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Immanuel Kant

Immanuel Kant was a German philosopher during the Enlightenment era of the late 18th century. His best-known work is the 'Critique of Pure Reason.'

(1724-1804)

Who Was Immanuel Kant?

While tutoring, Immanuel Kant published science papers, including "General Natural History and Theory of the Heavens" in 1755. He spent the next 15 years as a metaphysics lecturer. In 1781, he published the first part of Critique of Pure Reason . He published more critiques in the years preceding his death on February 12, 1804, in the city of his birth.

Kant was the fourth of nine children born to Johann Georg Cant, a harness maker, and Anna Regina Cant. Later in his life, Immanuel changed the spelling of his name to Kant to to adhere to German spelling practices. Both parents were devout followers of Pietism, an 18th-century branch of the Lutheran Church. Seeing the potential in the young man, a local pastor arranged for the young Kant's education. While at school, Kant gained a deep appreciation for the Latin classics.

In 1740, Kant enrolled at the University of Konigsberg as a theology student, but was soon attracted to mathematics and physics. In 1746, his father died and he was forced to leave the university to help his family. For a decade, he worked as a private tutor for the wealthy. During this time he published several papers dealing with scientific questions exploring the middle ground between rationalism and empiricism.

Full-Fledged Scholar and Philosopher

In 1755, Immanuel Kant returned to the University of Konigsberg to continue his education. That same year he received his doctorate of philosophy. For the next 15 years, he worked as a lecturer and tutor and wrote major works on philosophy. In 1770, he became a full professor at the University of Konigsberg, teaching metaphysics and logic.

In 1781, Immanuel Kant published the Critique of Pure Reason , an enormous work and one of the most important on Western thought. He attempted to explain how reason and experiences interact with thought and understanding. This revolutionary proposal explained how an individual’s mind organizes experiences into understanding the way the world works.

Kant focused on ethics, the philosophical study of moral actions. He proposed a moral law called the “categorical imperative,” stating that morality is derived from rationality and all moral judgments are rationally supported. What is right is right and what is wrong is wrong; there is no grey area. Human beings are obligated to follow this imperative unconditionally if they are to claim to be moral.

Later Years and Death

Though the Critique of Pure Reason received little attention at the time, Kant continued to refine his theories in a series of essays that comprised the Critique of Practical Reason and Critique of Judgement. Kant continued to write on philosophy until shortly before his death. In his last years, he became embittered due to his loss of memory. He died in 1804 at age 80.

QUICK FACTS

• Name: Immanuel Kant
• Birth Year: 1724
• Birth date: April 22, 1724
• Birth City: Konigsburg (now Kaliningrad)
• Birth Country: Prussia (now Russia)
• Gender: Male
• Best Known For: Immanuel Kant was a German philosopher during the Enlightenment era of the late 18th century. His best-known work is the 'Critique of Pure Reason.'
• Education and Academia
• Astrological Sign: Taurus
• Nationalities
• Death Year: 1804
• Death date: February 12, 1804
• Death City: Konigsburg (now Kaliningrad)
• Death Country: Prussia (now Russia)

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Immanuel Kant: Life, Philosophy and Legacy

Biography | Influences | Core Philosophy | Essential Works | Reception | Criticisms | Legacy

Immanuel Kant (1724-1804) was a German philosopher who is widely regarded as one of the most important thinkers of the Enlightenment era and a key figure in Western philosophy, renowned for his work in epistemology, metaphysics and ethical philosophy.

Kant’s philosophical framework is best known for the concept of Transcendental Idealism, which sought to bridge the gap between rationalism and empiricism , while addressing the skepticism raised by David Hume . In his magnum opus, The Critique of Pure Reason , he argued that our knowledge is not solely derived from sensory experience (empiricism) or innate ideas (rationalism), but is shaped by the interaction between the mind and the external world.

