Critique of Pure Reason
Critique of Pure Reason
The Critique of Pure Reason (German: Kritik der reinen Vernunft, KrV) (1781; second edition 1787) is a book by Immanuel Kant that is considered one of the most influential works in the history of philosophy. Also referred to as Kant's First Critique, it was followed by the Critique of Practical Reason (1788) and the Critique of Judgment (1790).
In the preface to the first edition Kant explains what he means by critique of pure reason, stating "I do not mean by this a critique of books and systems, but of the faculty of reason in general, in respect of all knowledge after which it may strive independently of all experience."
The Critique is an investigation into the foundations and limits of human knowledge, and the extent to which the human mind is able to engage in metaphysics.
Kant builds on the work of empiricist philosophers such as John Locke and David Hume, as well as rationalists such as Gottfried Wilhelm Leibniz and Christian Wolff.
He expounds new ideas on the nature of space and time, and claims to provide solutions to Hume's scepticism regarding human knowledge of the relation of cause and effect, and René Descartes' scepticism regarding knowledge of the external world.
Kant claims to enact a 'Copernican revolution' in philosophy with his doctrine of transcendental idealism, according to which our knowledge does not "conform to objects", but rather objects "conform to our knowledge". According to Kant's doctrine, the human mind shapes and structures the world of experience, making knowledge possible.
Knowledge independent of experience Kant calls "a priori" knowledge, while knowledge obtained through experience is termed "a posteriori".
According to Kant, a proposition is a priori if it is necessary and universal. A proposition is necessary if it could not possibly be false, and so cannot be denied without contradiction. A proposition is universal if it is true in all cases, and so does not admit of any exceptions.
Knowledge gained a posteriori through the senses, Kant argues, never imparts absolute necessity and universality, because it is always possible that we might encounter an exception.
Kant claims to have discovered another attribute of propositions: the distinction between "analytic" and "synthetic" judgments.
According to Kant, a proposition is analytic if the content of the predicate-concept of the proposition is already contained within the subject-concept of that proposition. For example, Kant considers the proposition "All bodies are extended" analytic, since the predicate-concept ('extended') is already contained within—or "thought in"—the subject-concept of the sentence ('body'). The distinctive character of analytic judgements was therefore that they can be known to be true simply by an analysis of the concepts contained in them; they are true by definition.
In synthetic propositions, on the other hand, the predicate-concept is not already contained within the subject-concept. For example, Kant considers the proposition "All bodies are heavy" synthetic, since the concept 'body' does not already contain within it the concept 'weight'. Synthetic judgments therefore add something to a concept, whereas analytic judgments only explain what is already contained in the concept.
Prior to Kant, it was thought that all a priori knowledge must be analytic. Kant, however, argues that our knowledge of mathematics, of the first principles of natural science, and of metaphysics, is both a priori and synthetic. The peculiar nature of this knowledge, Kant argues, cries out for explanation. The central problem of the Critique is therefore to answer the question: "How are synthetic a priori judgements possible?" It is a "matter of life and death" to metaphysics and to human reason, Kant argues, that the grounds of this kind of knowledge be explained.
Critique of Pure Reason
The Critique of Pure Reason, after an introduction, is divided into two parts of very different lengths: A Transcendental Doctrine of Elements, running to almost 400 pages in a typical edition, followed by a Transcendental Doctrine of Method, which reaches scarcely 80 pages. The Elements deals with the sources of human knowledge, whereas the Method draws up a methodology for the use of “pure reason” and its a priori ideas. Both are “transcendental” in that they are presumed to analyze the roots of all knowledge and the conditions of all possible experience. The Elements is divided, in turn, into a Transcendental Aesthetic, a Transcendental Analytic, and a Transcendental Dialectic.
The simplest way of describing the contents of the Critique is to say that it is a treatise about metaphysics: it seeks to show the impossibility of one sort of metaphysics and to lay the foundations for another. The Leibnizian metaphysics, the object of Kant’s attack, is criticized for assuming that the human mind can arrive by pure thought at truths about entities which, by their very nature, can never be objects of experience, such as God, freedom, and immortality. Kant maintained, however, that the mind has no such power and that the vaunted metaphysics is thus a sham.
As Kant saw it, the problem of metaphysics, as indeed of any science, is to explain how, on the one hand, its principles can be necessary and universal and yet, on the other hand, involve also a knowledge of the real and so provide the investigator with the possibility of more knowledge than is analytically contained in what he already knows. To meet these two conditions, Kant maintained, knowledge must rest on judgments that are a priori, for it is only as they are separate from the contingencies of experience that they could be necessary and yet also synthetic—i.e., so that the predicate term contains something more than is analytically contained in the subject. ….. Hence, the basic problem, as Kant formulated it, is to determine “How [i.e., under what conditions] are synthetic a priori judgments possible?”
This problem arises, according to Kant, in three fields—mathematics, physics, and metaphysics—and the three main divisions of the first part of the Critique deal respectively with these.
In the Transcendental Aesthetic, Kant argued that mathematics necessarily deals with space and time and then claimed that these are both a priori forms of human sensibility that condition whatever is apprehended through the senses.
In the Transcendental Analytic, the most crucial as well as the most difficult part of the book, he maintained that physics is a priori and synthetic because in its ordering of experience it uses concepts of a special sort. These concepts—“categories,” he called them—are not so much read out of experience as read into it and, hence, are a priori, or pure, as opposed to empirical. But they differ from empirical concepts in something more than their origin: their whole role in knowledge is different. For, whereas empirical concepts serve to correlate particular experiences and so to bring out in a detailed way how experience is ordered, the categories have the function of prescribing the general form that this detailed order must take. They belong, as it were, to the very framework of knowledge. But although they are indispensable for objective knowledge, the sole knowledge that the categories can yield is of objects of possible experience; they yield valid and real knowledge only when they are ordering what is given through sense in space and time.
In the Transcendental Dialectic Kant turned to consideration of a priori synthetic judgments in metaphysics. Here, he claimed, the situation is just the reverse from what it is in mathematics and physics. Metaphysics cuts itself off from sense experience in attempting to go beyond it and, for this very reason, fails to attain a single true a priori synthetic judgment. To justify this claim, Kant analyzed the use that metaphysics makes of the concept of the unconditioned. Reason, according to Kant, seeks for the unconditioned or absolute in three distinct spheres: (1) in philosophical psychology, it seeks for an absolute subject of knowledge; (2) in the sphere of cosmology, it seeks for an absolute beginning of things in time, for an absolute limit to them in space, and for an absolute limit to their divisibility; and (3) in the sphere of theology, it seeks for an absolute condition for all things. In each case, Kant claimed to show that the attempt is doomed to failure by leading to an antinomy in which equally good reasons can be given for both the affirmative and the negative position. The metaphysical “sciences” of rational psychology, rational cosmology, and natural theology, familiar to Kant from the text of Baumgarten, on which he had to comment in his lectures, thus turn out to be without foundation.
With this work, Kant proudly asserted that he had accomplished a Copernican revolution in philosophy. Just as the founder of modern astronomy, Nicolaus Copernicus, had explained the apparent movements of the stars by ascribing them partly to the movement of the observers, so Kant had accounted for the application of the mind’s a priori principles to objects by demonstrating that the objects conform to the mind: in knowing, it is not the mind that conforms to things but instead things that conform to the mind.
Critique of Pure Reason
The Critique of Pure Reason (Kritik der reinen Vernunft), first published in 1781 with a second edition in 1787, is widely regarded as the most influential and widely read work of Immanuel Kant and one of the most influential and important in the entire history of Western philosophy. It is often referred to as Kant's "first critique," and was followed by the Critique of Practical Reason and the Critique of Judgment. Kant saw the first critique as an attempt to bridge the gap between rationalism and empiricism and, in particular, to counter the radical empiricism of David Hume.
