Srirupa Datta Choudhury
In this paper, I shall explain Kant’s epistemological position. According to Kant, knowledge is synthetic a priori.  Our knowledge first starts with the reason then proceeds it through understanding and then end with reason. Kant differs from both empiricist and rationalists. For Kant knowledge comes from the joint product of reason and experience. Kant tries to justify the claims of the rationalists by formulating the forms of intuition, that is, space and time and the categories of understanding as a priori. The sensible intuitions are synthesized in the objects of knowledge for Kant. They are brought to the faculty of understanding, which through its categories organize them. Human knowledge as synthetic a priori is possible through the ‘transcendental unity of apperception’. The transcendental unity of apperception provides the highest unity to the sensible intuitions through the categories of understanding. It is the subject of knowledge and provides universality and necessity to the object of knowledge. The knowledge that arises through these processes is synthetic a priori knowledge.

He makes a distinction between analytic knowledge and synthetic a posteriori, a priori knowledge. An ‘analytic’ proposition is one in which the predicate is part of the subject. The judgment “all bodies are extended” is analytic because the idea of extension is already contained in the idea of a body, and the judgment does nothing but analyses our concept of a body. In synthetic judgment the predicate represents a new idea, not already contained in the idea of the subject. For instance- “all bodies are heavy” is synthetic judgment because the idea of weight is no part of the meaning of a body. This judgment does not merely analyze our concept of body, but it gives some extra knowledge of it.

Synthetic proposition are only known through experience. Analytic judgments are universal and necessary and they cannot b derived from experience. On the other hand, synthetic judgments are contingent and probable, because they are derived from experience. Kant says that all analytic judgments are a priori but all a priori judgments are not analytic judgments. It means that some a priori judgments are synthetic and some are analytic. Therefore, Kant says that there are synthetic a priori judgments. The concept of cause would lose universality and necessity, if it is derived from a repeated association of that which happens with that which precedes and from a custom of connecting representations as Hume has done. The concept of cause is universal and necessary precisely because it is not derived from experiences. The concept of cause is a priori knowledge.

In the faculty of a priori concept Kant includes space and time which are regarded by him as the forms of intuitions in which the manifold of sensible intuitions are posited and ordered. Space and time are not derived from sensible intuitions.

Kant holds that the sensations are posited and ordered in a certain form. This form is not derived from the sensible intuition and must therefore be a priori. Kant discuss space and time separately and gives four arguments in favor of the concept of space and five arguments in favor of the concept of time, in order to prove them a priori.

First argument of the concept of space: ‘Space is not an empirical concept, which has been derived from outer experiences.”[1]  By outer experiences, Kant means, “…a property of our mind”,[2] through which, “…we represent to ourselves objects as outside us…”[3] According to Kant, representation is a kind of cognitive process through which objects are regarded as outside us, act on our senses. In order to regard different representations, “…as in different places…,”[4] the representation of space must be presupposed. It appears that the “representation of space cannot, therefore, be empirical obtained from the relations of outer appearance.”[5]

The second argument: “Space is a necessary a priori representation, which underlies all outer intuitions. We can never represent to ourselves the absence of space, though we can quite well think it as empty of objects”.[6] We can imagine the absence of all objects in space but we cannot imagine the absence of space itself. The first argument presents the negative position that space is not empirical, the second argument says positively that it is a priori.

Third argument: “Space is not a discursive or, as we say, general concept of relations of things in general, but a pure intuition”.[7] Kant declares that there is only one space. When we speak of many spaces, we mean parts of that one and the same space.

Fourth argument: “Space is represented as an infinite given magnitude”. [8]This argument is based on third argument, where, Kant argues that we can conceive of only one space and the different spatial representations are parts of that unique space. This argument says that the concept of one space contains within itself, “…an infinite number of representations within itself”.[9] Therefore, it follows that the concept of one space, which contains within itself number of representations, cannot be derived from sensible intuition, and must be regarded as a priori.