Transcendental Idealism distinguishes between phenomena – things as they appear to us – and noumena – the things-in-themselves, which are beyond our sensory experience – and introduces the notion of the a priori synthetic judgments: fundamental truths are known independently of experience, yet contribute to our understanding of the world.

According to Kant, certain fundamental principles, such as those governing space, time and causality, are inherent in the structure of the human mind. These a priori synthetic judgments form the necessary conditions for human experience, representing the essential building blocks that allow us to comprehend and organize the sensory data we receive from the external world.

Kant’s transcendental idealism asserts that while we can never know the things-in-themselves, as they exist independently of our perception, we can have knowledge of the world as it appears to us; for knowledge is not a mere reflection of external reality but is actively shaped by the cognitive framework of the human mind.

This perspective transformed epistemology and laid the foundation for the development of German Idealism, influencing subsequent philosophical movements such as Phenomenology and Existentialism.

Kant’s moral philosophy, expounded in “Groundwork for the Metaphysics of Morals” and “Critique of Practical Reason”, presents the notion of the categorical imperative, declaring that one should act according to maxims that could be consistently willed to become universal laws. His moral philosophy, known as Kantian ethics, has been lauded for offering a rational perspective on morality.

Table of Contents

Immanuel Kant was born on 1724 Prussia (now Russia). Growing up in a pious Pietist family, he received a strict religious upbringing that instilled in him a sense of discipline and moral values, however, his curiosity extended beyond religious teachings, and he developed a keen interest in natural science and philosophy.

Kant attended the Collegium Fridericianum, a Pietist grammar school, where he excelled in Latin, classical literature and philosophy. In 1740, he enrolled at the University of Königsberg, studying theology, mathematics, physics and philosophy. It was during this time that he encountered the works of influential thinkers such as Isaac Newton, John Locke and Christian Wolff.

After completing his studies, he worked as a private tutor to support himself financially. In 1755, he earned his doctorate in philosophy and began lecturing at the University of Königsberg as a Privatdozent. His lectures covered a wide range of subjects, including logic, metaphysics, ethics and anthropology.

Kant’s academic career flourished, and in 1770, he was appointed as a full professor of logic and metaphysics at the University of Königsberg. He held this position for over 40 years until his retirement in 1796. Notably, his intellectual pursuits extended beyond philosophy, and he also made significant contributions to physics, astronomy and anthropology.

As a prolific writer, Kant published numerous works on philosophy, ethics and aesthetics, earning him recognition as one of the leading intellectuals of his time. His major works, including The Critique of Pure Reason , Groundwork for the Metaphysics of Morals and the Critique of Practical Reason solidified his reputation as an esteemed philosopher.

Intellectual Influences

Immanuel Kant lived in a period known as the Enlightenment era, a pivotal time in history marked by significant cultural, intellectual and philosophical developments.

The Enlightenment, which spanned the 17 th and 18 th centuries, affirmed reason to be the primary source of reliable knowledge and advocated for the application of scientific methods to various aspects of human life. This era saw a departure from the unquestioned reliance on authority and, with an increasing focus on individual autonomy and critical thinking. Enlightenment thinkers sought to challenge religious dogma and absolute monarchy, aiming to create a more rational and just society.

Two dominant and antagonistic philosophical positions of the time were rationalism and empiricism. Rationalists, such as René Descartes and Gottfried Wilhelm Leibniz , believed that knowledge could be attained through reason and that the mind possesses innate ideas that do not rely on sensory experience. On the other hand, empiricists, like John Locke and George Berkeley , asserted that all knowledge comes from sensory experiences and that the mind is initially a “blank slate”, or tabula rasa. Empiricism stressed the importance of observation and experimentation as the foundation of knowledge.

David Hume , a Scottish philosopher and one of Kant’s most significant influences, presented a radical form of skepticism that had a profound impact on Kant’s thinking. Hume’s philosophy challenged the traditional notions of causality and induction, raising doubts about the validity of cause-and-effect assertions.

