Notes on <Kant and the Critique of Pure Reason> - The conceptual conditions of objects (The Analytic)

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The argument of the Analytic: questions of method

Although the Aesthetic provides an account of how objects are intuited, it does not establish their givenness in a cognitive sense. It is the job of the Analytic to show, through an account of the faculty of understanding, how objects of intuition, and space and time themselves, become objects of thought, and thus how empirical knowledge is possible.

There are different readings of Analytic: progressive and regressive. Strawson’s view is that Kant is attempting to prove the necessity of an objective empirical world from premises to which the skeptic himself is committed; Kant is interpreted as seeking to demonstrate that skepticism is self-refuting(progressive interpretation, “only if”/necessary conditions). At the other extreme, the Analytic may be interpreted much more modestly, as a theory merely designed to explain why our experience has the conceptual character that it seems to have: its starting point is phenomenological - the world as we find it - and the argument for its truth is that it accounts for the appearances(regressive interpretation, “if”/sufficient conditions).

A way of reading the Analytic

  1. Assuming Transcendental Idealism We may interpret Analytic as premised on the truth of transcendental idealism. Kant argues that conceptual form is shaped by sensible form, and that the a priori sensible and conceptual features of objects are related as content and form, rather than comprising discrete sets of properties of objects.

Kant’s proof of the principle of causality, for example, can now be read as having to show, not that there is something wrong with the supposition that things in reality are not causally ordered, or that if they are then we cannot know this, but that the principle of causality performs some transcendental function, i.e. that it has the same sort of object-enabling status as the Aesthetic showed the forms of intuition to possess. The key to the Analytic, on this account, consists in the identification of a general transcendental function for concepts to perform, and the success of any given proof will depend upon its demonstrating a relation of fit between this function, and a given component of the commonsense metaphysics of experience.

If causality is a concept that we use, not because our experience has a certain character, but because it makes objects of a certain (transcendentally specified) sort possible for us, then it has necessity for us.

Interpreting the Analytic as an attempt to reconstruct empirical knowledge on a transcendental idealist basis also narrows the difference between the progressive and regressive readings of the Analytic, and allows it to be seen how Kant may in a sense be pursuing both strategies at the same time.

What we should expect to find in the Analytic, then, is an account of the general transcendental function of conceptualization, and an account of which particular concepts perform this function for us and how they do so. The first is contained in the Transcendental Deduction, the second in the Analytic of Principles.

The relation of thought to objects: the apriority of conceptual form(Idea of a Transcendental Logic)

Transcendental logic is concerned with the relation of thought to objects as given in space and time.

Synthetic unity

If “the combination of a manifold” can never come to us through the senses, then it must be a priori. We are, then, entitled to claim that there must be at least one a priori concept, namely unity. “Synthetic unity” is the most minimal form that we must discover in experience in order for it to have cognitive significance.

The problem of connecting the sensible and the conceptual

The consequence of the commitment of apriority of conceptual form and rejection of empiricism is the problem that due to the fact that the fundamental concepts necessary for experience are not derived from experience, and yet need to be applied to sensible objects. This creates a possibility which Kant needs to rule out: namely, that there should fail to be any fit between objects as sensed and a priori concepts, between the sensible and conceptual components of the structure of experience.

The problem is: how is the justified application of a priori concepts to objects possible? Kant’s question needs to be answered with reference to the structure and capacities of the subject. The solution is provided in the Transcendental Deduction. And transcendental idealism, just as it gives rise to the problem of connecting the sensible and the conceptual, at the same time supplies the key to its solution. To justify the application of a priori concepts it suffices to show that the subject has cognitive needs which can be fulfilled if its objects have a form determined by those concepts, and how objects can assume that conceptual form. This is what Kant’s theory of apperception, synthesis, schematism and the analogies of experience, is meant to provide.

The elements of thought: the categories(The Clue to the Discovery of all Pure Concepts of the Understanding)

The metaphysical deduction is based on the supposition that the function of judgement provides a ‘clue’ to the pure concepts of the understanding. In judgement one representation is brought into relation with another in such a way as to yield a unity. And there are 12 forms of judgments, divided into 4 groups(quantity, quality, relation, modality), each containing 3 moments.