These arguments are put forward in favor of the metaphysical exposition of the concept of space. Kant also puts forwards five arguments in favor of the concept of time. They are-

First argument of the concept of time: “Time is not an empirical concept that has been derived from any experience.”[10] The concept of time is presupposed as the coexistence and the succession of an object. According to Kant, “only on the presupposition of time can we represent to ourselves a number of things as existing at one and the same time (simultaneously) or at different times (successively).”[11] Hence, time is regarded as an a priori concept, because it presupposes for the representation of coexistence and the succession of an object.

Second argument: “Time is a necessary representation that underlies all intuitions. We cannot, in respect of appearances in general, remove time itself, though we can quite well think time as void of appearances. Time is, therefore, given a priori”.[12] Kant only in relation to time though time can be conceived without any representation. Kant believes that appearances may disappear, but time (which is the universal condition of all appearances) cannot be removed. He writes, “Appearances may, one and all, vanish; but time (as the universal condition of their possibility) cannot itself be removed”.[13]

Third argument: Time has only one dimension….” That is one after another. Different temporal representations are conceived in the one dimension of time. Time is a priori and hence it possesses the elements of certainty and necessity. Kant argues, “These principles cannot be derived from experiences, for experience would give neither strict universality nor apodeictic certainty”.[14]

Fourth argument: “Time is not a discursive, or what is called a general concept, but a pure form of sensible intuition. Different times are but parts of one and the same time; and the representation which can be given only through a single object is intuition”.[15] Time like Space is one. Different times are parts of that one time. The concept of time is a pure form of sensible intuition and hence it is regarded as a priori.

Fifth argument: “The original representation, time, must therefore be given as unlimited”. [16] This argument is based on the previous argument where Kant remarks on the concept of one time and the different representations of the coexistence and the succession of objects are conceive as the parts of that one time. Kant regards the concept of time as unlimited, where infinite representations of coexistence and succession of objects take place. He believes that the concept of time as unlimited cannot be derived from sensible intuition and must be regarded as a priori.

In the metaphysical exposition of space and time, Kant tries to prove that space and time cannot be derived from sensible intuition and therefore they must be regarded as a priori. Space and time are the presuppositions of the representation of any object and they must be regarded as the condition for the possibility of any representation. According to Kant, we can conceive of any one space and time and different representation are only parts of the one space and time which are infinite and unlimited. After that, Kant discuss the transcendental exposition of space and time and tries to show that every manifold of sensible intuition has to be received in the form of space and time so that, “…a priori synthetic knowledge can be understood.”[17]

By giving an example from geometry, Kant tries to prove the concept of space as synthetic a priori, and by giving an example from physics he tries to prove the concept of time as synthetic a priori. These two different examples make space and time as synthetic a priori in two different ways.

According to Kant, “Geometry is a science which determines the properties of space synthetically and yet a priori”.[18] Kant says that the proposition, “The sum of the three angles of a triangle is equal to two right angles”, is a synthetic proposition because in order to find a triangle and to find out the sum of its three angles as equal to two right angles, we have to take the aid of the sensible intuition. Therefore, Kant regards the proposition as synthetic. Again, this proposition expresses necessity and universality which can never be derived from sensible intuition. Therefore, the proposition can also be regarded as a priori.

In the transcendental exposition of the concept of time Kant argues that the third arguments puts forward in favor of the metaphysical exposition of the concept of time is properly belongs to the transcendental exposition. Kant says, “I may here refer to no.3, where, for sake of brevity, I have placed under the title of metaphysical exposition what is properly transcendental”.[19] Kant argues that the concept of time has only one dimension, i.e., one after the other. Kant holds that the concept of time possesses the elements of certainty and necessity and hence, it is regarded as a priori. At the same time, Kant argues that the concept of alteration and with it the concept of motion is possible only through the representation of time. Kant states, “Here I may add that the concept of alteration and with it the concept of motion, as alteration of place, is possible only through and in the representation of time.”[20] But every alteration is possible only in the concept of time which itself does not move: “Time itself does not after, but only something which is in time.”[21] Therefore, the concept of time explains the possibility of “a priori synthetic knowledge which is exhibited in the general doctrine of motion.”[22] Kant, in this way, tries to prove that our knowledge in physics or geometry is possible as synthetic a priori only by regarding the concept of space and time as synthetic a priori. Kant holds that the metaphysical exposition proves the concepts of space and time as a priori and transcendental exposition proves them as synthetic. And both the argument together proves the concept of space and time as a priori synthetic.

