In continuing my expositions regarding Schopenhauer’s critique of Kant I now turn to Schopenhauer’s reading of, and terse polemic against, Kant’s ambivalent concept of the “ding an sich”, or “thing[s]” in itself.

If Schopenhauer’s understanding of this gnomic Kantian concept is correct – and this is by no means indubitably the case – then his argument against the concept is terminal to its verity. I will explain Schopenhauer’s critique below and attempt to present some insightful readings and quotations from Kant and his interpreters as to whether or not Schopenhauer’s criticisms are sound, and if not, why his reading of Kant bastardizes the Konigsbergian’s formulation.

For Kant, all appearances and phenomena known are conditioned and understood in terms of the knower’s “categorical” and “form[al]” impositions on it. That is to say, as objects to subjects, the former are necessarily processed and transcendentally interpreted by the faculties of the latter. Kant therefore opposes the thing in itself to appearances, as that which exists perspectiveless outside of the active sensibility of the subject. It is that “other” which is not known but which stands in a hitherto noted “ambivalent” relationship to the objects of one’s perceptions and knowledge. The nature of that relationship is what is at stake in the diverse interpretations and criticisms of Kant’s “ding an sich”, but let us start with Schopenhauer’s interpretation and resulting critique.

Kant’s failing, according to Schopenhauer, is a result of the same overall problem for which he lampoons Kant’s theory of the “understanding” and perception, namely that Kant “…did not properly separate knowledge of perception from abstract knowledge.” Schopenhauer believes that Kant tries to present things in themselves as sine qua nons of the experience of phenomena without being able to consistently relate the perceptual to the noumenal (the thing in itself as the object of thought). Kant uses relations of a subjective or categorical nature, specifically causality, to relate these noumena – the role of which is purportedly non-subjective – to experience. If the thing in itself is what lies behind or outside of the relations of subject to object (or the relationship of the known to the knower) and is the ultimate ground of things as such, then the transcendental (and hence subjective) category of cause and effect is not to be applied to the thing in itself. Speaking of the “ding an sich” in terms of its causal relation to appearances would dethrone any concept of the “ding an sich” from its role as an ultimate role in grounding subject-object interactions and relegate it to the category of the subjective. Kant’s greatest contribution, according to Schopenhauer, is noting that reason and understanding can only apply intelligibly to what is sensed, perceived, and cognitions that abstract from these (precisely because the “transcendental” forms that allow reason and understanding present the subject with its intuitions of the world, precluding the intelligibility of that which lies outside of that which is experienced and the forms by which experience occurs). In order to successfully establish a relationship between things in themselves and appearances, the relationship cannot be causal and still be consistent with the underlying assumptions that allow this dichotomy to be made in the first place[1]. In fact, there cannot be a “relationship” in any sense that relies on subjective understanding at all, and this leads Schopenhauer to his altogether different approach to the “ding an sich”: a dual-aspect theory which identifies noumena and phenomena as two sides of the same coin, but this theory is the cornerstone of Schopenhauerian metaphysics and is far too extensive and intricate to outline here.

Schopenhauer sees his critique of Kant’s thing in itself as definitive and cut-and-dried: the following quote is a large portion of the attention that he gives this issue in the Appendix to the World as Will and Representation.

“Kant bases the assumption of the thing-in-itself, although concealed under many different turns of expression, on a conclusion according to the law of causality, namely that empirical perception, or more correctly sensation in our organs of sense from which it proceeds, must have an external cause. Now, according to his own correct discovery, the law of causality is known to us a priori, and consequently is a function of our intellect, and so is of subjective origin. Moreover, sensation itself, to which we here apply the law of causality, is undeniably subjective; and finally, even space, in which, by means of this application, we place the cause of the sensation as object, is a form of our intellect given a priori, and is consequently subjective. Therefore the whole of empirical perception remains throughout on a subjective foundation, as a mere occurrence in us, and nothing entirely different from and independent of it can be brought in as thing-in-itself, or show to be a necessary assumption. Empirical perception actually is and remains our mere representation; it is the world as representation.” (436)

In favor of Schopenhauer, though Kant continuously affirms that the “the transcendental object remains unknown to us” (85) in his Transcendetal Aesthetic, and that “What objects may be in themselves, and apart from all this receptivity of our sensibility, remains completely unknown to us” (82), he nevertheless predicates these transcendental objects in terms of subjective and sensible terms when he writes in the Prolegomena that “things as objects of our senses existing outside us are given, but we know nothing of what they may be in themselves, knowing only their appearances, i.e., the representations which they cause in us by affecting our senses…”[2] (30). thereby violating his concluding thought in his seminal Transcendental Aesthetic: “judgments… can never extend beyond the objects of the senses; they are valid only for objects of possible experience.”