Outline of the Critique of Pure Reason (CPR)
Kant’s starting point is what he calls the transcendental approach, i.e., an investigation into the a priori conditions of knowledge. Regardless of any particular experience, how can we know with absolute certainty that the knowledge we gain is true? Thus, the Critique of Pure Reason is an attempt to answer two questions: "What do we know?" and "How do we know it?" For Kant, trying to find a true answer to these questions empirically, by observing the world around us, was a hopeless undertaking destined to end in skepticism, as it did with Hume. Instead, it was necessary to first investigate our mind’s ability to know and to clearly establish its limits.
In short, Kant found that knowledge comes through us through two avenues: our sense perceptions in time and space, and our intellect’s cognitive forms (or categories), such as the notions of causality and existence, which give shape to these sense perceptions. Both are needed to reach knowledge. In Kant's words, "thoughts without content [are] empty, and intuitions without concepts [are] blind."
Kant argues that space and time are not part of what we might regard as objective reality, but are part of our apparatus of perception, and causality is a conceptual organizing principle that we impose upon nature. In other words, space and time are a ‘form’ of seeing and causality is a ‘form’ of knowing. Both space and time and our conceptual principles and processes pre-structure our experience.
Thus, things as they are "in themselves" are unknowable. For something to become an object of knowledge, it must be experienced, and experience is pre-structured by the activity of our own minds – both space and time as the forms of our intuition or perception, and the unifying, structuring activity of our concepts. These two aspects of our minds turn things-in-themselves into the world of our experience. We are never passive observers or knowers.
Kant's “I”—the Transcendental Unity of Apperception—is similarly unknowable. I am aware that there is an "I," subject, or self that accompanies all of my experience and consciousness. But since I only experience it in time, which is a "subjective" form of perception, I can never know directly that "I" that is appearing in time as it might be "in itself," outside of time. Thus we can never truly know ourselves as we might be outside of or prior to the forms through which we perceive and conceive ourselves.
This provided Kant with the basis to distinguish between phenomena – things as they appear to our senses (including the inner sense of time) – and noumena or things in themselves – things that are purely objects of thought independently of sense perception, which, by definition, we can never experience.
Structure of the CPR
In the structure of the CPR, the Transcendental Aesthetic is the section that considers the contribution of intuition to our knowledge or cognition. By aesthetics, Kant refers to the study of our sense perceptions; by intuition, he simply means the capacity of our senses to perceive.
The Transcendental Logic is that part of the CPR where Kant investigates the understanding and its role in constituting our knowledge. The understanding is defined as the faculty of the mind that deals with concepts. The Logic is divided into two parts: the Analytic and the Dialectic. In the Analytic Kant investigates the contributions of the understanding (Verstand) to knowledge. In the Dialectic Kant investigates the limits of reason (Vernunft).
Certainty and limits of our knowledge
The result of the CPR is twofold: first, we are certain that knowledge can be true within the parameters of our own mind. We know that things do exist in time and space and that they follow the law of cause and effect and similar laws, but only “to the extent that they appear to us,” i.e., as phenomena. Second, we can never know what things are in themselves. Furthermore, we can never say anything meaningful about those things that do not exist within the framework of our sense perception, e.g., God and the immortality of the soul. The good news, says Kant, is that it is also utterly impossible to disprove their existence. These things are not part of our world and we can say nothing about them. The last part of the CPR contains a lengthy discussion of the ways in which the mind is led astray when it tries, as traditional metaphysics does, to prove or disprove truths about these transcendent objects. The so-called “Paralogisms” and “Antinomies” are meant to show that, when it speaks about what it can’t know, our reason ends up in insurmountable contradictions, e.g., proving at the same time that the world must have had a beginning and that it cannot have had one.
The noumenon exists as the horizon of our experience of a thing, a horizon that can only be circumscribed with philosophical concepts. Kant's whole metaphysical system, which is based on the operations of cognitive faculties, was meant to describe the world as we experience it—a much more modest task than describing the world as it is beyond our experience of it, which, according to Kant, is what all previous philosophy was mistakenly trying to do.
Problem areas and issues in the CPR
The CPR and Kant’s epistemology in general are immensely complex. Kant himself somewhat immodestly said that the central part of his deduction was the most difficult task ever undertaken in philosophy. Two central points of contention stand out. First, Kant did believe that there was a reality. He strongly disapproved of Berkeley’s subjective idealism, for which reality only exists through the perception of the mind. In the second edition of the CPR, Kant added an entire section destined to show that the world exists. His critique is merely saying is that we cannot know what it outside of our perception, but that it does exist is not in doubt. To what extent Kant can justify this position from his premises is questionable.
Second, the notion of the Ding an sich, the unknowable thing in itself, is very problematic. Considerable difficulties arise each time Kant attempts to say something about it after affirming that nothing can be meaningfully said. This is the case when Kant hints to the fact that things in themselves are somehow the ground of the phenomenal world. Since the two realms are supposed to be separated by an unbridgeable abyss, such a suggestion is not really supportable, except by appealing to a sort of intuition that Kant himself rejects. Jacobi was the first to highlight this problem. Nevertheless, the noumenon or thing in itself is a fertile notion, in that it implies that reality is more than merely what it appears to be.
Kant's Copernican revolution in philosophy
Kant's strategy in the Critique (1781) is similar to that of the Inaugural Dissertation (1770) in that both works attempt to reconcile modern science with traditional morality and religion by relegating them to distinct sensible and intelligible worlds, respectively. But the Critique gives a far more modest and yet revolutionary account of a priori knowledge. As Kant's letter to Herz suggests, the main problem with his view in the Inaugural Dissertation is that it tries to explain the possibility of a priori knowledge about a world that is entirely independent of the human mind. This turned out to be a dead end, and Kant never again maintained that we can have a priori knowledge about an intelligible world precisely because such a world would be entirely independent of us.
Kant's revolutionary position in the Critique is that we can have a priori knowledge about the general structure of the sensible world because it is not entirely independent of the human mind. The sensible world, or the world of appearances, is constructed by the human mind from a combination of sensory matter that we receive passively and a priori forms that are supplied by our cognitive faculties. We can have a priori knowledge only about aspects of the sensible world that reflect the a priori forms supplied by our cognitive faculties. In Kant's words, “we can cognize of things a priori only what we ourselves have put into them”. So according to the Critique, a priori knowledge is possible only if and to the extent that the sensible world itself depends on the way the human mind structures its experience.
Kant characterizes this new constructivist view of experience in the Critique through an analogy with the revolution wrought by Copernicus in astronomy:
Up to now it has been assumed that all our cognition must conform to the objects; but all attempts to find out something about them a priori through concepts that would extend our cognition have, on this presupposition, come to nothing. Hence let us once try whether we do not get farther with the problems of metaphysics by assuming that the objects must conform to our cognition, which would agree better with the requested possibility of an a priori cognition of them, which is to establish something about objects before they are given to us. This would be just like the first thoughts of Copernicus, who, when he did not make good progress in the explanation of the celestial motions if he assumed that the entire celestial host revolves around the observer, tried to see if he might not have greater success if he made the observer revolve and left the stars at rest. Now in metaphysics we can try in a similar way regarding the intuition of objects. If intuition has to conform to the constitution of the objects, then I do not see how we can know anything of them a priori; but if the object (as an object of the senses) conforms to the constitution of our faculty of intuition, then I can very well represent this possibility to myself. Yet because I cannot stop with these intuitions, if they are to become cognitions, but must refer them as representations to something as their object and determine this object through them, I can assume either that the concepts through which I bring about this determination also conform to the objects, and then I am once again in the same difficulty about how I could know anything about them a priori, or else I assume that the objects, or what is the same thing, the experience in which alone they can be cognized (as given objects) conforms to those concepts, in which case I immediately see an easier way out of the difficulty, since experience itself is a kind of cognition requiring the understanding, whose rule I have to presuppose in myself before any object is given to me, hence a priori, which rule is expressed in concepts a priori, to which all objects of experience must therefore necessarily conform, and with which they must agree.
