Immanuel Kant


“Two things fill my mind with ever-increasing wonder and awe, the more often and the more intensely the reflection dwells on them: the starry heavens above me and the moral law within me,” is the statement carved on the gravestone of Kant in Königsberg. Immanuel Kant was a German philosopher and is one of the most important and influential figures in Western philosophy. His system presents a landmark in the history of philosophical thought. Kant’s most important books are his three Critiques, Critique of Pure Reason, Critique of Practical Reason and Critique of Judgment. Kant compared himself to Copernicus and claimed his work to have brought about a Copernican revolution in Philosophy. It might be considered an exaggeration, but there is no doubt about the significant influence of Kant on subsequent philosophers. He attempted to reconcile the two opposing philosophies of rationalism and empiricism. Rationalism, by its stress on reason, had guaranteed certainty of knowledge but raised doubts about its practical contents. Empiricism, by making experience the source of knowledge, had secured the practical contents, but at the sacrifice of certainty.

Kant was a university professor, and in his early period had studied the philosophy of Leibniz. Then he read Hume’s Inquiry into Human Understanding and his skepticism greatly troubled him. Encounter with Hume’s philosophy, as Kant describes himself, awakened him from his “dogmatic slumbers”[1]. But Hume was, for Kant, a rival philosopher to be refuted. Rousseau had a more deep and positive influence, whose insistence that religion does not need reason as its foundation had a profound effect on Kant’s moral philosophy. The questions with which Kant’s philosophy are related are best summarized by Kant himself, “All the interests of my reason, speculative as well as practical, combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?”[2]

Kant believes knowledge to be indisputable. It would be self-contradictory to deny knowledge, because the denial is itself based on knowledge and is knowledge itself. So, Kant does not accept the position that no knowledge is possible. We do possess judgments, this is unquestionable. So, we must begin with the analysis of these judgments.

Judgments can be classified in various ways. One distinction is between a priori and a posteriori propositions, according to their origins. An a priori proposition is known independently of experience, in fact, even before any experience. An a posteriori proposition (or an ‘empirical’ proposition) is derived from our experience and sense perception. For example:
‘2 + 2 = 4’ is an a priori proposition; ‘America was discovered by Columbus’ is an a posteriori proposition and can only be known through experience.

Kant made another distinction, which was undistinguished in Leibniz’s philosophy. There are ‘analytic’ and ‘synthetic’ propositions. An analytic proposition is one in which the predicate is part of the subject. For example, ‘All old men are men’. All analytic propositions are true because it would be self-contradictory to deny them [‘All old men are not men’]. A synthetic proposition is one, which is not analytic i.e. the concepts of its subject and predicate are independent. For example, ‘All old men love to play with their children’ is a synthetic proposition.

[This distinction is generally held to be the same as between ‘necessary’ and ‘contingent’ truths. A necessary truth is a proposition which it would be self-contradictory to deny, and hence is always true. A contingent proposition may or may not be true. For example:
‘A hexagon has six sides’ is necessary because it would self-contradictory to say ‘A hexagon does not have six sides.’ ‘Pan cakes are round’ is a contingent statement because it may or may not be true.]

Earlier philosophers had held the a priori / a posteriori distinction to be synonymous with analytic/synthetic distinction, but Kant did not agree with it. He maintained that the two distinctions were not completely coincident and one could consider four possible logical combinations.

1) Analytic a posteriori judgements do not arise because we don’t need to learn from experience what is necessarily true.
2) Synthetic a posteriori judgements we derive from our experience.
3) Analytic a priori judgments are necessarily true and include logical truths.
4) Synthetic a priori judgments are the judgements which cannot be shown to be true by mere analysis of their subject-predicate relationship and use of contradiction, but are nevertheless true and independent of experience.

Previous philosophers, Kant maintained, had been led into trouble because they had not considered synthetic a priori judgements. Hume had believed mathematics to be analytic a priori and hence had considered them safe from his skepticism, but Kant states that mathematical truths are synthetic a priori. Hume had shown that the law of causality is not analytic, and therefore, we could not be certain of its truth. Kant replied that although it is not analytic but it is still a priori. So, now Kant is faced with his central issue:

How are synthetic a priori judgements possible? The Critique of Pure Reason is an answer to this question.

