Critique of the Kantian Philosophy (German: "Kritik der Kantischen Philosophie") is a 143-page essay which Arthur Schopenhauer appended to the first volume of his The World as Will and Representation (1818). He wanted to show Immanuel Kant's errors so that Kant's merits would be appreciated and his achievements furthered.
At the time he wrote his criticism, Schopenhauer was acquainted only with the second (1787) edition of Kant's Critique of Pure Reason. When he later read the first (1781) edition, he said that many of the contradictions he had identified in the second edition had been absent from the first edition.
Kant's merits According to Schopenhauer's essay, Kant's three main merits are as follows: The distinction of the phenomenon from the thing-in-itself (Ding an sich) The intellect mediates between things and knowledge Locke's primary qualities result from the mind's activity, just as his secondary qualities result from receptivity at any of the five senses A priori knowledge is separate from a posteriori knowledge The ideal and the real are diverse from each other Transcendental philosophy goes beyond dogmatic philosophy's "eternal truths", such as the principle of contradiction and the principle of sufficient reason. It shows that those "truths" are based on necessary forms of thought that exist in the mind. The explanation of how the moral significance of human conduct is different from the laws that are concerned with phenomena The significance is directly related to the thing-in-itself, the innermost nature of the world Religious scholastic philosophy is completely overthrown by the demonstration of the impossibility of proofs for speculative theology and also for rational psychology, or reasoned study of the soul
Schopenhauer also said that Kant's discussion, on pages A534 to A550, of the contrast between empirical and intelligible characters is one of Kant's most profound ideas. Schopenhauer asserted that it is among the most admirable things ever said by a human. The empirical character of a phenomenon is completely determined The intelligible character of a phenomenon is free. It is the thing-in-itself which is experienced as a phenomenon.
Kant's faults
Fundamental error
Perceptions and concepts Kant wanted to make the table of judgments the key to all knowledge. In so doing, he was concerned with making a system and did not think of defining terms such as perception and conception, as well as reason, understanding, subject, object, and others.
Fundamental error: Kant did not distinguish between the concrete, intuitive, perceptual knowledge of objects and the abstract, discursive, conceptual, knowledge of thoughts. Kant began his investigation into knowledge of perceived objects by considering indirect, reflective knowledge of concepts instead of direct, intuitive knowledge of perceptions. For Kant, there is absolutely no knowledge of an object unless there is thought which employs abstract concepts. For him, perception is not knowledge because it is not thought. In general, Kant claimed that perception is mere sensation. In accordance with Kant's claim, non-human animals would not be able to know objects. Animals would only know impressions on their sense organs, which Kant mistakenly called perception. Kant had erroneously asserted that full, perceived objects, not mere sensations, were given to the mind by the sense organs. Perception, however, according to Schopenhauer, is intellectual and is a product of the Understanding. Perception of an object does not result from the mere data of the senses. It requires the Understanding. Therefore, if animals do not have Understanding, in accordance with Kant, then they have only Sensation, which, Schopenhauer claimed, gives only raw sense data, not perceived objects. Schopenhauer considered the following sentences on page A253 of the Critique of Pure Reason to encapsulate all of Kant's errors: If all thought (by means of categories) is taken away from empirical knowledge, no knowledge of any object remains, because nothing can be thought by mere intuition or perception. The simple fact that there is within me an affection of my sensibility, establishes in no way any relation of such a representation to any object. On page A253, Kant stated that no knowledge of any object would remain if all thought by means of categories were removed from empirical knowledge. Schopenhauer claimed that perception occurs without conceptual thought. On page A253, Kant stated that a concept without an intuition is not empty. It still has the form of thought. Schopenhauer claimed that perceived representations are the content of a concept. Without them, the concept is empty.
Secondary errors
Transcendental analytic Kant asserted that metaphysics is knowledge a priori, or before experience. As a result, he concluded that the source of metaphysics cannot be inner or outer experience. Schopenhauer claimed that metaphysics must understand inner and outer experience in order to know the world and not empty forms. Kant did not prove that the material for knowing the world is outside of the experience of the world and merely in the forms of knowledge. Kant's writing was obscure. Kant took the Greek word noumena, which meant "that which is thought," and used it to mean "things-in-themselves." (See Sextus Empiricus, Outlines of Pyrrhonism, Book I, Chapter 13: "Anaxagoras opposed what is thought (noumena) to what appears or is perceived (phenomena).") Kant tried to create a logical, overly-symmetrical system without reflecting on its contents. He didn't clearly explain the meaning of and relationships between represented objects, representing subjects, existence, truth, illusion, error, sensations, judgments, words, concepts, perceptions, understanding, and reason.