As this passage suggests ….. the Critique claims that pure understanding, rather than giving us insight into an intelligible world, is limited to providing forms — which he calls pure or a priori concepts — that structure our cognition of the sensible world. So now both sensibility and understanding work together to construct cognition of the sensible world, which therefore conforms to the a priori forms that are supplied by our cognitive faculties: the a priori intuitions of sensibility and the a priori concepts of the understanding. This account is analogous to the heliocentric revolution of Copernicus in astronomy because both require contributions from the observer to be factored into explanations of phenomena, although neither reduces phenomena to the contributions of observers alone. The way celestial phenomena appear to us on earth, according to Copernicus, is affected by both the motions of celestial bodies and the motion of the earth, which is not a stationary body around which everything else revolves. For Kant, analogously, the phenomena of human experience depend on both the sensory data that we receive passively through sensibility and the way our mind actively processes this data according to its own a priori rules. These rules supply the general framework in which the sensible world and all the objects (or phenomena) in it appear to us. So the sensible world and its phenomena are not entirely independent of the human mind, which contributes its basic structure.
How does Kant's Copernican revolution in philosophy improve on the strategy … for reconciling modern science with traditional morality and religion? First, it gives Kant a new and ingenious way of placing modern science on an a priori foundation. He is now in a position to argue that we can have a priori knowledge about the basic laws of modern science because those laws reflect the human mind's contribution to structuring our experience. In other words, the sensible world necessarily conforms to certain fundamental laws — such as that every event has a cause — because the human mind constructs it according to those laws. Moreover, we can identify those laws by reflecting on the conditions of possible experience, which reveals that it would be impossible for us to experience a world in which, for example, any given event fails to have a cause. From this Kant concludes that metaphysics is indeed possible in the sense that we can have a priori knowledge that the entire sensible world — not just our actual experience, but any possible human experience — necessarily conforms to certain laws. Kant calls this immanent metaphysics or the metaphysics of experience, because it deals with the essential principles that are immanent to human experience.
But, second, if “we can cognize of things a priori only what we ourselves have put into them,” then we cannot have a priori knowledge about things whose existence and nature are entirely independent of the human mind, which Kant calls things in themselves. …… That is, Kant's constructivist foundation for scientific knowledge restricts science to the realm of appearances and implies that a priori knowledge of things in themselves that transcend possible human experience — or transcendent metaphysics — is impossible. …… …….
In the Critique Kant … claims that rejecting knowledge about things in themselves is necessary for reconciling science with traditional morality and religion. This is because he claims that belief in God, freedom, and immortality have a strictly moral basis, and yet adopting these beliefs on moral grounds would be unjustified if we could know that they were false. “Thus,” Kant says, “I had to deny knowledge in order to make room for faith”. Restricting knowledge to appearances and relegating God and the soul to an unknowable realm of things in themselves guarantees that it is impossible to disprove claims about God and the freedom or immortality of the soul, which moral arguments may therefore justify us in believing. Moreover, the determinism of modern science no longer threatens the freedom required by traditional morality, because science and therefore determinism apply only to appearances, and there is room for freedom in the realm of things in themselves, where the self or soul is located. We cannot know (theoretically) that we are free, because we cannot know anything about things in themselves. But there are especially strong moral grounds for the belief in human freedom, which acts as “the keystone” supporting other morally grounded beliefs. In this way, Kant replaces transcendent metaphysics with a new practical science that he calls the metaphysics of morals. It thus turns out that two kinds of metaphysics are possible: the metaphysics of experience (or nature) and the metaphysics of morals, both of which depend on Kant's Copernican revolution in philosophy.
Transcendental idealism
A doctrine that the objects of perception are conditioned by the nature of the mind.
Transcendental idealism is the theory that emphasizes the subjective conditions on the possibility of meaningful experience. Thus, our meaningful experiences are in some sense mind-dependent.
Kant uses the term “transcendental” to emphasize the conditions independent of senses that incorporate in and make our experience orderly and meaningful.
He uses the term “idealism” to indicate that our meaningful experiences are in some sense mind-dependent.
The fundamental theses of transcendental idealism include:
1. Space and time are a priori, subjective conditions without which an orderly experience would be impossible.
2. The ‘categoreal’ concepts are innate ideas independent of experience but without which a meaningful experience would be impossible.
3. We can only know things that can be experienced, objects and events that conform to the transcendental conditions of experience. Hence, we can only know things as they appear in experience, not things in themselves.
Perhaps the central and most controversial thesis of the Critique of Pure Reason is that human beings experience only appearances, not things in themselves; and that space and time are only subjective forms of human intuition that would not subsist in themselves if one were to abstract from all subjective conditions of human intuition. Kant calls this thesis transcendental idealism. One of his best summaries of it is arguably the following:
We have therefore wanted to say that all our intuition is nothing but the representation of appearance; that the things that we intuit are not in themselves what we intuit them to be, nor are their relations so constituted in themselves as they appear to us; and that if we remove our own subject or even only the subjective constitution of the senses in general, then all constitution, all relations of objects in space and time, indeed space and time themselves would disappear, and as appearances they cannot exist in themselves, but only in us. What may be the case with objects in themselves and abstracted from all this receptivity of our sensibility remains entirely unknown to us. We are acquainted with nothing except our way of perceiving them, which is peculiar to us, and which therefore does not necessarily pertain to every being, though to be sure it pertains to every human being. We are concerned solely with this. Space and time are its pure forms, sensation in general its matter. We can cognize only the former a priori, i.e., prior to all actual perception, and they are therefore called pure intuition; the latter, however, is that in our cognition that is responsible for its being called a posteriori cognition, i.e., empirical intuition. The former adheres to our sensibility absolutely necessarily, whatever sort of sensations we may have; the latter can be very different. (A42/B59–60)
Kant introduces transcendental idealism in the part of the Critique called the Transcendental Aesthetic, and scholars generally agree that for Kant transcendental idealism encompasses at least the following claims:
•In some sense, human beings experience only appearances, not things in themselves.
•Space and time are not things in themselves, or determinations of things in themselves that would remain if one abstracted from all subjective conditions of human intuition. It is at least a crucial part of what he means by calling space and time transcendentally ideal.
•Space and time are nothing other than the subjective forms of human sensible intuition.
•Space and time are empirically real, which means that “everything that can come before us externally as an object” is in both space and time, and that our internal intuitions of ourselves are in time.
But scholars disagree widely on how to interpret these claims, and there is no such thing as the standard interpretation of Kant's transcendental idealism. Two general types of interpretation have been especially influential, however. This section provides an overview of these two interpretations, although it should be emphasized that much important scholarship on transcendental idealism does not fall neatly into either of these two camps: 1, The two-objects interpretation. 2. The two-aspects interpretation.
According to “two-world” interpretations, the distinction between appearances and things in themselves is to be understood in metaphysical and ontological terms. Appearances (and hence the entire physical world that we experience) comprise one set of entities, and things in themselves are an ontologically distinct set of entities. Although things in themselves may somehow cause us to have experience of appearances, the appearances we experience are not things in themselves.
According to “one-world” or “two-aspect” interpretations, the distinction between appearances and things in themselves is to be understood in epistemological terms. Appearances are ontologically the very same things as things in themselves, and the phrase “in themselves” simply means “not considered in terms of their epistemic relation to human perceivers.”
A common objection against two-world interpretations is that they may make Kant’s theory too similar to Berkeley’s immaterialist idealism (an association from which Kant vehemently tried to distance himself), and they seem to ignore Kant’s frequent characterization of the appearance/thing in itself distinction in terms of different epistemic standpoints. And a common objection against one-world interpretations is that they may trivialize some of the otherwise revolutionary aspects of Kant’s theory, and they seem to ignore Kant’s frequent characterization of the appearance/thing in itself distinction in seemingly metaphysical terms. There have been attempts at interpretations that are intermediate between these two options. For instance, some have argued that Kant only acknowledges one world, but that the appearance/thing in itself distinction is nevertheless metaphysical, not merely epistemological.