Before Kant, philosophers had concerned themselves with the nature of the object from which we receive different sensations, but Kant sought to study ‘knowing’ instead of ‘being’, i.e. how do we know? He believes that synthetic a priori judgements have a basis in the inherent structure of our mind, the natural manner in which our thinking operates. Kant calls this philosophy transcendental because it transcends the sense-experience. Transcendental philosophy, as Kant defines it, is a systematic exposition of all that is a priori in human knowledge, or ‘the principles of pure reason’. There are two stages in which the raw sensations are converted into finished product of thought. The first stage is the coordination of sensations by the application of forms of perception—space and time. The second stage is the coordination of perceptions into conceptions. Kant calls the study of first as Transcendental Aesthetic and the second as Transcendental Logic.

Empiricists had regarded mind as a tabula rasa, as a passive wax, which was blown into shape by the application of sensations. They failed to realize that the mind is not just a passive organ, merely receiving sensations, but it is an active selective, coordinative and directive organ, which transforms sensations into ideas. They failed to see that the mind receives sensations but perceives objects.

Sensation is an awareness of a stimulus, and each sense independently receives a different sensation. Tastes on the tongue, noise in the ear, and flash of light in the eyes are all sensations. These are not yet knowledge. The mind actively groups these sensations about a ‘thing’ in space and time, and then we are aware of an ‘object’—this is Perception. It is the coordination of sensations into knowledge.

Space and time are present inside in our mind, and have no existence outside it. In perception, the part, which is caused by the object, is sensation, but the part due to our subjective apparatus is called forms of perception. Since it is not a part of the sensation, it is not a part of the objective world. Space and time are essential a priori ideas and are necessary condition of all perceptions. They are “pure forms of sensible intuition” under which we perceive everything as being located in space and time. If a person wears red glasses, he will perceive everything as coloured red. Similarly, we can say that our mind wears the spatio-temporal glasses, and everything we perceive must be in space and time.

Leibniz had maintained that space is produced by our minds; Newton held that space was absolute. Kant said that space is objective when applied to objects, as they appear to us, but it is subjective when the objects are considered as things-in-themselves, independent of our perceptions.

Space and time are a priori as all perception involves and pre-supposes them. We can’t think of something which is neither in space, nor in time, because we can’t take off the ‘glasses of space and time’ from our perceptions. Thus laws of mathematics are also a priori because they are the laws of space and time.

Kant believes in things-in-themselves to be the cause of sensations but maintains that they are unknowable; they are are not in space and time, because space and time are our forms of perception. This means that mathematics can be applied to everything we perceive but can’t be applied to the external world, when considered independently of our perception.

The next step is the Transcendental Logic, the transformation of perceptions into conceptions, of experience into science. By Transcendental Aesthetic, an object is received by us; by Transcendental Logic, it is thought of in the mind. The former uses intuition, the latter uses concepts. Transcendental Logic is the science of rules of understanding.

The a priori concepts used in the understanding are classified by Kant into twelve ‘categories’:

1) Of Quantity: Unity, Plurality, Totality
2) Of Quality: Reality, Limitation, Negation
3) Of Relation: Substance and Accident, Cause and Effect, Action and Reaction
4) Of Modality: Possibility, Existence, Necessity

These are also subjective like space and time, and are applicable to the phenomenon we observe. These categories form the essence and character of mind. Note that Cause-and-Effect is one of these categories, and hence, Kant claims that the idea of causality is a priori as well as being synthetic. Hence, it is a part of our inherent understanding to think of phenomenon in terms of cause and effect, and the concept of cause is present prior to all experience, but it is applicable only to our thinking, and not to the thing-in-itself.