The pure concepts which give rise to unity in both judgements and intuitions are the pure concepts of understanding, which are listed in the table of Categories.

The shortcomings of the metaphysical deduction

Kant’s intention offering the derivations of categories is unclear. One interpretation is that Kant is taking categories for granted, which is similar to Metaphysical Exposition in Aesthetic, where Kant takes space and time as granted. Another interpretation, Kant means to prove these categories are necessary for any subject with discursive intellect. Probably the latter is what Kant means. Kant’s derivation needs to be located in the context of transcendental logic, he claims that if one looks for concepts that satisfy the conditions of being both associated with concepts of formal logic and capable of playing a role in organizing intuition, then one arrives at the twelve categories. There are objections to the categorization of table of judgments, correspondence between table of judgment and table of categories and the table of categories.

However, what is most important in the metaphysical deduction is the suggestion, which is pursued in the Transcendental Deduction, that if there were not a conceptual form shared by thought and intuition, neither would be possible.

The preconditions and source of conceptual form: the subject-object relation (The Transcendental Deduction)

The Transcendental Deduction is the heart of the Analytic.

A synopsis of the text of the Deduction

Section 13

How the a priori concepts can relate to objects which they yet do not obtain from any experience, the explanation of which is called Transcendental Deduction.

The objective validity for concepts of space and time have already been proven, since only by pure forms of sensibility can objects appear to us. Space and time are pure intuitions which contain a priori the condition of the possibility of objects as appearances, and the synthesis which takes place in them has objective validity.

However, the questions is for categories of understanding, that is, how subjective conditions of thought can have objective validity, for appearances can certainly be given in intuition independently of functions of the understanding. For example, how to establish the objective validity for causality? In experience, all we have is constant conjunctions of events(as Hume said), and there is no object among appearances corresponding to causality.

Section 14

Solution to the above problem is that a priori concepts serve as the necessary conditions for object to be known to us. The objective validity of the categories as a priori concepts rests on the fact that so far as the form of thought is concerned, through them alone does experience become possible.

A priori concepts are justified, if they are “contained in the concept of possible experience”, i.e. they are transcendental conditions. If we can prove by their means alone an object can be thought, this will be a sufficient deduction of them, and will justify their objective validity.

A Deduction

The A Deduction is expressed in the language of cognitive powers and their operations. Kant sets out the argument twice, dividing the A Deduction into a “preparatory” (A98-114) and a “systematic” exposition (A115-30). In both cognition is conceived as requiring a multi-layered set of synthetic operations attributed to different cognitive powers: receptivity of sensibility, combination of the data of sense by the imagination, and finally conceptual operations on the part of the understanding. With each upward shift of level, a new kind of unity is created, the higher levels presupposing the lower, and the highest unity, that of the understanding, is held to be sufficient for the unity of self-consciousness.

B Deduction

The B Deduction differs most markedly through its contraction of the synthesis story. The concept of synthesis itself remains vital, but Kant does not highlight the detailed operations of synthesizing faculties.

A deduction, or subjective deduction focuses on the “subjective sources which form the a priori foundation of the possibility of experience”. An “objective deduction”, by contrast, would spell out the transcendental conditions of experience without reference to the subject’s cognitive powers. Their position is not truly equal, however, for Kant regards the subjective deduction as strictly inessential. The B Deduction is an objective deduction.

Here too there is a textual division into two halves, but it has a different basis: they comprise two steps in a single proof. The first half comprehends §15-20 and §21-26 comprises the second half of the B Deduction. The B Deduction, like its predecessor, ends with an account of why transcendental idealism is required for the justification of the categories(§27).

Interpretations of the Deduction

The dominant line of interpretation finds in the Deduction a progressive, anti-skeptical argument, from the incontrovertible premise that we have experience or are self-conscious, to the strong conclusion that we have experience of an objective world. The minority view is that the Deduction is concerned with the conditions of empirical knowledge, not those of self consciousness: its argument is regressive, and effective against empiricism but not skepticism.