Kant holds that space and time are the two forms of human sensibility, through which we can obtain a priori synthetic knowledge. Pure mathematics is an example of this a priori synthetic knowledge. According to him, “Time and space are, therefore, two sources of knowledge, from which bodies of a priori synthetic knowledge can be derived. (Pure mathematics is a brilliant example of such knowledge, especially as regards space and its relations.) Time and space, taken together, are the pure forms of all sensible intuition, and so are what makes a priori synthetic propositions possible.”[23]

Kant distinguishes space and time from sensation. Space and time the pure forms of intuition and sensation is the matter of empirical intuition. Kant argues, “The former alone can we know a priori, that is, prior to actual perception; and such knowledge is therefore called pure intuition. The latter is that in our knowledge which leads to its being, called a posteriori knowledge, that is, empirical.”[24]

According to Kant, every object, in so far as it can be given in the manifold of sensible intuition, is subject to space and time. He therefore, regards space and time as empirically real. Kant regards the empirical reality of the concept of space as, “…all things, as outer experiences, are side by side in space, the rule is valid universally and without limitation…We assert, then, the empirical reality of space, as regards all possible outer experience….”[25]  At the same time, he states that space and time are transcendentally ideal, because they do not exist independent of the human mind. But the concept of space and time cannot be regarded as absolute realities and can never be applied to the things-in-themselves. Kant says, “…We can indeed say that space comprehends all things that appear to us as external, but not all things in themselves by whatever subject they are intuited…”[26] Similarly about the concept of time, Kant says, “…we deny to time all claims of absolute reality; that is to say, we deny that it belongs to things absolutely, as their condition or property, independent of any reference to the form of our sensible intuition; properties that belong to things in themselves can never be given to us through the sense.” [27] 

According to Kant things-in-themselves are the ground and cause of appearances, but space and time can never be applied to thing-in-themselves. Space and time can be applied to things only in so far as they can be given in sensible intuitions.  

But space and time as pure form of intuition is meaningless without the categories of understanding. According to Kant, there are two source of knowledge. They are intuition and the concepts. Through intuition an object is given to us and through concepts the object is thought in relation to representation. Neither concept without an intuition, nor intuition without concept, can yield knowledge.

Kant says that receptive capacity of the mind, its power of receiving the representations in which it is affected by the object is known as sensibility, and the capacity of the mind to produce these representations are known as the understanding.

Sensibility is the faculty of intuition and understanding is the faculty of concept. Sensibility and understanding are necessary for the knowledge of object. Through sensibility we apprehend the manifold of intuition and through the categories the manifolds are synthesized in the idea of object. Thus without concepts the intuition is blind and without intuition, the concept is empty. Knowledge is the joint product of both sensibility and understanding. He writes, “Without sensibility no object would be given to us, without understanding no object would be thought. Thoughts without content are empty, intuitions without concepts are blind.”[28]

The term category is borrowed from Aristotle who has made the first attempt to find out these fundamental concepts. There is a difference between Aristotle and Kant on the concept of category. Aristotle talks about ten categories while Kant talks about twelve categories.

Aristotle maintains that categories are the fundamental concepts of thought and at the same time they are the basic features of objective reality. He enumerates ten categories which are as follows: substance, quality, quantity, relation, place, time, position, state, activity and passivity.

But Kant is opposed to Aristotle’s views on categories. Criticizing Aristotelian categories, he says, “He merely picked them up as they came in his way”[29]. The differences between them regarding the categories arise out of their fundamental philosophical positions. Whereas for Aristotle, an object is the amalgamation of form and content, and is independent of the human mind; for Kant, an object is synthetic a priori aspects; i.e. the forms cannot exist independent of the human mind but they can exist independent of the synthetic aspects which constitute the content. Kant differs regarding the origin of the categories, because there “are to be found in it some modes of pure sensibility, and an empirical concept, none of which has any place in a table of concept that trace their origin to the understanding”[30].