Transcendental Deduction
Summary
Kant sets out in the Transcendental Deduction to prove that we have a priori concepts or categories which are objectively valid and which are a necessary condition of our synthetic experience of the world. He does this by deriving the synthetic nature of our understanding from the unity of apperception, and then basing the objectivity of understanding on the perceptual distinction between subject and object made possible by the unity of apperception. Kant then turns to the concept of judgment, defining it as objective in that judgments are descriptions of objects independent of subjects. However, judgments must be based upon a priori categories or they would not be understandable, and hence would not be judgments. Therefore, the a priori categories exist, and they are objectively valid and a necessary condition of our synthetic understanding.
Introduction
The goal of the Transcendental Deduction is to prove that we have a priori concepts or categories which are objectively valid and which are a necessary condition of our experience of the world. As Kant puts it, “The objective validity of the categories as a priori concepts rests, therefore, on the fact that, so far as the form of thought is concerned, through them alone does experience become possible.” (B 126) ……. Kant argues that the twelve categories exist a priori in the understanding and make synthesis of manifold representations possible. Kant explains: “By synthesis, in its most general sense, I understand the act of putting different representations together, and of grasping what is manifold in them in one [act of] knowledge.” (B 103) In other words, synthesis is the process by which the mind takes multiple representations, or a manifold, and connects them with one another according to the categories, producing a single broader representation of the manifold. Kant will present three arguments in support of the Transcendental Deduction. First, the synthetic nature of the understanding can be derived from the unity of pure apperception. Second, our objective representations must be necessary and universal, and hence a priori rather than empirical. Third, we use a priori categories in judgment to distinguish between subjective and objective representations.
The Unity of Transcendental Apperception
Apperception, to Kant, is self-consciousness, or the awareness of one’s own mind. As Kant defines it, “…it is that self-consciousness which, while generating the representation ‘I think’ (a representation which must be capable of accompanying all other representations, and which in all consciousness is one and the same), cannot itself be accompanied by any further representation.” (B 132)
[Thus] Kant describes apperception as single unified identity, the ‘I think’.
“…… a manifold which is given in intuition contains a synthesis of representation, and is possible only through the consciousness of this synthesis.” (B 133)
Thus, the synthetic nature of apperception is perceived in oneself as we synthesize representations. In other words, the synthetic nature of the understanding can be derived from the unity of pure apperception.
A Priori Objective Representations
Next Kant distinguishes between subjective and objective conceptions of a manifold representation. Kant describes a subjective representation as, “…a determination of inner sense through which the manifold of intuition for such combination is empirically given. Whether I can become empirically conscious of the manifold as simultaneous or as successive depends on circumstances or empirical conditions.” (B 139)
In other words, were representations of manifolds to rely upon empirical associations -- the simultaneity of time or the succession of space -- they would fail to be objective, since empirical associations in time and space change.
Kant offers an alternative to these subjective, empirical associations: “The transcendental unity of apperception is that unity through which all the manifold given in an intuition is united in a concept of the object. It is therefore entitled objective.” (B 139)
By this Kant means a representation is objective when, rather than seeking a manifold within empirical associations, we allow the manifold ordering of representations to occur within our unified apperception.
Focusing on the pure intuition of time, Kant puts it thus: “But the pure form of intuition in time…which contains a given manifold, simply through the necessary relation of the manifold of the intuition to the one ‘I think’, and so through the pure synthesis of understanding which is the a priori underlying unity of objectivity is valid.” (B 140)
As Kant states elsewhere, time and space are pure a priori forms of intuition. Therefore, if a manifold is perceived in space and time, it is the necessary application of the unity of apperception which results in an a priori distinction between the object and the ‘I think’ self. Kant interprets this process as necessarily and objectively valid in that the object of perception is clearly distinguished from the perceiver, and thus is inherently objective rather than empirically subjective.
Judgment and the A Priori Categories
Kant uses the term judgment to explain the process of distinguishing objective connections between representations from subjective associations. “…I find that a judgment is nothing but the manner in which given modes of knowledge are brought to the objective unity of apperception.” (B 141) This definition of judgment is therefore closely related to synthesis, as described above. Judgment is combining a subject with a predicate, as in Kant’s example, ‘the body is heavy’. Notice that this judgment is objective in the sense that it is attributing heaviness to an object independent of the perceiving subject.
Kant offers a helpful example which helps illustrate his explanation of judgment. “When…I perceive the freezing of water, I apprehend two states, fluidity and solidity, and these as standing to one another in a relation of time. But in time, which I place at the appearance [in so far] as [it is] inner intuition, I necessarily represent to myself synthetic unity of the manifold, without which that relation of time could not be given in an intuition as being determined in respect of time-sequence…the category of cause, by means of which, when I apply it to my sensibility, I determine everything that happens in accordance with the relation which it prescribes, and I do so in time in general.” (B 163)
In other words, it is the a priori form of time which allows the perception of both the fluid and solid water as a single synthetic manifold, and judgment according to an a priori category, in this case ‘cause [and effect]’, which makes the synthetic relation between the representations of water and ice understandable. Thus the categories are a priori, rather than the result of empirical perceptions, else they would not be available to form the very judgments which make understanding possible.
The transcendental deduction
The goal of the transcendental deduction is to show that we have a priori concepts or categories that are objectively valid, or that apply necessarily to all objects in the world that we experience. To show this, Kant argues that the categories are necessary conditions of experience, or that we could not have experience without the categories. In Kant's words:
[T]he objective validity of the categories, as a priori concepts, rests on the fact that through them alone is experience possible (as far as the form of thinking is concerned). For they then are related necessarily and a priori to objects of experience, since only by means of them can any object of experience be thought at all.
The transcendental deduction of all a priori concepts therefore has a principle toward which the entire investigation must be directed, namely this: that they must be recognized as a priori conditions of the possibility of experiences (whether of the intuition that is encountered in them, or of the thinking). Concepts that supply the objective ground of the possibility of experience are necessary just for that reason. (A93–94/B126)
The strategy Kant employs to argue that the categories are conditions of experience is the main source of both the obscurity and the ingenuity of the transcendental deduction. His strategy is to argue that the categories are necessary specifically for self-consciousness, for which Kant often uses the Leibnizian term “apperception.”
1. Self-consciousness
What is the source of our sense of an ongoing and invariable self that persists throughout all the changes in our experience? ………….. ………………. ………………
2. Objectivity and judgment
The next condition is that self-consciousness requires me to represent an objective world distinct from my subjective representations. ………….. ………………. ………………
3. The law-giver of nature
The final condition of self-consciousness that Kant adds to the preceding conditions is that our understanding must cooperate with sensibility to construct one, unbounded, and unified space-time to which all of our representations may be related. ………….. ………………. ………………
The Deduction of the Categories
The task of the chapter titled “Transcendental Deduction of the Categories” is to show that these categories can and must be applied in some way to any object that could possibly be an object of experience. …………
Kant’s argument turns on conceptions of self-consciousness (or what he calls “apperception”) as a condition on the possibility of experiencing the world as a unified whole. Kant takes it to be uncontroversial that we can be aware of our representations as our representations. It is not just that I can have the thoughts ‘P’ or ‘Q’; I am also always able to ascribe these thoughts to myself: ‘I think P’ and ‘I think Q’. Further, we are also able to recognize that it is the same I that does the thinking in both cases. Thus, we can recognize that ‘I think both P and Q’. In general, all of our experience is unified because it can be ascribed to the one and same I, and so this unity of experience depends on the unity of the self-conscious I.