Deduction should not be interpreted as seeking to extract a refutation of skepticism from the concept of experience or any other basic concept. Nor does it merely identify the presuppositions of empirical knowledge by showing that a posteriori, empirical knowledge claims rest on a priori conditions. Rather, it attempts to show that a priori concepts have justified application to objects, through showing that they perform a transcendental function, and on the basis that the objects to which they are applied are transcendentally ideal.

A theory of the subject-object relation

Deduction supplies a theory of how the elements of subject, object and relation which allows object to be taken as such by the subject maybe conceived.

The transcendental unity of apperception

The first element in this structure to be examined is the subject. In the Aesthetic, Kant asserted that the self is known only as appearance: through inner sense I cognize myself in terms of temporal, empirical objects. However, the self is not, and cannot be given empirically, there must be a priori self-consciousness, transcendental unity of apperception, a “pure original unchangeable consciousness” of self. In B Deduction, Kant describes the requirement of transcendental apperception as:

It must be possible for the ‘I think’ to accompany all my representations; for otherwise something would be represented in me which could not be thought at all, and that is equivalent to saying that the representation would be impossible, or at least would be nothing to me.

Kant’s claim is that each of my representations must be such that it is possible for me to recognize it as mine in an act of reflection. For the satisfaction of this condition, the representation “I”, an invariant, a priori representation free from empirical content, is essential; “otherwise I should have as many-colored and diverse a self as I have representations of which I am conscious”.

What is the transcendental unity of apperception? At one level, Kant’s answer is clear: transcendental apperception consists in a merely formal unity that does not amount to knowledge of any object. The formal unity in question is just that unity of representations.

Another way of is to suppose that he does mean the “I” to be understood as referring to a thing in itself. His position would then be that the self, qua the world of appearances, is just a unity of representations, but that, in transcendent terms, it is a thing in itself. But it cannot be right, for it conflicts with the original claim in the Aesthetic, reiterated in the Deduction at B157-9, that the self is known only as appearance.

So Kant’s position is that, though the unity of apperception guarantees the numerical identity of something, we cannot know what it is. The reference of the ‘I’ is undecidable, because our consciousness of the existing ‘something’ cannot be put together with the formal unity of apperception to yield knowledge of an ‘I’-identical thing. It may be that the existing something is a thing in itself, which I cannot have knowledge of, or it could also be that the ‘something’ underlying apperception may be without ‘I’. Then all that is determined through apperception exists solely within the sphere of representation, something which we can conceive only as the thinking subject which is a condition of possibility of experience. For Kant, ‘I’ refers to something over and above my representations, but we cannot know if it is to the subject of representation or a thing in itself.

The transcendental object

The second element in the pre-categorial structure of experience to be explicated is the side of the object, the fundamental notion that our representations are of things. Experience of objects is possible only through the concept of an object.

The corresponding notion of object is not that of something external to the mind, let alone a substance, but simply the correlate of a judgement, that to which a concept is applied, a judgemental object.

The role of transcendental object is to provide a point to which the elements of the manifold of intuition may be referred, allowing appearances to be determined as thinkable objects of intuition. In order to play this role, it is essential that the transcendental object should not ‘itself be intuited by us’. It needs to be excluded from the manifold of intuition if an infinite regress is to be avoided - which is why its concept cannot be any richer than that of an ‘x’ which ‘is nothing to us’, and of which all that can be said is that it ‘has to be distinct from our representations’ (A105).

The transcendental object maps directly onto the concept of synthetic unity with which Kant attacks empiricism. What it adds is a connection with objectivity: the transcendental object is what confers ‘objective reality’ on our representations(A109).

The envisaged role of the concept of transcendental object in the construction of experience is clear: by unifying our representations, it allows intuition to yield objects of thought. Statements at later point of Critique strongly suggest an identification of the transcendental object with the thing in itself, a thing that is transcendentally real. If this is Kant’s position, his transcendental idealism disintegrates, for it implies that we do know things in themselves after all.