Kant found Hume’s skepticism deeply troubling, as it seemed to undermine the grounds for scientific knowledge and the very possibility of certain knowledge. In response, Kant embarked on what he termed a “Copernican revolution” in philosophy. He sought to reconcile the seemingly conflicting views of rationalism and empiricism, by proposing a new approach to epistemology and metaphysics.

Kant’s critical philosophy aimed to investigate the conditions of human knowledge and the limitations of reason. He argued that while our knowledge begins with sensory experience, the mind actively shapes and structures this experience, giving rise to a priori synthetic knowledge.

Kant’s synthesis of rationalist and empiricist elements laid the groundwork for transcendental idealism, where he posited that knowledge is limited to phenomena (appearances), while the ultimate nature of reality, the noumena, remains beyond human grasp.

Kant’s response to Humean skepticism and his unique synthesis of philosophical positions became a turning point in Western philosophy. His critical philosophy not only addressed the philosophical challenges of his time but also set the stage for future philosophical debates and inquiries, shaping the trajectory of modern philosophy as we know it today.

Core Philosophical Framework

Immanuel Kant introduced two central ideas that profoundly influenced the course of Western philosophy: transcendental idealism and the categorical imperative.

Transcendental Idealism

Kant’s concept of transcendental idealism lies at the heart of his critical philosophy. He argued that our knowledge is not a direct reflection of an external reality, but rather a product of the interaction between the mind and the external world.

Kant made a clear distinction between two realms of existence: phenomena and noumena. Phenomena refer to the appearances of things as they appear to us, shaped and organized by the mind’s faculties. These appearances are the objects of our experience, and their properties are dependent on the ways our mind structures and perceives them. In other words, our knowledge is limited to the world of appearances, as we can only know objects as they appear to us. On the other hand, noumena represent the things-in-themselves, the underlying reality that exists independently of our perceptions. However, he argued that we can never directly know the noumenal realm and that our understanding is confined to the boundaries of human cognition, which constructs the phenomenal world.

While traditional philosophical thought categorized knowledge as either empirical (derived from experience) or a priori (known independently of experience), Kant proposed a new category: synthetic a priori knowledge . He contended that certain fundamental truths, such as mathematical and metaphysical principles, are not based on experience but are also not purely analytical. These truths are synthetic, meaning they involve the combination of ideas, and yet they are known a priori, that is, prior to experience.

Kantian Ethics

Kant’s moral philosophy, known as deontological ethics, focuses on the concept of moral duty and universal principles. At the core of his ethical theory lies the categorical imperative, a fundamental principle that guides moral decision-making. According to Kant, morality is not contingent on outcomes or consequences, but on the inherent nature of actions themselves.

The categorical imperative states that one should act in a way that the principles governing their actions could be applied universally, without contradiction. In other words, an action is morally right if it is based on a principle that could be universally adopted. Kant’s deontological ethics also stresses the importance of autonomy and rationality in moral decision-making. He believed that moral agents, as rational beings, possess the capacity to act according to universal principles and moral laws, irrespective of their desires or inclinations.

Through the categorical imperative, Kant sought to provide a universal moral framework that is independent of cultural or situational variations.

Immanuel Kant’s Essential Works

Immanuel Kant’s essential works – Prolegomena to any Future Metaphysics , Critique of Pure Reason and Groundwork of the Metaphysics of Morals – provide a thorough yet accessible overview of his philosophy, encompassing his epistemological inquiries, metaphysical insights and moral theories, from the exploration of human knowledge to the formulation of the categorical imperative.

Prolegomena to any Future Metaphysics

The “Prolegomena” is a work that serves as a preamble or introduction to Kant’s more extensive and complex Critique of Pure Reason , as he wrote this book in response to misunderstandings and criticisms of the “Critique”, seeking to provide a more accessible overview of his philosophy.