Kant also agrees with Aristotle that the knowledge of an object is possible only through the categories. He also retains some of the categories already enumerated by Aristotle such as substance, quality, quantity, relation, position and state. According to Aristotle, categories provide both the form and content whereas in Kant they can provide only the form, and the content is given by the sensible-intuitions. For him, “thought without concepts are empty, and intuition without concepts are blind.”[31] 

The blindness of sensible-intuitions means their meaninglessness. In order to give them meaning, they have to be determined by the categories. Thus “our knowledge springs from two fundamental source of mind; the first is the capacity of receiving the representations, the second is the power of knowing an object through these representations.”[32]

According to Kant, a representation is that through which an object is given to us and it is possible when the thing-in-itself on our sense and thus produces the sensible intuitions. And the power of the mind of knowing the representations is for him the categories. In his analysis, categories and sensible intuitions, which together constituent the knowledge of an object, cannot interchange their functions. “The understanding can intuit nothing, the sense can think nothing.”[33]

Kant says that the rules for determining the sensibility, which provide the object of knowledge, are different from the rules of the understanding in general that is logic.

Kant regards logic in a twofold manner. They are logic of the general and the logic of the special employment of the understanding. Logic of the general, according to Kant, contains,”….the absolutely necessary rules of thought without which there can be no employment whatsoever of the understanding. It therefore treats of understanding without any regard to difference in the objects to which the understanding may be directed.”[34]

At the same time, the logic of the special employment of the understanding is regarded as particular logic differs from the general logic in the sense that the former is valid to the extent of a particular class of object while the letter is valid universality.[35]

According to Kant, general logic may be pure or applied. General logic is pure, when we abstract it from all the empirical conditions under which our understanding is exercised. Kant gives certain instances like- the influence of the senses, the play of imagination, the laws of memory, the force of habit, inclination, etc., where understanding exercises under certain circumstances, and to become acquainted with these circumstances experience is required. He says, “pure general logic has to do, therefore, only with principles a priori, and is a canon of understanding and of reason…”[36]

Kant regards understanding as a “faculty of judgment.”[37] Judgment is the function of understanding. But according to him, function means, “….the unity of the act of bringing various representations under one common representation.”[38] Every judgment consist of concepts and “the only use which understanding can make of these concepts is to judge by means of them.”[39] Consequently, “The knowledge yielded by understanding, must therefore by means of concepts…”[40] The concepts, which are used in a judgment, can be used in various other representations. Kant says. “In every judgment there is a concept which holds of many representations, and among them of a given representation that is immediately related to an object.”[41] He expounds twelve kinds of judgments and relates them with the corresponding concepts.

Kant divides all kinds of judgments into four main heads- quantity, quality, relation and modality, but deals with them separately and does not show any interrelation. Each head contains three subdivisions which are interrelated.

Under quantity, the judgment is universal, particular or singular. “All men are mortal” is a universal judgment, because the concept of the subject is universally applicable to the concept of the predicate. In every universal judgment a concept of unity is involved. He deduces the concept of unity from the proposition “All S are P”.

Under quality, the judgment is either affirmative, negative or infinite. “All men are mortal” is an affirmative judgment because the concept of subject has a positive predicate. In an affirmative judgment a concept of reality is involved. Kant deduces the concept of reality from the judgment in which the concept has a positive predicate.

Under relation, judgments are categorical, hypothetical and disjunctive. Kant says that in a categorical judgment, two concepts are involved, in a hypothetical judgment, two judgments are involved, and in a disjunctive judgment, several judgments are involved. Categorical judgment like all men are mortal, two concepts are involved the class of men and the class of mortal beings. Hypothetical judgment, such as, ‘if there is s perfect justice, the obstinately wicked are punished’. This judgment contains the relation of two propositions, namely, ‘there is a perfect justice, and the ‘obstinately wicked are punished’. Disjunctive judgment contains the relation of two or more propositions. In a disjunctive proposition, one proposition may exclude the other proposition, but jointly they give the complete knowledge of the world. Kant gives an example of the disjunctive judgment like, ‘the world exists either through blind chance, or through inner necessity, or through an external cause’. Each of these propositions gives us a part of the knowledge of the existence of the world. But together they can provide us the complete knowledge. Kant says in a disjunctive judgment the concept of community is involved. He says, “…in a disjunctive judgment a certain community of the known constitutes, such that they mutually exclude each other, and yet there by determine in their totality the true knowledge.”[42]