The interpretation of transcendental object that avoids identification with thing in itself and also makes sense for Kant’s further statements is: The concept of the transcendental object as ‘a something = x’ contains no reference to a constitution, the concept of the transcendental object therefore stands in need of concretization or realization - ‘determination’.

The concepts of thing in itself and transcendental object should therefore not be confused. They are the same in respect of both being completely blank, and the transcendental object is the sole representation by means of which we can think of things in themselves; but it is the transcendental object, not the thing in itself, which is the source of the unity of objects, and each is unknowable for quite different reasons: the thing in itself is unknowable because it has a constitution inaccessible to our mode of cognition, the transcendental object because it is, as the concept of an object prior to any constitution, not an entity at all.

Although to the question, what is the constitution of a transcendental object, no answer can be given stating what it is, we can yet reply that the question itself is nothing, because there is no given object to it. No further question of identity remains once it has been explained how the concept functions in the constitution of experience, and that its ontologically superior realization is necessarily inaccessible to us.

Kant says that an object is ‘that in the concept of which the manifold of a given intuition is united’ (B137), not that an object is, or that the concept of an object is that of, a unified manifold.

The concept of the transcendental object may consequently be regarded as expressing the irreducibility of the concept of an object, as well as its a priority - just as the ‘I’ of apperception expresses the irreducibility of subjectivity and is not to be reduced to relations between representations. Exactly paralleling the transcendental unity of apperception, it sits on the borderline between the inside and outside of experience.

Subject and object as making one another possible

Granted that the transcendental unity of apperception and transcendental object are necessary for experience, what makes them possible? Kant’s master stroke in the Deduction is to propose that each explains the other.

First the subject makes the object possible. The relation of representation to object is constituted by the necessary unity of representations, and this unity is in turn identical with the necessary unity of consciousness. “The unity which the object makes necessary can be nothing else than the formal unity of consciousness.” But it also means that the unity of objects derives from the unity of consciousness, that the latter is the ground of the former. “It is the unity of consciousness that alone constitutes the relation of representations to an object”. The production of synthetic unity is thus revealed to be identical with cognition of objects: “when we have thus produced synthetic unity in the manifold of intuition … we are in a position to say that we know the object”.

Second the object makes the subject possible, again through a priori synthesis. “The mind could never think its identity in the manifold of its representations… if it did not have before its eyes the identity of the act, whereby it subordinates all synthesis of apprehension… to a transcendental unity, thereby rendering possible their interconnection”(A108).

What needs to be explained is how we can prise ourselves as subjects apart from our representations to achieve self-consciousness. Kan proposes, a priori conceptual activity. Self-consciousness is consciousness of spontaneity, so it must involve representation of oneself in terms of activity, and this activity needs to be conceptual, or it would not make the “I” thinkable, and it must be based on a priori conditions, or it would be empirical.

The existence of this consciousness is testified by our representation of ourselves as spontaneous, which is a condition of our representing ourselves as thinkers of thoughts and makers of judgements. Kant’s argument, in sum, is that consciousness of a priori synthesis explains transcendental apperception, and that nothing else can be conceived to do so, and since this synthesis implies the representation of synthetic unities, self-consciousness presupposes consciousness of objects; unless we took our representations as having a reference beyond themselves to objects, consciousness of self identity would not be possible.

By showing the dependence of transcendental apperception on a priori synthesis, the Deduction establishes the necessity of there being objects corresponding to and distinct from our representations.

The result is a picture of self and nature as mirroring one another, and a re-conception of self consciousness.

The legitimation of the categories

Finally Kant’s theory of subject-object relation realizes the legitimation of the categories: a priori synthesis is necessarily synthesis in accordance with rules derived from the categories.

There are several arguments for this. One rests on familiar Kantian doctrines: synthesis is an act and activity is a feature of the understanding, the understanding is a source of a priori concepts, the categories, so a priori synthesis must be synthesis according to the categories. Second is: transcendental apperception is possible only if there is a priori conceptual synthesis, and this is possible only if there are a priori concepts, i.e. categories. Third argument: the transcendental object is the concept of a something in general, and the categories are concepts of objects in general, so synthesis dictated by the transcendental object is necessarily in accordance with the categories.