Kant makes a strict distinction between Phenomena and Noumena. The object as it appears to us is the phenomena. The original objects, which constitute the reality, the thing-in-itself (Ding an sich), are the noumena. Kant maintains that the noumena are unknowable, and we can never know their reality; we remain utterly ignorant of it. All our synthetic a priori judgments can apply only to the realm of phenomena. We can know nothing certain about the thing-in-itself, apart from its existence.

A large number of false metaphysical beliefs arise from the applications of intuitions and concepts to the thing-in-itself. When science tries to explain the thing-in-itself, it finds itself confronting ‘antinomies’ and when theology attempts to do so, it is lost in ‘paralogisms’. Kant mentions four such antinomies in his Critique, which are insoluble problems. For example, consider the idea that the world had a beginning in time, but what was there before time? We can’t imagine the condition of no time. Now, consider the opposite idea that the world had existed since eternity. We can’t think of eternity as well. Similar is the question whether space is limited or infinite. If space is limited, then what is present beyond space? And the idea of infinite space is equally unsatisfying. We can’t answer these questions because we are trying to apply our reason to things, to which it can’t be applied. Space and time are modes of perception and do not belong to the external reality.

Now, Kant proceeds to refute all the ‘rational’ proofs of the existence of God in an attempt to show that reason cannot be used to prove God’s existence. We have seen the Ontological Argument and the Cosmological Argument before. Another argument is the Physico-theological proof. It is the popular argument from design, stating that the nature reveals a harmony and order that can only be explained by the existence of divine designer. Kant treats this argument with respect but maintains that at its best it only proves an architect and not a creator. This argument also does not prove the attributes which are associated with the concept of God and which the other logical arguments claimed to prove as well. For example, it doesn’t prove the unity of God; it doesn’t prove that the attributes of God are of infinite magnitude; it doesn’t prove that God is benevolent, or that God is omnipotent or omniscient, etc and can’t be used as an adequate conception of God[3]. Hence, Kant showed that religion couldn’t be proved by pure reason.

Let us now turn to Kant’s ethical theory, which has been developed in The Critique of Practical Reason and Metaphysics of Morals. Kant maintains that a ‘good will’ is something that is intrinsically good. It can be thought of being good without any qualifications—all persons know what a good will is. It is also independent of the consequences of the action, which is being intended. Kant’s ethical theory is therefore deontological i.e. actions are morally right because of the intentions, which must be derived from a sense of duty. Moral worth exists only when an action is done from a sense of duty, and not out of inclination or any other reason. According to this theory, a shopkeeper who is honest because of the fear of police is not virtuous, but a shopkeeper who is honest because he feels it his duty, is. Kant believes that morality must be based on a moral law, which is universal and is capable of being applied to any person at any place.

Kant brings out his idea of law. All things in nature act according to law, but man has the freedom to obey the moral law. Apart from being aware of the moral law, he also has some personal desires and self interests, and the interaction of the two results in the feeling of obligation, or an imperative, a command to act in a particular way.

There are two types of imperative. A hypothetical imperative states, ‘You must do A if you wish to achieve B’ i.e. it commands an action due to an end in purpose. The categorical imperative simply states ‘You must do A’ regardless of its consequences. Kant believes in the categorical imperative and maintains that it is a priori as well as being synthetic.

Using the idea that the moral law should be universal, Kant states the categorical imperative as: “Act only according to that maxim whereby you can at the same time will that it should become a universal law” i.e. you should act in such a way that you can wish that all the other people in the world also do the same. For example, you can lie to achieve some benefit, but you can’t wish that everyone in the world should lie, because then there would be no promises at all. A thief may steal but he can’t wish that everyone in the world should start stealing. An action is wrong when you do it yourself but wish that it should not be done to you; the thief would not wish his possessions to be stolen.

Kant also expressed a different version of the moral law to treat men as end: “Act in such a way that you treat humanity, whether in your own person or in the person of another, always at the same time as an end and never simply as a means.” This leads to the same actions as prescribed by the categorical imperative. For example, when a thief robs a person, he is treating him as a means to get money, and not as an end-in-itself.

Kant maintains that since humans can feel these moral obligations, it means that we are free. How could we ever conceive of the idea of duty if we did not feel ourselves to be free? Hence, the freedom, which could not be proved by theoretical reason, can be proved by the moral sense.