In the “Prolegomena”, Kant addresses the scope and limits of human knowledge, questioning what metaphysics can achieve as a science. He introduces the key distinction between analytic and synthetic judgments, wherein analytic judgments are true by virtue of their meaning while synthetic judgments add new information to our understanding. He then argues that certain synthetic judgments can be known a priori, that is, independently of experience.

Furthermore, Kant examines the possibility of synthetic a priori knowledge, which lays the groundwork for his exploration of the nature of human cognition in the Critique of Pure Reason . He also introduces the notion of space and time as a priori intuitions that structure our experience of the world.

Critique of Pure Reason

The Critique of Pure Reason is Kant’s magnum opus and his most significant and influential contribution to philosophy. In this monumental work, he aims to determine the scope and limits of human knowledge and to address the fundamental questions of metaphysics and epistemology.

He begins by exploring the nature of human cognition and the process of how we acquire knowledge, and argues that human experience is shaped and organized by the mind’s a priori categories (such as causality, substance and quantity), which are essential for making sense of the empirical world. He posits that space and time are not inherent properties of the external world but are rather the fundamental forms of human intuition, through which we structure our experience. Moreover, he introduces his theory of synthetic a priori judgments, which are crucial for understanding the foundations of mathematics and natural science, and thus provide essential insights into the nature of reality.

Kant asserts that while we can know phenomena – the appearance of things – through our cognitive faculties, the true nature of noumena – the things-in-themselves – remains beyond human comprehension.

Groundwork of the Metaphysics of Morals

In the “Groundwork”, Kant shifts his focus to moral philosophy and ethics. This work is a key pillar of his ethical theory and serves as a foundation for his later works on morality.

He begins by asserting the importance of a good will as the supreme moral principle, and argues that moral actions should be guided by the “Categorical Imperative”: a universal moral law that applies to all rational beings, which dictates that actions should be undertaken based on principles that can be consistently applied to all individuals without contradiction.

Moreover, he explores the concept of duty and highlights the idea that true moral worth lies in acting out of a sense of duty, rather than from self-interest. Moral actions, therefore, are not determined by consequences but by the intention behind the action. He asserts the autonomy of the moral agent, stating that individuals have the capacity to rationally determine their moral duties, and should act in accordance with the moral law.

Groundwork of the Metaphysics of Morals lays the foundation for understanding Kantian ethics: his views on autonomy, moral responsibility and the universal principles that guides ethical behavior, vis-a-vis, the categorical imperative.

Influence on Philosophy

Immanuel Kant’s critical approach to reason, exploration of the human mind and his rigorous examination of ethical principles had a far-reaching influence on the trajectory of western philosophy in the centuries that followed.

Two significant areas where Kant’s influence was particularly pronounced are German Idealism and the broader landscape of 19 th and 20 th century philosophy.

Kant’s critical philosophy served as a catalyst for the development of German Idealism, a philosophical movement that emerged in the late 18 th and early 19 th centuries. The German Idealists, including Johann Gottlieb Fichte , Friedrich Schelling and G.W.F. Hegel , built upon Kant’s ideas while also extending and transforming them.

Fichte, in his work Foundations of the Entire Wissenschaftslehre (1794), sought to address the gaps in Kant’s system and developed a more radical version of idealism known as subjective idealism. He argued that the self is the ultimate ground of reality, and the external world exists as a projection of the self’s consciousness.

Schelling, influenced by Kant’s emphasis on the unity of consciousness, developed a philosophy that sought to reconcile the divide between nature and spirit. In his System of Transcendental Idealism (1800), Schelling explored the notion of an absolute, which unites the subject and object and serves as the underlying principle of reality.

Hegel, arguably the most influential figure in German Idealism, took Kant’s dialectical method to new heights in his Phenomenology of Spirit (1807) and Science of Logic (1812-1816). Hegel’s dialectical approach involved the interplay of opposing concepts (thesis and antithesis) leading to a higher synthesis. He further developed the idea of absolute knowledge, a comprehensive understanding of reality that encompasses both the subject and object.