Under modality, judgments are problematic, assertoric and apodeictic. Kant argues that in a problematic judgment, affirmation or negation is merely possible. For example, ‘earth exist through an external cause’ is a problematic judgment because it either can possibly affirm or denied. In an assertoric judgment, affirmation or negation is viewed as real. ‘There exists a perfect justice’ is an assertoric judgment, because the existence of perfect justice is merely an assertion. In an apodeictic judgment, affirmation or negations are viewed as necessary ‘Socrates must be mortal’ is an apodeictic judgment, because it expresses necessity and excludes contingency’.  

 According to Kant, the categories are “Original pure concepts of synthesis that the understanding contains within itself a priori.”[43] On this basis, he considers Aristotle’s position on categories as defective because the latter “merely picked them up as they came in his way.” [44]Kant states that Aristotle derives categories from sensibility while it has no place in the categories “that trace their origin to the understanding.”[45] He regards categories as a priori. But categories are empty if they are not applied to the sensible intuitions which are the objects of knowledge. Therefore, categories and sensible intuitions must come together in order to give knowledge of something.

Kant discuss categories of understanding in two heads-one is transcendental deduction of categories and other is metaphysical deduction. He makes a distinction between these two, in the transcendental deduction of categories, the concept do not contain anything empirical, yet serve as that a priori condition of all empirical objects. On the other hand, Kant argues that, in the metaphysical deduction of categories the concepts are derived from the experience and reflection upon experiences.

Kant only insists upon the transcendental deduction of the categories and not of the empirical deduction. In the transcendental deduction Kant explain three subjective sources of knowledge- sense, imagination, and apperception. These three subjective sources viewed as empirical, in its application to give appearances. All of them are a priori elements, which makes empirical employment itself possible.

Kant says that knowledge arises only when sensible intuitions are brought under the categories of understanding. The pure concept of understanding must be applicable to the sensible intuitions. The representation of an object must be homogeneous with the concept. Kant says that, “In all subsumptions of an object under a concept the representation of the object must be homogeneous with the concept; in other words, the concept must be contain something which is represented in the object that is to be subsumed under it.” It means that an object is contained under a concept. For example, the empirical concept of a plate is homogeneous with the pure geometrical concept of a circle. The roundness which is thought in the latter can be intuited in the former.

Sensible intuition and categories of understanding are heterogeneous. The sensible intuitions have an empirical content, but the categories of understanding devoid of any empirical content. Now a question arise, if the categories of understanding devoid of any empirical content, then how the application of a category to appearances possible? In fact this is the problem of transcendental deduction. Kant argues that through transcendental schema, forms of sensibility are brought to the categories of understanding.

In Kantian philosophy a transcendental schema is process by which a category or pure, non-empirical concept is associated with a sense impression. Kant says that, pure concept of understanding being quite heterogeneous from empirical intuitions, and indeed from all sensible intuitions and never met with in any intuition. Here Kant imagines a third thing which is homogeneous with category on the one hand and on the other hand with the appearance, and which thus makes the application of the category with appearance possible. The schema is nothing but a transcendental determination of time. Kant says that, “Obviously there must be some third thing, which is homogeneous on the one hand with the category, and on the other hand with the appearance, and which thus makes the application of the former to the latter possible. This mediating representation must be pure, that is, void of all empirical content, and yet at the same time, while it must in one respect be intellectual, it must in another be sensible. Such a representation is the transcendental schema.”[46] Transcendental schema serves to link the categories with objects and thereby supplies a reference, a meaning to the former.

Kant makes a distinction between an image and a schema because both are the product of imagination. Schema must not be confused with a picture or image. A schema enables us to form an image of the concept, but in itself, it is not an image. On the other hand, we think of number in general, by which we can form an image of any number, we have a schema, and not an image.

