889). These works together offer a reading of Kant’s critical philosophy as a comprehensive theory of experience articulated into a priori forms that manifest themselves in science, as well as in juridical and social institutions. Cohen’s emphasis on the need for the transcendental cognition to rely on the fact of science allowed him to mark a distinction with all kinds of psychological processes. This ruled out the physiological reading of the Kantian a priori proposed by Helmholtz and the other protagonists of the back to Kant movement, but also opened the door to a functionalization of the conditions of knowledge that goes beyond the empirical psychology of Kant’s time. As Cohen especially emphasized in the revised edition of Kants Theorie der Erfahrung (1885), these conditions provide a construction of experience only when they are considered as an interconnected whole. While much of the debate had focused on the forms of sensibility, Cohen drew attention to the more fundamental role of the synthetic principles that enable the application of the categories of the understanding to the empirical manifold. This allowed him to shift the focus from the question concerning the cause of sensations to the problem of movement as an object of the mathematical science of nature. In this way, Cohen picked up another theme originally derived from Trendelenburg. At the same time, Cohen’s reading of Kant lent plausibility to a different interpretation of the thing in itself as a ‘limiting concept’. Such a concept is needed in order to restrict the possibility of knowledge to the realm of contingent experience, but it also plays a regulative role in the extension of scientific explanations towards the idea of a comprehensive system of nature.

Cohen’s defence of the Kantian theory of space was taken up by Alois Riehl in another influential work for the renewal of critical philosophy (Riehl 1876; 1879; 1887). Riehl sought to take into account Helmholtz’s empirical explanation of the origins of spatial intuitions and basic geometrical notions, as well as the issue of determining the hypotheses concerning physical space after the discovery of non-Euclidean geometries. Riehl’s strategy to avoid a contradiction with the Kantian theory of the a priori forms of intuitions was to point out that only these forms express the laws of our cognition, whereas the empiricist theories may be correct in showing the role of the empirical material in the development of particular intuitions from the various physiological spaces (Riehl 1879: 279). Riehl’s argument led him to emphasize the empiricist themes of critical philosophy and to defend a realist conception of the thing in itself that was opposed to Cohen’s. Riehl’s interpretation of critical philosophy was highly valued in South West German neo-Kantianism, and remained an important reference for the next generation of neo-Kantians dealing with the problem of space (Bauch 1907; Hönigswald 1909; 1912).