Yet, I think that this “causal” formulation is uncharacteristic of Kant, even if he occasionally slipped into using this sort of language. Other sections of the Prolegomena suggest a very different conception of the “ding an sich” from the one that Schopenhauer so effortlessly rebuts. At risk of overstepping the bounds of this essay, it is worth noting that Kant does not tend to affirm the sort of “two-world” ontological theory of the thing-in-itself that the “causal” relationship interpretation assumes. In fact, I would argue that one good interpretation of Kant’s “thing in itself” is as a psychological “leftover” which the faculty of reason establishes to ground “appearances” with an antithetical concept that is subjectively necessary (e.g. p.53).

…[in] things in themselves, reason finds that completion and satisfaction, which it can never hope for in the derivation of appearances from their homogeneous grounds, and because these actually have reference to something distinct from them (and totally heterogeneous), as appearances always presuppose an object in itself and therefore suggest its existence whether we can know more of it or not. (89)

Here Kant says that the object in itself’s existence is “suggested” by the faculty of reason, a faculty which tells the subject nothing of the objective world, but which is responsible for ideas and abstract judgments. Its “suggestion” by this faculty really only testifies to the make-up of this subjective faculty: that reason finds its “completion and satisfaction” in this concept could mean that the thing in itself is merely a fantastic projection of the faculty of reason: a ground for appearances that thinking will find necessary, to say nothing of in what sense, if any, the “ding an sich” is “real” – or what this could possibly mean within Kant’s framework. Kant writes a bit later on: “The world of sense contains merely appearances, which are not things in themselves; but the understanding must assume these latter ones, viz. noumena” (94). Here Kant uses the language of “assumption” and necessity that points the reader in direction of the human “understanding” as responsible for “things in themselves.” It seems likely in light of all of the more charitable (and perhaps rigorous) interpretations of Kant – e.g. Henry Allison –, that Schopenhauer’s critique is an attack on a strawman. Kant clearly states that the thing in itself is the “objective boundary” of experience and its “highest ground” (95). In and of themselves, these characterizations point to an interpretation of the “ding an sich” that should differ from Schopenhauer’s: the role of things in themselves is not merely causal, but has to do with grounding appearances and knowledge/judgment itself[3].

Whether or not Schopenhauer’s critique of Kant on this subject is sound depends upon whether or not one agrees with Schopenhauer’s interpretation and reading of Kant. If the best understanding of Kant’s things-in-themselves is not causal, then much sophisticated interpretation of the concept is required to successfully account for all of the diverse ways in which the concept is spoken about and used in Kant’s works. If, however, Schopenhauer’s reading of Kant is correct then the polemic follows in turn to devastating effect.

[1] Comparable critiques of Kant’s conception of the “ding an sich” are offered by Maimon and Jacobi.

[2] Also: “For sensuous perception represents things not at all as they are, but only the mode in which they affect our senses…” (31)

[3] Notably, the interpretation I proposed for the purposes of this essay would bring Kant dangerously close to a more Berkeleyian absolute idealism, something that he strove to avoid and distinguish himself from: so much so that after Kant’s first edition of the Critique had been widely read as Berkeleyian, Kant made some changes to the second edition to differentiate his philosophy from the Bishop’s. Schopenhauer traces the “causal” re-formulation of the “ding an sich” to this point and himself points out that Kant’s shift away from stronger idealism to his second edition of the Critique made the concept of the “ding an sich” incoherent. Whether or not Kant was able to have his cake and eat it too, that is to say, whether he could manage to avoid absolute idealism without having to postulate a mistaken concept of things-in-themselves remains for Kant scholars and interpreters to debate.