Beyond German Idealism, Kant’s ideas continued to resonate with philosophers and influence philosophical movements throughout the 19 th and 20 th centuries.

Existentialist thinkers, such as Søren Kierkegaard and Jean-Paul Sartre , engaged with the former’s ideas on individual autonomy and moral responsibility, as they explored the themes of human freedom, choice and the subjective experience of existence.

Phenomenology, a philosophical approach that originated in the early 20 th century through the works of Edmund Husserl and Martin Heidegger , and sought to investigate the structures of consciousness and lived experience, echoed Kant’s perspective on the role of the mind in shaping our perception of reality.

In the 20 th century analytic philosophers, such as Bertrand Russell and A.J. Ayer, in the context of epistemology and metaphysics, scrutinized Kant’s views on analytic and synthetic propositions and the nature of a priori knowledge. Their critical assessments and contributions to the ongoing debate illuminated the relevance of Kantian philosophy in the emerging analytic tradition, leading to a deeper understanding and refinement of the former’s views within the framework of modern analytic philosophy.

Immanuel Kant’s philosophy garnered both positive acclaim and critical scrutiny during his time and in the centuries that followed.

Kant’s philosophy was met with a sense of awe and admiration. His Critique of Pure Reason was seen as a watershed moment in philosophy, challenging traditional metaphysical assumptions and providing a new framework for understanding human knowledge. His perspective on the role of the mind in shaping perception and the introduction of synthetic a priori knowledge were seen as innovative concepts that expanded the horizons of philosophical inquiry.

Moreover, Kant’s moral philosophy, focused on the autonomy of rational agents, moral duty and the categorical imperative, was lauded for providing a robust foundation for ethical decision-making. His deontological ethics, grounded in reason and universal principles, resonated with many who sought a rigorous and rational approach to morality.

Despite the accolades, Kant’s ideas were not without controversy. One significant point of contention was the concept of transcendental idealism, as some critics questioned the nature of the noumenal realm, arguing that it remained an unknowable and speculative construct.

Furthermore, the categorical imperative faced criticism for its alleged rigidity and lack of consideration for the complexity of real-life moral dilemmas, as some argued that adhering strictly to universal principles could lead to morally counterintuitive conclusions.

Additionally, Kant’s complex writing style, especially in the Critique of Pure Reason , was criticized for its difficulty and abstruseness, as many readers found it challenging to navigate the intricate arguments and terminology, leading to diverse interpretations.

Immanuel Kant’s philosophical ideas, while influential, have not been immune to criticism and scrutiny. Two areas where Kant’s theories have faced significant objections are transcendental idealism and his deontological ethics.

Kant’s concept of transcendental idealism, which posits that our knowledge is limited to phenomena, the world of appearances, and that the noumena, the true nature of reality, remains unknowable, has been a subject of debate and criticism.

As Kant himself acknowledged that we can never directly access the thing-in-itself, this limitation has led some to question the validity of the distinction between phenomena and noumena, with some critics suggesting that it might be an unnecessary and unverifiable distinction.

Hegel’s philosophical system, known as Absolute Idealism, emerged as a response to what he saw as limitations in Kant’s ideology, as he sought to develop a more comprehensive and systematic approach, which he believed could resolve some of the perceived shortcomings in Kant’s philosophy.

Moreover, transcendental idealism has been challenged for potentially undermining scientific inquiry: if the external world is merely a construct of the mind, it raises doubts about the objectivity and reliability of scientific knowledge, which relies on the assumption of an independently existing external reality.

In this context, philosopher of science Karl Popper ‘s focus on empirical falsifiability offered a contrasting yet complementary view to Kant’s transcendental idealism. A scientific theory, according to Popper, is one that makes specific predictions that can be disproven through observation and experimentation – in short, it must be potentially falsifiable. These perspectives, Kant’s transcendental idealism and Popper’s falsifiability, significantly contribute to discussions about the nature of human knowledge and the boundaries of empirical investigation.