By the end of the Deduction, the basic problem of the Analytic has been solved. The task was to show that a priori concepts function as transcendental conditions. In order to do this, a transcendental function for conceptuality needed to be discovered, and the transcendental unity of apperception has supplied this: it is what necessitates that there be objects, and that they have a priori conceptual form.

There remained the task of securing for objects a positively subject-agreeing constitution: it is one thing to show that appearances cannot have a constitution discrepant with the conceptual powers of the subject, and another to show that their sensible constitution must conform to our conceptual powers. The question is how one and the same object can figure in relation to both sensibility and understanding - why are there not two worlds of objects, one for each faculty?

The theory of a priori synthesis, which entails that appearances are intrinsically fitted to receive the categories, provides Kant’s solution: it shows that the given is conceptually constituted. The Deduction shows that the empiricist idea of two stages in cognition or levels of consciousness - a level of experiential data given independently of thought, and a level of thought directed at that data - is incoherent. The job of getting consciousness to transcend itself towards the world, on Kant’s account, is already performed at the level of the given, which is such that thought based immediately on it is necessarily directed at objects presented in it. The internal tie between experience and concepts precludes the possibility that concept application rests fundamentally on inference.

The Deduction has, then, worked out the idea advanced in the metaphysical deduction, that there must be a structure common to thought and intuition: the “same function that gives unity to the various representations in a judgement also gives unity to the mere synthesis of various representations in an intuition” (B104-5).

The specific conceptual form of human experience: causally interacting substances (The Schematism, The Analogies, The Refutation of Idealism)

The section which is crucial for the Critique’s legitimation of the metaphysics of experience is the Analogies of Experience (supplemented by the Refutation of Idealism). Here Kant argues that the objectivity which the Deduction has shown to be necessary must, for subjects of spatio-temporal intuition, assume a particular form, namely that of a world of causally interacting substances.

The Schematism

Here Kant returns to the question of how the sensible and the conceptual are related. Whenever an object is subsumed under a concept, the representation of the object must be, Kant says ‘homogeneous with the concept’. In order for a concept to get a grip on an object given in intuition, there must be something in the concept which is capable of being represented in intuition - concepts must be such that it is possible for intuitions to conform to them. But the categories are quite heterogeneous to sensible intuition.

The solution, Kant suggests, is to assume ‘some third thing’, which is homogeneous with both the categories and intuition or appearance. This ‘mediating representation’ must be in one respect intellectual, and in another sensible. Kant calls it a schema.

A transcendental schema consists in a transcendental determination of time. For example, concept of substance when schematized becomes “permanence of the real in time”, concept of causality becomes: “the real upon which, whenever posited, something else always follows”.

The obscurity attaching to the doctrine of schematism is the price which Kant ultimately pays for escaping from rationalism and empiricism, and rejecting the transcendental realist model of concept application.

The Analogies of Experience

The Analogies proceed to show that the schematized categories of substance and causality perform a transcendental function.

Our temporality gives rise, in the context of the transcendental theory of experience, to a problem concerning temporal judgement, namely: how is it possible for us to represent objects as being in time, in a sense which transcends the temporality of our representations?

Substance is dealt with in the first analogy, and causality in the second; the third analogy assembles their results, and puts space into the picture. The three analogies correspond to the relational categories (subsistence, causality, community) and modes of time (duration, succession, simultaneity.

The first analogy

The first analogy aims to establish the principle of permanence of substance: “In all change of appearances substance is permanent”. All appearances contain the permanent (substance) as the object itself, and the transitory as its mere determination, that is, as a way the object exists’ (A182).

The second analogy

The second analogy is less straightforward. It aims to establish the principle of causality: ‘all alterations take place in conformity with the law of connection of cause and effect’ (B232). i.e. every event must have a cause.

The argument, briefly stated, is that experience of objective change, i.e. of the world as changing, as opposed to merely oneself or one’s representations changing, is necessary for experience of an objective time-order, and that the distinction between change occurring in our representations, and change occurring in an objective world, can be made only by employing the concept of causality.