Kant next asks what conditions must obtain in order for this unity of self-consciousness to be possible. His answer is that we must be able to differentiate between the I that does the thinking and the object that we think about. That is, we must be able to distinguish between subjective and objective elements in our experience. If we could not make such a distinction, then all experience would just be so many disconnected mental happenings: everything would be subjective and there would be no “unity of apperception” that stands over and against the various objects represented by the I. So next Kant needs to explain how we are able to differentiate between the subjective and objective elements of experience. His answer is that a representation is objective when the subject is necessitated in representing the object in a certain way, that is, when it is not up to the free associative powers of my imagination to determine how I represent it. For instance, whether I think a painting is attractive or whether it calls to mind an instance from childhood depends on the associative activity of my own imagination; but the size of the canvas and the chemical composition of the pigments is not up to me: insofar as I represent these as objective features of the painting, I am necessitated in representing them in a certain way. In order for a representational content to be necessitated in this way, according to Kant, is for it to be subject to a “rule.” The relevant rules that Kant has in mind are the conditions something must satisfy in order for it to be represented as an object at all. And these conditions are precisely the concepts laid down in the schema of the categories, which are the concepts of an “object in general.” Hence, if I am to have experience at all, I must conceptualize objects in terms of the a priori categories.
Kant’s argument in the Deduction is a “transcendental argument”: Kant begins with a premise accepted by everyone, but then asks what conditions must have been met in order for this premise to be true. Kant assumed that we have a unified experience of the many objects populating the world. This unified experience depends on the unity of apperception. The unity of apperception enables the subject to distinguish between subjective and objective elements in experience. This ability, in turn, depends on representing objects in accordance with rules, and the rules in question are the categories. Hence, the only way we can explain the fact that we have experience at all is by appeal to the fact that the categories apply to the objects of experience.
It is worth emphasizing how truly radical the conclusion of the Transcendental Deduction is. Kant takes himself to have shown that all of nature is subject to the rules laid down by the categories. But these categories are a priori: they originate in the mind. This means that the order and regularity we encounter in the natural world is made possible by the mind’s own construction of nature and its order. Thus the conclusion of the Transcendental Deduction parallels the conclusion of the Transcendental Aesthetic: where the latter had shown that the forms of sensibility (space and time) originate in the mind and are imposed on the world, the former shows that the forms of understanding (the categories) also originate in the mind and are imposed on the world.
Critique of Pure Reason
(Excerpt and condensation from Will Durant's The Story of Philosopy)
What is meant by this title? Critique is not precisely a criticism, but a critical analysis; Kant is not attacking “pure reason”, except, at the end, to show its limitations; rather he hopes to show its possibility, and to exalt it above the impure knowledge which comes to us through the distorting channels of sense. For “pure” reason is to mean knowledge that does not come through our senses, but is independent of all sense experience; knowledge belonging to us by the inherent nature and structure of the mind.
At the very outset, then, Kant flings down a challenge to Locke and the English school; knowledge is not all derived from the senses. Hume thought he had shown that there is no soul, and no science; that our minds are but our ideas in procession and association; and our certainties but probabilities in perpetual danger of violation. These false conclusions, says Kant, are the result of false premises: you assume that all knowledge comes from “separate and distinct sensations; naturally these cannot give you necessity, or invariable sequences of which you may be forever certain; …. Let us grant that absolute certainty of knowledge is impossible if all knowledge comes from sensation, from an independent external world which owes us no promise of regularity of behavior. But what if we have knowledge that is independent of sense-experience, knowledge whose truth is certain to us even before experience - a priori? Then absolute truth, and absolute science, would become possible, would it not? Is there such absolute knowledge? This is the problem of the first Critique. …… The Critique becomes a detailed biology of thought, and examination of the origin and evolution of concept, and analysis of the inherited structure of the mind. ……
…… Experience never gives us any really general truths; …… general truths must be independent of experience – clear and certain in themselves. ……
Mathematical knowledge is necessary and certain. ….. But whence do we get this character of absoluteness and necessary? … These truths derive their necessary character from the inherent structure of our minds, from the natural and inevitable manner in which our minds must operate. For the mind of man is not passive wax upon which experience and sensation write their absolute and yet whimsical will; nor is it a mere abstract name for the series or group of mental states; it is an active organ which moulds and coordinates sensations into ideas, an organ which transforms the chaotic multiplicity of experience into the ordered unity of thought.
But how?
The effort to answer this question, to study the inherent structure of the mind, or the innate laws of thought, is what Kant calls “transcendental philosophy”, because it is a problem transcending sense-experience. ….
There are two grades or stages in this process of working up the raw material of sensation into the finished product of thought.
The first stage is the coordination of sensations by applying to them the forms of perception – space and time; the second stage is the coordination of the perceptions so developed, by applying to them the forms of conception – the “categories” of thought.
Kant, using the word esthetic in its original and etymological sense, as connoting sensation or feeling, calls the study of the first of these stages “Transcendental Esthetic”; and using the word logic as meaning the science of the forms of thought, he calls the study of the second stage “Transcendental Logic”. …..
1. Transcendental Esthetic
What is meant by sensations and perceptions? – and how does the mind change the former into the latter?
By itself a sensation is merely the awareness of a stimulus; we have a taste on the tongue, an odor in the nostrils, a sound in the ears, a temperature on the skin, a flash of light on the retina, a pressure on the fingers: it is the raw crude beginning of experience; it is what the infant has in the early days of its groping mental life; it is not yet knowledge.
But let these various sensations group themselves about an object in space and time – say this apple; let the odor in the nostrils, and the taste on the tongue, the light on the retina, the shape-revealing pressure on the fingers and the hand, unite and group themselves about this “thing”: and there is now an awareness not so much of a stimulus as of a specific object; there is a perception. Sensation has passed into knowledge.
But again, was this passage, this grouping, automatic? Did the sensations of themselves, spontaneously and naturally, fall into a cluster and an order, and so become perception? Yes, said Locke and Hume; not at all, says Kant.
For these varied sensations come to us through varied channels of sense, through a thousand “afferent nerves” that pass from skin and eye and ear and tongue into the brain; what a medley of messengers they must be as they crowd into the chambers of the mind, calling for attention! No wonder Plato spoke of “the rabble of the senses”. And left to themselves, they remain rabble, a chaotic “manifold”, pitifully impotent, waiting to be ordered into meaning and purpose and power. As readily might the messages brought to a general from a thousand sectors of the battle-line weave themselves unaided into comprehension and command. No; there is a law-giver for this mob, a directing and coordinating power that does not merely receive, but takes these atoms of sensation and moulds them into sense.
Observe, first, that not all the messages are accepted. ….. Only those sensations are selected that can be moulded into perceptions suited to your present purpose, or that bring those imperious messages of danger which are always relevant. ……. Association of sensations … is above all determined by the purpose of the mind.
The agent of selection and coordination is the mind, which, Kant thinks, uses first of all two simple methods for the classification of the material presented to it: the sense of space, and the sense of time. …. The mind allocates its sensations in space and time, attributes them to this thing here or that thing there, to this present time or to that past. Space and time are not things perceived, but modes of perception, ways of putting sense into sensation; space and time are organs of perception.
They are a priori, because all ordered experience involves and presupposes them. Without them, sensations could never grow into perceptions. They are a priori because it is inconceivable that we should ever have any future experience that will not also involve them. And because they are a priori, their laws, which are the laws of mathematics, are a priori, absolute and necessary, world without end. It is not merely probable, it is certain that we shall never find a straight line that is not the shortest distance between two points. Mathematics is saved.
Can all the sciences be similarly saved? Yes, if their basic principle. The law of causality – that a given cause must always be followed by a given effect – can be shown, like space and time, to be so inherent in all processes of understanding that no future experience can be conceived that would violate or escape it. Is causality, too, a priori, an indispensable prerequisite and condition of all thought?
2. Transcendental Analytic
The second stage is the coordination of the perceptions so developed, by applying to them the forms of conception – the “categories” of thought …. which raise the "perceptual" knowledge of objects into the "conceptual" knowledge of relationships, sequences, and laws ; those tools of the mind which refine experience into science. Just as perceptions arranged sensations around objects in space and time, so conception arranges perceptions (objects and events) about the ideas of cause, unity, reciprocal relation, necessity, contingency, etc.; these and other "categories" are the structure into which perceptions are received, and by which they are classified and moulded into the ordered concepts of thought. These are the very essence and character of the mind; mind is the coordination of experience.
………… …………….. ……………..