Kant’s deontological ethics, centered around the categorical imperative and the notion of moral duty, has faced objections on various fronts, as some argue that the focus on universal moral principles may lead to rigid and inapplicable conclusions.

Another point of contention is its lack of guidance in resolving conflicting moral duties when adhering to a universal principle may not provide advice on how to act, potentially leaving individuals without a solution.

Furthermore, kantian ethics has been criticized for not considering the consequences of actions, as solely focusing on their rightness based on intention or adherence to moral rules potentially overlooks the consequences.

In addition, some argue the intrinsic value of moral actions, regardless of their outcomes, might not fully account for the emotional and contextual aspects of ethical decision-making, neglecting the importance of empathy and compassion in moral judgments.

Subsequent philosophers have presented contrasting ethical theories, such as utilitarianism and virtue ethics, which take a more consequentialist approach to morality. Utilitarianism, proposed by John Stuart Mill , focuses on maximizing overall happiness and considers the consequences of actions to determine their moral worth. Virtue ethicists – inspired by Socrates , Plato and Aristotle – argue for the cultivation of virtuous character traits as central to ethical decision-making, affirming the importance of personal virtues in guiding behavior.

Moreover, the universalizability of moral rules has been met with criticism from communitarian thinkers, who contend that ethical principles should be situated within the context of particular communities and cultural traditions, challenging the universality that Kantian ethics upholds.

Immanuel Kant was a highly influential figure in Western philosophy, renowned for his innovate framework and unique perspective. His works in epistemology, metaphysics and ethics laid the foundation for a comprehensive philosophical system known as Kantianism, which played a crucial role in Enlightenment thought and continues to influence modern philosophical discourse.

Kant’s critical philosophy emphasized the role of human cognition in shaping our experience of the world and introduced the concept of a priori knowledge. In his work, “Critique of Pure Reason”, he argued that certain knowledge is inherent in the structure of the human mind itself, proposing that there are innate mental structures, such as space, time and causality, that shape how we understand reality. Knowledge, therefore, is not the passive reception of information from the external world, but is actively structured by the human mind.

Kant’s ideas on epistemology and metaphysics had a profound impact on subsequent philosophical movements, as the active role of human cognition influenced the development of idealism and transcendentalism, which sought to explore the relationship between the mind and reality. The notion of a priori knowledge also sparked debates on the nature of universals and the possibility of objective knowledge.

Kantian ethics, based on the categorical imperative, holds that moral actions should be guided by universal principles, emphasizing the importance of moral autonomy, reason and human dignity. Asserting that individuals should not treat others merely as a means to an end, but as ends in themselves, he proposed that people should act in a way that they would want everyone else to act in similar circumstances. His moral philosophy has had a lasting impact on ethical discourse, shaping discussions on the nature of moral responsibility and the foundations of ethical systems, and the notion of the categorical imperative has been subject to numerous interpretations and criticisms, leading to a rich tradition in Kantian ethics.

Kant’s enduring legacy is evident in the profound influence he has had on generations of scholars and the continued relevance of his ideas to contemporary philosophical inquiries. The Kantian system continues to be studied and debated by philosophers, providing valuable insights into the nature of knowledge, reality and moral reasoning.

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An Introduction to the Work of Kant

The philosophy of Immanuel Kant (1724–1804) can be divided into two major branches. His theoretical philosophy, which includes metaphysics, is based on the rational understanding of the concept of nature. The second, his practical philosophy, comprising ethics and political philosophy, is based on the concept of freedom. Both of these branches have been enormously influential in the subsequent history of philosophy.