The relation of cause and effect is both necessary and irreversible. The principle of causality is justified, therefore, on the grounds that only an a priori rule, by virtue of which one appearance can be regarded as necessitating another, allows us to refer change to objects, as required for an objective time-order.

The third analogy

The third analogy extends the second analogy’s claim that causality is required for objectivity. Its principle is that of coexistence: ‘All substances, in so far as they can be perceived to coexist in space, are in thoroughgoing reciprocity’ (B256).

Whereas the second analogy was concerned with causality in the form of relations between events, the third is concerned with causality in the form of causal interaction between substances.

Evaluating the Analogies

The idea underlying the analogies is that experience must, on two counts, form a unity: it must conform to the unity of apperception, and in order to do this, it must conform to the unity of time.

Kant is generally acclaimed as having articulated something extremely important about objectivity in the Analogies, but standardly criticized as having inflated his conclusions. What Kant shows is that in order to make objective judgements, we need some way of organizing our experience which goes beyond what is sensorily given. But this condition does not demand as much as Kant claims. Consequently Kant does not rule out Humean constant conjunction as an analysis of causality. However, Kant’s question concerns the initial conceptual form of the given, not inferences about reality that may be made on the basis of it.

The objects to first and second analogy of relative permanence and constant conjunction are not appropriate to this transcendental function because relative permanence does not make an objective time-order thinkable and relative permanence is only possible after an objective world has been constituted. Constant conjunction does not specify an a priori conceptual form that intuition can take, it merely imposes constraint on the content of experience. Kant’s claims about absolute permanence and necessary connection are thus not metaphysically ambitious - they appear to be so only in an empiricist light.

Kant may agree with his critics, therefore, that the analogies’ account of the conditions of possibility of objectivity does not bear on the questions they have in mind, and point out that this is irrelevant to what he is arguing. To challenge the conclusions of the analogies, it would need to be shown either that they fail to cohere with the transcendental theory of experience, or that something else in this theory besides substance and causality could play the same role.

The Refutation of Idealism

Here Kant aims to prove that we have experience of outer objects - objects distinct from us in space - and thus to refute skepticism about the external world. Kant’s objective in the Refutation is to refute material or empirical idealism, and to defend empirical realism.

Kant used the example in the first analogy, that I intuition permanent representations, not representation of a permanent, but the permanent representation is no more necessary than it is sufficient for the representation of a permanent: representations may themselves be transitory yet refer to something permanent.

Kant concludes, empirical consciousness of my existence “is at the same time an immediate consciousness of the existence of other things outside me”. That is, not only must there be things outside me, but I must have consciousness of them, and this consciousness must be immediate, since I would otherwise have to infer the time-order of outer objects, which would require me to identify the time-order of my representations prior to that of their objects - this being, the first analogy has shown, impossible.

Measurement and modality (The Axioms of Intuition, The Anticipations of Perception, The Postulates of Empirical Thought)

These three sections are important for completing Kant’s theory of experience, but marginal to his defense of objectivity.

The Axioms and Anticipations

The Axioms and Anticipations are concerned with ‘mathematical’ principles of pure understanding. These are a priori conceptual conditions for the generation of intuitions. The Axioms are concerned with appearances in quantitative respects, the Anticipations in qualitative. Their respective principles are: ‘All intuitions are extensive magnitudes and In all appearances, the real that is an object of sensation has intensive magnitude, that is, a degree’.

The principle of the Axioms follows from the fact that appearances are intuited as aggregates - manifolds of homogeneous parts - in space and time, and that their representation as wholes presupposes conceptual synthesis.

In the Anticipations Kant indicates that, although the specific quality of any sensation can only be known a posteriori, there is one (and only one) respect in which we can know something a priori about it: we know in advance that any sensation we apprehend (e.g. heat) will allow itself to be represented as having a determinate degree greater than zero on a continuous scale.

The Postulates

In the Postulates Kant analyses the three categories of modality: possibility, actuality and necessity. His general claim is that modal characterizations of objects do not ‘in the least enlarge the concept to which they are attached as predicates’ - rather they ‘express the relation of the concept to the faculty of knowledge’.