Sensation is unorganized stimulus, perception is organized sensation, conception is organized perception, science is organized knowledge, wisdom is organized life: each is a greater degree of order, and sequence, and unity. Whence this order, this sequence, this unity? Not from the things themselves; for they are known to us only by sensations that Come through a thousand channels at once in disorderly multitude; it is our purpose that put order and sequence and unity upon this importunate lawlessness; it is ourselves, our personalities, our minds, that bring light upon these seas.
Locke was wrong when he said, There is nothing in the intellect except what was first in the senses"; Leibnitz was right when he added,—"nothing, except the intellect itself." "Perceptions without conceptions," says Kant, "are blind." If perceptions wove themselves automatically into ordered thought, if mind were not an active effort hammering out order from chaos, how could the same experience leave one man mediocre, and in a more active and tireless soul be raised to the light of wisdom and the beautiful logic of truth?
The world, then, has order, not of itself, but because the thought that knows the world is itself an ordering; the first stage in that classification of experience which at last is science and philosophy.
The laws of thought are also the laws of things, for things are known to us only through this thought that must obey these laws, since it and they are one; in effect, as Hegel was to say, the laws of logic and the laws of nature are one, and logic and metaphysics merge. The generalized principles of science are necessary because they are ultimately laws of thought that are involved and presupposed in every experience, past, present, and to come. Science is absolute, and truth is everlasting.
3. Transcendental Dialectic
Nevertheless, this certainty, this absoluteness, of the highest generalizations of logic and science, is, paradoxically, limited and relative: limited strictly to the field of actual experience, and relative strictly to our human mode of experience. For if our analysis has been correct, the world as we know it is a construction, a finished product, almost—one might say—a manufactured article, to which the mind contributes as much by its moulding forms as the thing contributes by its stimuli. (So we perceive the top of the table as round, whereas our sensation is of an ellipse.)
The object as it appears to us is a phenomenon, an appearance, perhaps very different from the external object before it came within the ken of our senses; what that original object was we can never know; the "thing-in-itself" may be an object of thought or inference (a “noumenon"), but it cannot be experienced,—for in being experienced it would be changed by its passage through sense and thought. "It remains completely unknown to us what objects maybe by themselves and apart from the receptivity of our senses. We know nothing but our manner of perceiving them; that manner being peculiar to us, and not necessarily shared by every being, though, no doubt, by every human being." The moon as known to us is merely a bundle of sensations (as Hume saw), unified (as Hume did not see) by our native mental structure through the elaboration of sensations into perceptions, and of these into conceptions or ideas; in result, the moon is for us merely our ideas.
Not that Kant ever doubts the existence of "matter" and the external world; but he adds that we know nothing certain about them except that they exist. Our detailed knowledge is about their appearance, their phenomena, about the sensations which we have of them. Idealism does not mean, as the man in the street thinks, that nothing exists outside the perceiving subject; but that a goodly part of every object is created by the forms of perception and understanding: we know the object as transformed into idea; what it is before being so transformed we cannot know. Science, after all, is naive; it supposes that it is dealing with things in themselves, in their full-blooded external and uncorrupted reality; philosophy is a little more sophisticated, and realizes that the whole material of science consists of sensations, perceptions and conceptions, rather than of things. "Kant's greatest merit," says Schopenhauer," is the distinction of the phenomenon from the thing-in-itself."
It follows that any attempt, by either science or religion, to say just what the ultimate reality is, must fallback into mere hypothesis; "the understanding can never go beyond the limits of sensibility." Such transcendental science loses itself in "antinomies," and such transcendental theology loses itself in "paralogisms." It is the cruel function of "transcendental dialectic" to examine the validity of these attempts of reason to escape from the enclosing circle of sensation and appearance into the unknowable world of things "in themselves,"
Antinomies are the insoluble dilemmas born of a science that tries to overleap experience. So, for example, when knowledge attempts to decide whether the world is finite or infinite in space, thought rebels against either supposition: beyond any limit, we are driven to conceive something further, endlessly; and yet infinity is itself inconceivable. Again: did the world have a beginning in time? We cannot conceive eternity; but then, too, we cannot conceive any point in the past without feeling at once that before that, something was. Or has that chain of causes which science studies, a beginning, a First Cause? Yes, for an endless chain is inconceivable; no, for a first cause uncaused is inconceivable as well.
Is there any exit from these blind alleys of thought? There is, says Kant, if we remember that space, time and cause are modes of perception and conception, which must enter into all our experience, since they are the web and structure of experience; these dilemmas arise from supposing that space, time and cause are external things independent of perception. We shall never have any experience which we shall not interpret in terms of space and time and cause; but we shall never have any philosophy if we forget that these are not things, but modes of interpretation and understanding.
So with the paralogisms of "rational" theology-—which attempts to prove by theoretical reason that the soul is an incorruptible substance, that the will is free and above the law of cause and effect, and that there exists a "necessary being," God, as the presupposition of all reality. Transcendental dialectic must remind theology that substance and cause and necessity are finite categories, modes of arrangement and classification which the mind applies to sense-experience, and reliably valid only for the phenomena that appear to such experience; we cannot apply these conceptions to the noumenal (or merely inferred and conjectural) world. Religion cannot be proved by theoretical reason.
So the first Critique ends. One could well imagine David Hume, un-cannier Scot than Kant himself, viewing the results with a sardonic smile. Here was a tremendous book, eight hundred pages long; weighted beyond bearing, almost, with ponderous terminology; proposing to solve all the problems of metaphysics, and incidentally to save the absoluteness of science and the essential truth of religion. What had the book really done? It had destroyed the naive world of science, and limited it, if not in degree, certainly in scope,—and to a world confessedly of mere surface and appearance, beyond which it could issue only in farcical "antinomies"; so science was" saved"! The most eloquent and incisive portions of the book had argued that the objects of faith—a free and immortal soul, a benevolent creator—could never be proved by reason; so religion was "saved"! No wonder the priests of Germany protested madly against this salvation, and revenged themselves by calling their dogs Immanuel Kant.
And no wonder that Heine compared the little professor of Königsberg with the terrible Robespierre; the latter had merely killed a king, and a few thousand Frenchmen --which a German might forgive; but Kant, said Heine, had killed God, had undermined the most precious arguments of theology. "What a sharp contrast between the outer life of this man, and his destructive, world-convulsing thoughts! Had the citizens of Königsberg surmised the whole significance of those thoughts, they would have felt a more profound awe in the presence of this man than in that of an executioner, who merely slays human beings. But the good people saw in him nothing but a professor of philosophy; and when at the fixed hour he sauntered by, they nodded a friendly greeting, and set their watches."
Was this caricature, or revelation?
Critique of Pure Reason
Theory of perception
Kant defines his theory of perception in his influential work the “Critique of Pure Reason". …. Kant maintains that our understanding of the external world had its foundations not merely in experience, but in both experience and a priori concepts. ….
Firstly, Kant distinguishes between analytic and synthetic propositions:
1. Analytic proposition: a proposition whose predicate concept is contained in its subject concept; e.g., "All bachelors are unmarried," or, "All bodies take up space."
2. Synthetic proposition: a proposition whose predicate concept is not contained in its subject concept; e.g., "All bachelors are alone," or, "All bodies have weight."
An analytic proposition is true by nature of the meaning of the words in the sentence — we require no further knowledge than a grasp of the language to understand this proposition. On the other hand, a synthetic statement is one that tells us something about the world. The truth or falsehood of synthetic statements derives from something outside their linguistic content.
Before Kant's first Critique, empiricists (cf. Hume) and rationalists (cf. Leibniz) assumed that all synthetic statements required experience to be known.
Kant, however, contests this: he claims that elementary mathematics, like arithmetic, is synthetic a priori, in that its statements provide new knowledge, but knowledge that is not derived from experience. This becomes part of his over-all argument for transcendental idealism. That is, he argues that the possibility of experience depends on certain necessary conditions — which he calls a priori forms — and that these conditions structure and hold true of the world of experience. In so doing, his main claims in the "Transcendental Aesthetic" are that mathematic judgments are synthetic a priori and in addition, that Space and Time are not derived from experience but rather are its preconditions.