Kant says that all knowledge to its object carries with it an element of necessity. The object is viewed as that which prevents the modes of knowledge to become arbitrary and determines this knowledge as a priori. There is a unity between knowledge and the concept of the object. He says that, “For in so far as they are to relate to an object, they must necessarily agree with one another, that is, must possess that unity which constitutes the concept of an object”[47]. He argues that the unity, which the object makes, is the formal unity of consciousness in the synthesis of the manifold of representations. It is only when we produce the synthesis unity in the manifold of intuition, Kant says that we are in a position to say that we know the object. He says, “This unity of rule determines all the manifold, and limits it is conditions which make unity of apperception possible.”[48]

According to Immanuel Kant, the highest unity of self-consciousness which under lies all synthesis. The unity of self-consciousness is the supreme principle under which all the thinkable must be brought and which makes itself possible.

According to Kant self-consciousness is neither a substance with an attribute of consciousness, nor self is a series of perception held together in the form of a bundle. Kant states that, all our knowledge of objects pre-suppose a unity of self-consciousness. Kant’s main argument against the bundle theory of self can be brought home with the help of an analogy. Take a sentence which consists of seven letters. If we give these seven letters to seven person distributing one each, will they ever be able to know the meaning of the sentence? A sentence is meaningful only if all the seven letters are presented to a single person. Similarly, each distinct percept can become meaningful only if they are subjected to a unity. This is known as unity of self-consciousness. Kant says this unity of self-consciousness is a formal unity not a substantial unity. In the absence of a unitary self-consciousness it is not possible to relate the given sense data to an object of knowledge. An object is an object for us only if the relevant sense-manifolds are systematically interrelated and it is this process of interrelating synthesis which pre-supposes a self.

Now, it is beyond doubt that self as a collection of momentary selves doesn’t at all exist. There is a unitary self which is conscious of its own activity. Kant calls it ‘Transcendental unity of Apperception.’ This can be interpretive in two ways. It can be either as power or as an act. As an act, it is identical with self consciousness or ‘I think’. The idea of ‘I think’ is a formal unity. It has no content of its own. Therefore, in order to be aware of this unity, I must be aware of some objects in space and time. Self consciousness presupposes the consciousness of object. In order to be self-conscious there must be some object upon and through which it becomes conscious of itself.

Kant believes that this transcendental unity of apperception is formed out of all possible appearances, according to laws. This is not possible if the mind is not conscious of the identity of function that synthetically combines all appearances in one knowledge. The original and necessary consciousness of the identity of self is also the consciousness of the synthesis of all appearances. Kant says that we do not find the order and regularity in the appearances, rather we introduce them. Kant remarks, “Thus the order and regularity in the appearances, which we entitle nature, we ourselves introduce. We could never find them in appearances, had not we ourselves, or the nature of our mind, originally set them there. For this unity of nature has to be a necessary one, that is, has to be an a priori certain unity of the connection of appearances; and such synthetic unity could not be established a priori if there were not subjective grounds of such unity contained a priori in the original cognitive powers of our mind, and if these subjective conditions, in as much as they are the grounds of the possibility of knowing any objects what so ever in experience, were not at the same time objectively valid.”[49] The unity of apperception, therefore, Kant says, is the transcendental ground of all appearances in one experience.

In the above the author have discussed about Kant’s epistemological position. He makes a distinction between epistemology and ontology. According to him, our knowledge is limited to the world of phenomenon and the knowledge of noumenon is something unknown and unknowable.


  • I. Kant (1973). Critique of Pure Reason, translated by N. K. Smith, p. 68.
  • R.P. singh, R.P (1987). A Critical Examination of Immanuel Kant’s Philosophy, p. 48

About the author: The author, Srirupa Datta Choudhury completed her H.S. in 2007 from Dharmanagar Govt Girls H. S. (+2) stage school. Then She completed  B. A. in 2010 from Dharmanagar Government Degree collage. After that she completed PGRD in 2011 from IGNOU, and then completed M. A. in 2013 from Assam University, then she Joined in Tripura University, Department of Philosophy as a research Scholar in 2013.

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