Kant’s Critique of Metaphysics

In one of history’s best-known philosophical compliments, Kant credited the work of David Hume (1711–1776) with disrupting his “dogmatic slumbers” and setting his thinking on an entirely new path. To better understand the results of this new line of thought, we should briefly consider the “dogma” in question, and Hume’s attack on it. The prevailing philosophical orthodoxy in Kant’s time was a rationalism set out by Gottfried Leibniz (1646-1716), and systematized by Christian Wolff (1679–1750). According to such rationalists, empirical knowledge based on experience is suspect because it is necessarily tied to the subjective perspectives of individuals. Because the human senses are inherently fallible, empirical investigations can never reveal how the world really is, untainted by perspective: objective knowledge of the world can be achieved only through the use of reason. Leibniz, for example, provided an account of the world derived by reason from only two basic principles, which he believed were self-evidently true.

David Hume was an exponent of empiricism, a doctrine opposed to rationalism. For empiricists, all knowledge is derived from sense experience, and, therefore, the subjective perspectives of observers can never be entirely overcome. According to this position, rationalist efforts to circumvent the senses by relying on reason alone are bound to fail. Reason can contribute to knowledge, but only by relating ideas to one another, and ideas are ultimately based on sense impressions. An independent “realm of ideas,” or access to knowledge of reality untainted by the human senses, is therefore impossible. Hume was especially effective in drawing out the skeptical implications of the empiricist position. He argued that neither personal identity nor causality could legitimately be inferred from experience. Although we might notice that some events regularly follow others, we cannot infer that one caused the other. Kant found Hume’s attack on causality particularly worrisome, because it threatened the basis of modern natural science.

In his Critique of Pure Reason , Kant lays out his response to this philosophical dispute. Kant sees the force of the skeptical objections to rationalism and therefore aims to re-establish some of the claims of reason on firmer ground. Kant agrees with the empiricists that there is no “intelligible realm” accessible only by reason, and he denies that we can gain knowledge of how the world is, independent of all experience. However, he does not conclude that all human knowledge is ultimately reducible to particular experiences. For Kant, it is possible to draw general conclusions about the sensible world by giving an account of how human understanding structures all experience. As he puts it in the Preface to the second edition of the Critique:

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.

Kant compares his metaphysical studies to those of Copernicus, who revolutionized the study of astronomy by accounting for the position of the observer of the celestial bodies. Analogously, Kant aims to revolutionize metaphysics by accounting for the structure of the understanding that apprehends nature. According to Kant, the sensible world has certain features that can be known a priori , not because these are features of the objects in themselves, but, rather, because they are features of human understanding. We can know a priori that all objects will exist in space and time because these are the forms of our intuition; we could not even conceive an object that exists without these forms. Similarly, all experience is structured by the categories of the understanding, such as substance and causality. On the Kantian view, human understanding becomes the legislator of nature because the “laws of nature” that we perceive in the world are put there by our understanding.

In the Critique of Pure Reason , Kant aims to show the limits of what can be known by theoretical reason, and his strategy depends on a distinction between phenomena (objects as we experience them) and noumena (objects as they exist in themselves). In one sense, Kant chastens the ambitions of reason. Because all knowledge is structured by the categories of the understanding, we must forego knowledge of things-in-themselves. However, knowledge of these categories also allows us to draw a priori generalizations about the phenomenal world. For example, we know that the natural world is governed by the principle of causality because causality is a form of knowledge. By confining his conclusions to the world of experience, Kant is able to meet the threat of Humean skepticism and put natural science on a firm foundation.

Moral Philosophy

Kant’s understanding of moral freedom and of moral principles has been central to discussions of morality from his time forward. His moral philosophy is a philosophy of freedom. Without human freedom, thought Kant, moral appraisal and moral responsibility would be impossible. Kant believes that if a person could not act otherwise, then his or her act can have no moral worth. Further, he believes that every human being is endowed with a conscience that makes him or her aware that the moral law has authority over them. Kant calls this a “fact of reason,” and he regards it as the basis for a belief in human freedom. However, Kant also believes that the entire natural world is subject to a strict Newtonian principle of causality, implying that all of our physical actions are caused by prior events, not by our free wills. How, then, can freedom and morality be possible?