Once we have grasped the functions of basic arithmetic, we do not need any empirical experience to know that 100 + 100 = 200, and so it appears that arithmetic is analytic. However, that it is analytic can be disproved by considering the calculation 5 + 7 = 12: there is nothing in the numbers 5 and 7 by which the number 12 can be inferred. Thus "5 + 7" and "the cube root of 1,728" or "12" are not analytic because their reference is the same but their sense is not — the mathematical judgment "5 + 7 = 12" tells us something new about the world. It is self-evident, and undeniably a priori, but at the same time it is synthetic. Thus Kant proved that a proposition can be synthetic and known a priori.
Kant asserts that experience is based both on the perception of external objects and a priori knowledge. The external world, he writes, provides those things that we sense. But it is our mind that processes this information and gives it order, allowing us to comprehend it.
[First, our mind supplies the concepts of space and time to keep the (intuitive) sensed objects in order. Then, according to the "transcendental unity of apperception", our mind supplies the concepts of categoreal understanding which raise the perceived objects and events into the "conceptual" knowledge of relationships, sequences, and laws.] Without the concepts, perceptions are nondescript; without the perceptions, concepts are meaningless — thus the famous statement, "Thoughts without content are empty, intuitions [sensibility] without concepts are blind."
Kant also claims that an external environment is necessary for the establishment of the self. Although Kant would want to argue that there is no empirical way of observing the self, we can see the logical necessity of the self when we observe that we can have different perceptions of the external environment over time. By uniting all of these general representations into one global representation, we can see how a transcendental self emerges. "I am therefore conscious of the identical self in regard to the manifold of the representations that are given to me in an intuition because I call them all together my representations."
Categories of the Faculty of Understanding
Kant deemed it obvious that we have some objective knowledge of the world, such as, say, Newtonian physics. But this knowledge relies on synthetic, a priori laws of nature, like causality and substance. The problem, then, is how this is possible. Kant's solution was to reason that the subject must supply laws that make experience of objects possible, and that these laws are the synthetic, a priori laws of nature that we know apply to all objects before we experience them. So, to deduce all these laws, Kant examined experience in general, dissecting in it what is supplied by the mind from what is supplied by the given intuitions. What has just been explicated is commonly called a transcendental deduction.
To begin with, Kant's distinction between the a posteriori being contingent and particular knowledge, and the a priori being universal and necessary knowledge, must be kept in mind. For if we merely connect two intuitions together in a perceiving subject, the knowledge is always subjective because it is derived a posteriori, when what is desired is for the knowledge to be objective, that is, for the two intuitions to refer to the object and hold good of it necessarily universally for anyone at any time, not just the perceiving subject in its current condition. What else is equivalent to objective knowledge besides the a priori, that is to say, universal and necessary knowledge? Nothing else, and hence before knowledge can be objective, it must be incorporated under an a priori category of the understanding.
For example, say a subject says, "The sun shines on the stone; the stone grows warm," which is all he perceives in perception. His judgment is contingent and holds no necessity. But if he says, "The sunshine causes the stone to warm," he subsumes the perception under the category of causality, which is not found in the perception, and necessarily synthesizes the concept sunshine with the concept heat, producing a necessarily universally true judgment.
To explain the categories in more detail, they are the preconditions of the construction of objects in the mind. Indeed, to even think of the sun and stone presupposes the category of subsistence, that is, substance. For the categories synthesize the random data of the sensory manifold into intelligible objects. …… Hence, one can have an a priori cognition of the totality of all objects of experience. …..
Judgments are, for Kant, the preconditions of any thought. Man thinks via judgments, so all possible judgments must be listed and the perceptions connected within them put aside, so as to make it possible to examine the moments when the understanding is engaged in constructing judgments. For the categories are equivalent to these moments, in that they are concepts of [understanding] in general, so far as they are determined by these moments universally and necessarily. Thus by listing all the moments, one can deduce from them all of the categories.
One may now ask: How many possible judgments are there? Kant believed that all the possible propositions within Aristotle's syllogistic logic are equivalent to all possible judgments, and that all the logical operators within the propositions are equivalent to the moments of the understanding within judgments. Thus he listed Aristotle's system in four groups of three: quantity (universal, particular, singular), quality (affirmative, negative, infinite), relation (categorical, hypothetical, disjunctive) and modality (problematic, assertoric, apodeictic). The parallelism with Kant's categories is obvious: quantity (unity, plurality, totality), quality (reality, negation, limitation), relation (substance, cause, community) and modality (possibility, existence, necessity).
The fundamental building blocks of experience, i.e. objective knowledge, are now in place. First there is the sensibility, which supplies the mind with intuitions, and then there is the understanding, which produces judgments of these intuitions and can subsume them under categories. These categories lift the intuitions up out of the subject's current state of consciousness and place them within consciousness in general, producing universally necessary knowledge. For the categories are innate in any rational being, so any intuition thought within a category in one mind is necessarily subsumed and understood identically in any mind. In other words, we filter what we see and hear.
Before Kant, it was generally held that truths of reason must be analytic, meaning that what is stated in the predicate must already be present in the subject…… It was thought that all truths of reason, or necessary truths, are of this kind.
David Hume (1711–1776) at first accepted the general view of rationalism about a priori knowledge. However, upon closer examination of the subject, Hume discovered that some judgments thought to be analytic, especially those related to cause and effect, were actually synthetic (i.e., no analysis of the subject will reveal the predicate). They thus depend exclusively upon experience and are therefore a posteriori.
Before Hume, rationalists had held that effect could be deduced from cause; Hume argued that it could not and from this inferred that nothing at all could be known a priori in relation to cause and effect. Kant (1724–1804), who was brought up under the auspices of rationalism, was deeply disturbed by Hume's skepticism. "Kant tells us that David Hume awakened him from his dogmatic slumbers."
Kant decided to find an answer and spent at least twelve years thinking about the subject. Kant's work was stimulated by his decision to take seriously Hume's skeptical conclusions about such basic principles as cause and effect. In Kant's view, Hume's skepticism rested on the premise that all ideas are presentations of sensory experience. The problem that Hume identified was that basic principles such as causality cannot be derived from sense experience only: experience shows only that one event regularly succeeds another, not that it is caused by it.
In section VI ("The General Problem of Pure Reason") of the introduction to the Critique of Pure Reason, Kant explains that Hume stopped short of considering that a synthetic judgment could be made 'a priori'. Kant's goal was to find some way to derive cause and effect without relying on empirical knowledge. Kant rejects analytical methods for this, arguing that analytic reasoning cannot tell us anything that is not already self-evident, so his goal was to find a way to demonstrate how the synthetic a priori is possible.
Conclusion: Prior to Kant, it was thought that all a priori knowledge must be analytic. Kant, however, argues that our knowledge of mathematics, of the first principles of natural science, and of metaphysics, is both a priori and synthetic. So his goal was to find a way to demonstrate how the synthetic a priori is possible.
Synthetic a priori judgments
Kant argues that there are synthetic judgments such as the connection of cause and effect (e.g., "Every effect has a cause.") where no analysis of the subject will produce the predicate. Kant reasons that statements such as those found in geometry and Newtonian physics are synthetic judgments. Kant uses the classical example of 7 + 5 = 12. No amount of analysis will find 12 in either 7 or 5. Thus Kant arrives at the conclusion that all pure mathematics is synthetic though a priori; the number 7 is seven and the number 5 is five and the number 12 is twelve and the same principle applies to other numerals; in other words, they are universal and necessary. For Kant then, mathematics is synthetic judgment a priori.
Conventional reasoning would have regarded such an equation to be analytic a priori by considering both 7 and 5 to be part of one subject being analyzed, however Kant looked upon 7 and 5 as two separate values, with the value of five being applied to that of 7 and synthetically arriving at the logical conclusion that they equal 12.
