The Categories and The Need for a Transcendental Deduction in Kant’s Critique of Pure Reason

In the section of The Critique of Pure Reason by Immanuel Kant called the Transcendental Analytic, Kant endeavors to find what it is that we can know a priori that understanding will bring to the cognition of objects. In other words, he asks what are the concepts or judgements that we can know a priori will apply to any object that will be cognized or can be cognized by human beings? In this section, Kant is interested in finding what makes it possible for us to cognize objects, not from the view of sensibility, but from the view of the understanding. What are the pure concepts which are the condition of all thought? In the Metaphysical Deduction, Kant outlines 12 a priori concepts of the understanding called the categories which he argues are necessary for the cognition of objects. However, after showing how understanding is applied to objects in the form of the categories, Kant asserts that he has still not shown that such an application of a priori concepts to sensible objects is valid and leads to a meaningful perception of objective reality. In the Transcendental Aesthetic, Kant seeks to show this “objective validity” of the categories. Kant argues that as a priori concepts and necessary conditions for the possibility of experience, the categories will require a transcendental deduction in order to prove their validity and that an empirical deduction would be incapable of doing this.

In the Metaphysical Deduction, Kant sets out to identify the pure concepts which apply a priori to objects and which make the cognition of objects possible. Kant says that if we want a systematic way of identifying these pure concepts, we must first examine what the understanding is fundamentally. Kant argues that it is through this examination of the understanding that we can arrive at a list of pure concepts. Kant says that “the understanding in general can be represented as a faculty for judging” (A69/B94). According to Kant, judgment is a unity of concepts. When we make a judgment, what we are doing is unifying different concepts and we call this unity a judgment. Therefore, concepts are the elements out of which judgements are made and this is what Kant means when he says that concepts are “predicates of possible judgment” (A69/B94). Understanding, as the “faculty for judging,” is the faculty for using concepts since concepts are what we use to judge. Therefore, Kant argues that if we want to find the fundamental a priori concepts of cognition, that which makes it possible for us to think objects or apply concepts to what is given to us, what we need to understand is the ways in which these unities can be formed. Kant argues that we need to find all of the ways in which concepts can be unified into judgments, the basic functions of judgment itself completely abstracted away from any particular content, and he calls these the logical functions of unity and judgment. 

Kant argues that the “pure concepts of the understanding” or the categories are what we get when we apply these functions of understanding to objects that are given to us through sensible intuition. Therefore, the functions of the understanding, when taken up in transcendental logic and applied to objects, become the categories which, unlike the purely logical functions, have content. From the list of functions of the understanding, Kant derives a list of twelve fundamental concepts that our understanding must bring to bear in order to comprehend objects. Kant argues that these categories are built-in structures of the mind that shape our perception of reality. There are four main categories of pure concepts of the understanding: quantity, quality, relation, and modality. Quantity refers to the number of objects in consideration and includes the concepts of unity, plurality, and totality. Quality refers to the characteristics of objects in considerations and includes the concepts of reality, negation, and limitation. Relation refers to how objects can relate to one another and includes the concepts of substance, causation, and reciprocity. Lastly, modality refers to the conditions of objects and includes the concepts of possibility or impossibility, existence or non-existence, and necessity or contingency.

In the Metaphysical Deduction, Immanuel Kant shows that the categories are “subjective conditions of thinking.” That is, he argues that if the understanding is to be applied to objects, then we can know a priori that such an application is going to take the shape of the use of the categories. However, Kant still has not shown that the categories have “objective validity.” That is, he has not shown that the understanding does in fact get applied to objects or that its application to objects is legitimate. Given only the Metaphysical Deduction, it is still a possibility that objects “appear to us without their being under the necessity of being related to the functions of the understanding” (A89/B122). The legitimacy of applying the understanding to objects is what Kant hopes to show in the Transcendental Deduction: “I call the way in which concepts can relate to objects a priori their transcendental deduction and distinguish this from the empirical deduction which shows how a concept is acquired through experience and reflection on it” (A85/B118). 

Kant takes the word deduction from the German legal tradition. A deduction is a part of the legal argument that concerns the “entitlement or the legal claim” as opposed to the facts (A84/B116). He uses the word deduction because the argument is aimed at justifying the use of concepts in their application to objects. Unlike the empiricists and rationalists who came before him, Immanuel Kant is the first to draw a distinction between intuition and understanding. He is therefore the first to encounter a certain problem: how can these two separate things, intuition and understanding, come together? If it is truly the case, as Kant claims, that Intuition which in humans is sensibility and understanding which in humans is conceptual judgment, are separate things, then why would objects that are given to us through sensible intuition be the right kinds of things for our understanding to apply itself to? Kant himself suggests that if this problem is not solved, we ought to be suspicious of conceptual thought as it then could be the case that our concepts don’t apply to anything at all. Because objects are given to us in sensibility through intuition, showing the legitimacy of applying our pure concepts of the understanding to objects is essentially the same as bridging the gap between sensibility and understanding. To show that the application of the categories to objects of sensibility leads to a meaningful perception of objective reality is to show that the categories have “objective validity.” According to Kant, this is what the Transcendental Deduction is supposed to do. Without this, we would not be able to show that our knowledge of what we take to be reality is not simply a subjective construction. 

Kant argues that there are certain concepts such as “fate” and “fortune” which are arbitrary in that they lack justified application. Kant argues that he must show that the categories are not also arbitrary concepts. The categories require a transcendental deduction as opposed to an empirical deduction because they are a priori concepts of the understanding that are conditions for the possibility of empirical intuition. Therefore, they cannot be derived from empirical intuition. Kant uses the example of the concept of cause. While we can empirically observe repeated instances of similar events following other similar events and from there derive the concept of cause, this only tells us that one event will follow another, not that one event has caused another. In other words, an empirical deduction of a concept, like cause, would only speak to its subjective conditions and not its objective validity. An empirical deduction would be unable to show us that the concepts are necessary and universal: “Appearances may well offer cases from which a rule is possible in accordance with which something usually happens, but never a rule in accordance with which the succession is necessary” (A91/B124). In order to show that the pure concepts of the understanding like the concept of cause are necessary conditions for the possibility of experience, not a mental construct used to make sense of experience, the categories require a different kind of justification, a transcendental deduction not an empirical one: “the use of the pure concepts of the understanding would be entirely altered if one were to treat them only as empirical products” (A92/B124). Kant argues that a Transcendental Deduction must prove that “it is possible through [these concepts] alone to cognize something as an object” because the objective validity of the categories is contingent upon them being necessary conditions for the possibility of experience  (A92/B125). This is because the categories relate to objects of experience a priori meaning they must be prior to sensible experience and therefore what allows for it. 

In the Metaphysical Deduction, Immanuel Kant derives twelve pure concepts of the understanding which he calls the categories from the twelve logical functions of unity and judgment. These categories are the innate structures of the mind that allow for the possibility of sensible experience and shape our perception of reality. He argues that if the understanding is applied to objects, then it is done through these twelve categories. In the Transcendental Deduction, Kant wants to resolve what is still left unanswered by the Metaphysical Deduction. That is, Kant wants to show that it is valid to apply these categories to sensible objects and in doing so show how sensibility and the understanding interact. In order to show the objective validity of the categories and justify their application to objects, Kant argues that we need a transcendental deduction as an empirical deduction could only show the subjective conditions of a concept. The categories, as relating to objects a priori, require a transcendental deduction in order to show their objective validity as necessary conditions of sensible experience which form the structure of our coherent and meaningful perception of reality.