Concepts Kant didn't clearly explain concepts in general: Concepts of the understanding (common concepts and categories). Concepts of Reason (Ideas of God, Freedom, and Immortality). He divided reason into theoretical and practical, making practical reason the source of virtuous conduct. Idealism Kant altered his first edition to: suppress the idealistic assertion that objects are conditioned by the knowing subject;
Object-in-itself and thing-in-itself According to Schopenhauer, there is a difference between an object-in-itself and a thing-in-itself. There is no object-in-itself. An object is always an object for a subject. An object is really a representation of an object. On the other hand, a thing-in-itself, for Kant, is completely unknown. It cannot be spoken of at all without employing categories (pure concepts of the understanding). A thing-in-itself is that which appears to an observer when the observer experiences a representation.
Kant altered his first edition to: claim that the spatially external thing-in-itself causes sensations in the sense organs of the knowing subject. Kant tried to explain how: a perceived object, not mere raw sensation, is given to the mind by sensibility (sensation, space, and time), and how the human understanding produces an experienced object by thinking twelve categories. Kant doesn't explain how something external causes sensation in a sense organ. He didn't explain whether the object of experience (the object of knowledge which is the result of the application of the categories) is a perceptual representation or an abstract concept. He mixed up the perceptible and the abstract so that an absurd hybrid of the two resulted. There is a contradiction between the object experienced by the senses and the object experienced by the understanding. Kant claims that representation of an object occurs both through reception of one or more of the five senses, and through the activity of the understanding's twelve categories. Sensation and understanding are separate and distinct abilities. Yet, for Kant, an object is known through each of them. This contradiction is the source of the obscurity of the Transcendental Logic. Kant's incorrect triple distinction: Representation (given to one or more of the 5 senses, and to the sensibilities of space and time) Object that is represented (thought through the 12 categories) Thing-in-itself (cannot be known). Schopenhauer claimed that Kant's represented object is false. The true distinction is only between the representation and the thing-in-itself. For Schopenhauer, the law of causality, which relates only to the representation and not to the thing-in-itself, is the real and only form of the understanding. The other 11 categories are therefore unnecessary because there is no represented object to be thought through them. Kant sometimes spoke of the thing-in-itself as though it was an object that caused changes in a subject's senses. Schopenhauer affirmed that the thing-in-itself was totally different from phenomena and therefore had nothing to do with causality or being an object for a subject. Excessive fondness for symmetry: Origin of Kant's Transcendental Logic: As pure intuitions (in the Transcendental Aesthetic) were the basis of empirical intuitions, pure concepts (in the Transcendental Logic) were made the basis of empirical concepts. As the Transcendental Aesthetic was the a priori basis of mathematics, the Transcendental Logic was made the a priori basis of logic. After discovering empirical perception is based on two forms of a priori perception (space and time), Kant tried to demonstrate that empirical knowledge is based on an analogous a priori knowledge (categories).
Schemata He went too far when he claimed that the schemata of the pure concepts of the understanding (the categories) are analogous to a schema of empirically acquired concepts. A schema of empirical perception is a sketchy, imagined perception. Thus, a schema is the mere imagined form or outline, so to speak, of a real perception. It is related to an empirical abstract concept to show that the concept is not mere word-play but has indeed been based on real perceptions. These perceptions are the actual, material content of the empirical abstract concept. A schema of pure concepts is supposed to be a pure perception. There is supposed to be a schema for each of the pure concepts (categories). Kant overlooked the fact that these pure concepts, being pure, have no perceptual content. They gain this content from empirical perception. Kant's schemata of pure concepts are entirely undemonstrable and are a merely arbitrary assumption. This demonstrates Kant's purposeful intention to find a pure, a priori analogical basis for every empirical, a posteriori mental activity.
Judgments/categories Derived all philosophical knowledge from the table of judgments. Made the table of categories the basis for every assertion about the physical and the metaphysical. Derived pure concepts of the understanding (categories) from reason. But the Transcendental Analytic was supposed to reference only the sensibility of the sense organs and also the mind's way of understanding objects. It was not supposed to be concerned with reason. Categories of quantity were based on judgments of quantity. But these judgments relate to reason, not understanding. They involve logical inclusion or exclusion of concepts with each other, as follows: Universal judgment: All A are x; Particular judgment: Some A are x; Singular judgment: This one A is x. Note: The word "quantity" was poorly chosen to designate mutual relations between abstract concepts. Categories of quality were based on judgments of quality. But these judgments also are related only to reason, not to understanding. Affirmation and denial are relations between concepts in a verbal judgment. They have nothing to do with perceptual reality for the understanding. Kant also included infinite judgments, but only for the sake of architectonic symmetry. They have no meaning in Kant's context.