This conclusion led Kant …. to inquire whether it could be possible to ground synthetic a priori knowledge for a study of metaphysics, because most of the principles of metaphysics from Plato through to Kant's immediate predecessors made assertions about the world or about God or about the soul that were not self-evident but which could not be derived from empirical observation.
For Kant, all post-Cartesian metaphysics is mistaken from its very beginning: the empiricists are mistaken because they assert that it is not possible to go beyond experience and the dogmatists are mistaken because they assert that it is possible to go beyond experience through theoretical reason.
Therefore, Kant proposes a new basis for a science of metaphysics, posing the question: how is a science of metaphysics possible, if at all? According to Kant, only practical reason, the faculty of moral consciousness, the moral law of which everyone is immediately aware, makes it possible to know things as they are. [Charles George Herbermann; et al. (eds.). The Catholic encyclopedia 10. p. 232] This led to his most influential contribution to metaphysics: the abandonment of the quest to try to know the world as it is "in itself" independent of sense experience.
He demonstrated this with a thought experiment, showing that it is not possible to meaningfully conceive of an object that exists outside of time and has no spatial components and is not structured in accordance with the categories of the understanding (Verstand), such as substance and causality. Although such an object cannot be conceived, Kant argues, there is no way of showing that such an object does not exist. Therefore, Kant says, the science of metaphysics must not attempt to reach beyond the limits of possible experience but must discuss only those limits, thus furthering the understanding of ourselves as thinking beings.
The human mind is incapable of going beyond experience so as to obtain a knowledge of ultimate reality, because no direct advance can be made from pure ideas to objective existence. [Watson, John (1908). The philosophy of Kant explained. J. Maclehose. pp. 62–72]
Kant writes, "Since, then, the receptivity of the subject, its capacity to be affected by objects, must necessarily precede all intuitions of these objects, it can readily be understood how the form of all appearances can be given prior to all actual perceptions, and so exist in the mind a priori" (A26/B42).
Appearance is then, via the faculty of transcendental imagination (Einbildungskraft), grounded systematically in accordance with the categories of the understanding. Kant's metaphysical system, which focuses on the operations of cognitive faculties (Erkenntnisvermögen), places substantial limits on knowledge not founded in the forms of sensibility (Sinnlichkeit).
Thus it sees the error of metaphysical systems prior to the Critique as failing to first take into consideration the limitations of the human capacity for knowledge. According to Heidegger, transcendental imagination is what Kant also refers to as the unknown common root uniting sense and understanding, the two component parts of experience. Transcendental imagination is described in the first edition of the Critique of Pure Reason but Kant omits it from the second edition of 1787.
It is because he takes into account the role of people's cognitive faculties in structuring the known and knowable world that in the second preface to the Critique of Pure Reason Kant compares his critical philosophy to Copernicus' revolution in astronomy. Kant writes: "Hitherto it has been assumed that all our knowledge must conform to objects. But all attempts to extend our knowledge of objects by establishing something in regard to them a priori, by means of concepts, have, on this assumption, ended in failure. We must therefore make trial whether we may not have more success in the tasks of metaphysics, if we suppose that objects must conform to our knowledge". Just as Copernicus revolutionized astronomy by taking the position of the observer into account, Kant's critical philosophy takes into account the position of the knower of the world in general and reveals its impact on the structure of the known world. Kant's view is that in explaining the movement of celestial bodies Copernicus rejected the idea that the movement is in the stars and accepted it as a part of the spectator. Knowledge does not depend so much on the object of knowledge as on the capacity of the knower.
Kant's transcendental idealism should be distinguished from idealistic systems such as that of George Berkeley. While Kant claimed that phenomena depend upon the conditions of sensibility, space and time, and on the synthesizing activity of the mind manifested in the rule-based structuring of perceptions into a world of objects, this thesis is not equivalent to mind-dependence in the sense of Berkeley's idealism. Kant defines transcendental idealism:
“I understand by the transcendental idealism of all appearances the doctrine that they are all together to be regarded as mere representations and not things in themselves, and accordingly that time and space are only sensible forms of our intuition (Anschauung), but not determinations given for themselves or conditions of objects as things in themselves. To this idealism is opposed transcendental realism, which regards space and time as something given in themselves (independent of our sensibility).” — (CPR, A369)
Kant's project in the Critique of Pure Reason
The main topic of the Critique of Pure Reason is the possibility of metaphysics, understood in a specific way. Kant defines metaphysics in terms of “the cognitions after which reason might strive independently of all experience,” and his goal in the book is to reach a “decision about the possibility or impossibility of a metaphysics in general, and the determination of its sources, as well as its extent and boundaries, all, however, from principles”. Thus metaphysics for Kant concerns a priori knowledge, or knowledge whose justification does not depend on experience; and he associates a priori knowledge with reason. The project of the Critique is to examine whether, how, and to what extent human reason is capable of a priori knowledge.
The Critique of Pure Reason
The simplest way of describing the contents of the Critique is to say that it is a treatise about metaphysics: it seeks to show the impossibility of one sort of metaphysics and to lay the foundations for another.
The Leibnizian metaphysics, the object of Kant’s attack, is criticized for assuming that the human mind can arrive by pure thought at truths about entities which, by their very nature, can never be objects of experience, such as God, freedom, and immortality. Kant maintained, however, that the mind has no such power and that the vaunted metaphysics is thus a sham.
As Kant saw it, the problem of metaphysics, as indeed of any science, is to explain how, on the one hand, its principles can be necessary and universal and yet, on the other hand, involve also a knowledge of the real and so provide the investigator with the possibility of more knowledge than is analytically contained in what he already knows. To meet these two conditions, Kant maintained, knowledge must rest on judgments that are a priori, for it is only as they are separate from the contingencies of experience that they could be necessary and yet also synthetic—i.e., so that the predicate term contains something more than is analytically contained in the subject. ….. Hence, the basic problem, as Kant formulated it, is to determine “How [i.e., under what conditions] are synthetic a priori judgments possible?”
This problem arises, according to Kant, in three fields—mathematics, physics, and metaphysics—and the three main divisions of the first part of the Critique deal respectively with these.
In the Transcendental Aesthetic, Kant argued that mathematics necessarily deals with space and time and then claimed that these are both a priori forms of human sensibility that condition whatever is apprehended through the senses.
In the Transcendental Analytic,…. he maintained that physics is a priori and synthetic because in its ordering of experience it uses concepts of a special sort. These concepts—“categories,” he called them—are not so much read out of experience as read into it and, hence, are a priori, or pure, as opposed to empirical. But they differ from empirical concepts in something more than their origin: their whole role in knowledge is different. For, whereas empirical concepts serve to correlate particular experiences and so to bring out in a detailed way how experience is ordered, the categories have the function of prescribing the general form that this detailed order must take. They belong, as it were, to the very framework of knowledge. But although they are indispensable for objective knowledge, the sole knowledge that the categories can yield is of objects of possible experience; they yield valid and real knowledge only when they are ordering what is given through sense in space and time.
In the Transcendental Dialectic Kant turned to consideration of a priori synthetic judgments in metaphysics. Here, he claimed, the situation is just the reverse from what it is in mathematics and physics. Metaphysics cuts itself off from sense experience in attempting to go beyond it and, for this very reason, fails to attain a single true a priori synthetic judgment. To justify this claim, Kant analyzed the use that metaphysics makes of the concept of the unconditioned. Reason, according to Kant, seeks for the unconditioned or absolute in three distinct spheres: (1) in philosophical psychology, it seeks for an absolute subject of knowledge; (2) in the sphere of cosmology, it seeks for an absolute beginning of things in time, for an absolute limit to them in space, and for an absolute limit to their divisibility; and (3) in the sphere of theology, it seeks for an absolute condition for all things. In each case, Kant claimed to show that the attempt is doomed to failure by leading to an antinomy in which equally good reasons can be given for both the affirmative and the negative position. The metaphysical “sciences” of rational psychology, rational cosmology, and natural theology, familiar to Kant from the text of Baumgarten, on which he had to comment in his lectures, thus turn out to be without foundation.