Transcendent objects: the concept of noumenon (The Ground of the Distinction of all Objects in general into Phenomena and Noumena)

The Analytic’s account of the conditions under which our thoughts can be known to have objects raises a question: what is to be said about thoughts that fail to meet those conditions, thoughts of objects that we cannot intuit?

In this chapter Kant prepares the way by spelling out in general terms the implications of the Analytic regarding transcendent objects. Kant’s broad intention is to sharpen our appreciation of what is involved in any attempt to think beyond the limits demarcated in the Analytic: before leaving the ‘island’ of empirical knowledge we should, Kant says, cast a glance at the map of the ‘land of truth’ we are about to leave, and ask both ‘by what title we possess even this domain’, and whether we can ‘be satisfied with what it contains’.

The scope of the categories

The conditions of employment of the categories are such that they ‘can never admit of transcendental but always only of empirical employment. the ‘transcendental’ employment of a concept being ‘its application to things in general and in themselves’, i.e. transcendent, and empirical employment being ‘its application merely to appearances’, i.e. immanent (A238-9/B298).

On Kant’s account, the categories are forms of thought or judgement, and concepts of objects in general, not merely concepts and forms of judgement of empirical objects.

for thought the categories are not limited by the conditions of our sensible intuition, but have an unlimited field. It is only the knowledge of that which we think, the determining of the object, that requires intuition.

The distinction of noumena and phenomena

Kant then re-affirms the traditional distinction of sensory and intellectual objects. He introduces two new concepts: noumenon and phenomena.

Noumenon are objects exclusively of understanding, an object given to a subject but only to its intellect or understanding, i.e. not given by sensibility. The concept of an object exclusively of understanding is of course closely related to that of a thing in itself, in so far as a thing in itself is also a thing considered apart from human sensibility. Therefore noumena and the thing in itself, if they refer, refers to the same things, however they are not the same concept. The thing in itself is a bare ontological concept; it is the concept of an object as it is constituted in itself, without reference to our knowledge of it. Noumenon by contrast is an epistemological concept, the concept of an object of a certain mode of cognition, namely intellectual intuition.

Phenomena are objects of sensible intuition. Virtually all that Kant says about phenomena is that they are appearances ‘so far as they are thought as objects according to the unity of the categories’.

Negative and positive senses of noumenon

It is logically possible for noumena to exist, since the concept is not contradictory, the concept of something non-empirical is furthermore forced on us by the recognition that empirical objects are mere appearances. The very concept of appearance points to that of noumenon: because appearance ‘can be nothing by itself’, ‘something which is not in itself appearance must correspond to it’. For these reasons, Kant endorses the division of ‘the world into a world of the senses and a world of the understanding.

Though all of this is true, what must at all costs be appreciated, Kant stresses, is that we cannot in any manner attain knowledge of noumena. The impossibility of our employing the categories transcendentally precludes our determining them as objects for us. And even though we have the concept of intellectual intuition, a concept which is not contradictory, we of course have no knowledge or contentful idea of such a faculty (B308).

The fact that the categories do not arise out of sensibility makes it seems as if they ought to allow us to get hold of objects directly, without sensible mediation (B305). The illusion is related to a fundamental asymmetry between intellect and sensibility: whereas intuition without thought leaves no relation of representation to object, thought without intuition leaves ‘the form of thought’ or categories, which ‘extend further’ than intuition in the sense that they ‘think objects in general, without regard to the special mode (the sensibility) in which they may be given’.

The overall situation can be clarified by distinguish two concepts of noumenon: the negative, indeterminate concept of a thing in so far as it is not an object of sensible intuition, and the positive, determinate concept of a thing in so far as it is an object of non-sensible (thus intellectual) intuition (B307). Thing in itself identifies with the negative sense. The concept in positive sense is problematic, meaning that is a concept forced on us by our reason. Since the possibility of non-sensible intuition can be neither proved nor disproved, the existence of noumena qua objects of intellectual intuition must remain an ‘open question’.

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