But although we feel a moral obligation to act, the act is not always awarded in this world. Often, those using immoral means achieve greater benefits than a virtuous man. And yet, knowing that we may not be justly rewarded in this world, we still feel that command to do the right thing. This could be possible only if at the bottom of hearts we knew that this life is not the end, and that there is a life to come after it in which we shall be justly rewarded. So, Kant claims that our moral sense proves the existence of a world hereafter.

Finally, Kant maintains, that the presence of the innate moral sense requires us to believe in a lawgiver i.e. in the existence of God. Our moral sense commands us to believe in such a being. Hence, all the religious elements that Kant had demolished by pure reason were restored by the application of practical reason.

Kant’s philosophy is far from being safe from criticism, and has been severely criticized by a number of subsequent philosophers. His arguments for the subjectivity of space and time have been shown to be flawed. For example, Kant maintained that space is an intuition because geometry is known a priori and is synthetic, and geometry utilizes the idea of space. And, similarly, arithmetic utilizes time and arithmetic is synthetic a priori. But the fact is that geometry is a term covering two different studies: Euclidean geometry, which is pure geometry and the Non-Euclidean geometry used in certain branches of physics such as theory of general relativity. The former is a priori but not synthetic, while the latter is synthetic but not a priori[4]. Mathematicians have also proved that arithmetic is not synthetic, as Kant had thought. If we adopt the point of view used in Physics, qualities in percepts are different from their unperceived causes but there is a certain correlation between the two. For example, there is a correlation between the colors and the wavelengths. On similar basis, we can say that there are two spaces. One subjective and one objective, and there is a similar correlation between the two as between colors and wavelengths. But the case with time must be different; the subjective time must be equal to objective time. Supposes that you are speaking to A, you hear him, you give a reply, and he hears you and replies back. For you, A’s speaking and his hearing of your reply is in the unperceived world. If the conversation is to be successful, the temporal order of events must be the same in both subjective and objective sense.

Then there is the Kantian view of thing-in-itself, which Kant supposed to be the cause of our sensations. But as Kant himself maintains, the idea of cause-and-effect is one of the categories of concepts and is a part of our subjective apparatus. Hence, there was no valid reason for Kant to assume that our sensations had a cause. The idea of thing-in-itself was abandoned by his immediate successors—Fichte, Schelling and Hegel—who developed an idealist philosophy out of Kant. It should also be noted that Kant set out to combat the skepticism of Hume, but his own philosophy represents an extreme skeptical position: we can know nothing, nothing at all, about the thing-in-itself. We can never know that the truth about reality. What more skepticism can there be! It is not surprising that Kant’s philosophy, when extended by the idealists, resulted in something not very different from Solipsism, the belief that the self is the only thing that exists, or that can be known and verified.

Kant’s moral philosophy is also a weak point, in which Kant had attempted to reconstruct what he had demolished of religion. The second Critique is also sometimes sarcastically called ‘Transcendental Anesthetic’! Kant’s belief in an innate, a priori moral sense created by God in us was shown wrong in the light of theory of evolution. The moral sense is not God-gifted but a product of evolution of man. It is the mode of conduct developed by attempts at group survival in the continual strife of life. Also, Kantian ethics gives no credit to a benevolent impulse. A person who is kind to his brother because he loves him is not virtuous according to Kant because he is not acting out of a sense of duty. This principle is also limited because it makes no account of the consequence of an action.


[1] Russell, however, adds that he soon invented a soporific and went to sleep again!
[2] Kant, Critique of Pure Reason
[3] The argument from design has been severely weakened by the theory of evolution by means of natural selection by Charles Darwin. Natural Selection provides a scientific mechanism by which organisms evolve with increasing complexity as if they have been ‘designed’ by some supernatural force. It is not the purpose of this book to discuss the arguments for God’s existence in detail. For those interested, I’ll strongly recommend Philosophy of Religion by John Hick.
[4] See Bertrand Russell, History of Western Philosophy, Routledge, London, page 688