In simplified terms, Kant’s answer to this problem is that although humans are subject to causality in the phenomenal realm, we are free in the noumenal realm. To make sense of this answer, it is necessary to understand Kant’s distinction between theoretical and practical reason. The Critique of Pure Reason gives an account of theoretical reason and its limits. Theoretical reason can understand the natural world through the categories of the understanding. Practical reason addresses questions of how the world ought to be and tells us our duty. It also leads humans to a concept of an ideal world, which it becomes our aim to create. However, the proper functioning of practical reason requires the existence of certain conditions, such as God, immortality of the soul, and, most importantly, free will. Because none of these is contained within the categories of the understanding, theoretical reason can know nothing about them. However, argues Kant, because theoretical reason is also incapable of disproving their existence, we are justified in accepting their existence practically. As he puts it in the preface to the second edition of the Critique of Pure Reason , Kant “had to deny knowledge in order to make room for faith.”

According to Kant, ethics, like metaphysics, is a priori , meaning that our moral duty is determined independently of empirical considerations. Kant’s ethics can therefore be contrasted with ethical views such as utilitarianism that hold that the morality of acts is derived from their consequences. In the Groundwork of the Metaphysics of Morals , Kant outlines his fundamental ethical principle, which he calls the “categorical imperative.” The moral principle is “imperative” because it commands, and it is “categorical” because it does so unconditionally, that is, irrespective of the particular inclinations and circumstances of the actor. This moral principle is given by reason and states that we may act only in such a way that the maxim of our action, i.e. the principle governing our action, could be willed as universal law. For example, one is forbidden to act on the maxim “lie whenever it provides an advantage” because such a maxim would destroy trust among humans, and with it the possibility of gaining any advantage from lying. Those who act on non-universalizable maxims are caught in a kind of practical contradiction. In another formulation of the categorical imperative, Kant specifies that we must always respect humanity in ourselves and others by treating humans always as ends in themselves, and never merely as a means.

Freedom, for Kant, is thus not the “freedom” to follow one’s inclinations. Instead, freedom implies morality, and morality implies freedom. To act on one’s inclinations or desires, even if one desires the morally correct act, is to be determined by the causal forces of nature, and therefore to be unfree or “heteronomous.” To act morally is to act “autonomously,” meaning to act according to the law that one gives oneself. It is not sufficient only to perform the acts required by morality; it is also necessary to act intentionally in accord with one’s moral duty.

Political Philosophy

Kant’s political philosophy is entwined with his moral philosophy. Political activity is ultimately governed by moral principles based on human autonomy. Therefore, in his essay “On the Common Saying: ‘This May be True in Theory, But it does not Apply in Practice,’” Kant is critical of political thinkers, such as Machiavelli , who believe that amoral or immoral means are permissible in politics. Still, although Kant argues that morality is obligatory in politics, he does not believe that people’s actual political behavior is controlled by duty.

One of the most important political acts required by duty is the establishment of a state based upon law, a Rechtsstaat. In the Doctrine of Right (the second part of the Metaphysics of Morals ), Kant tells us that the only innate right is “freedom, insofar as it can coexist with the freedom of every other in accordance with a universal law.” Human freedom and dignity must be respected, and this is possible only within a constitutional state governed by law, which protects the civil rights of individuals. Kant differentiates “republics,” the kind of government he advocates, from “despotisms” according to whether their executive and legislative branches are separated from one another. When executive and legislative powers are invested in a single body, the government becomes despotic because law is no longer universal but is determined by a particular will. Direct democracies thus are inevitably despotisms because the majority oppresses the minority rather than acting according to universal law.

Kant’s emphasis on lawful government and civil rights connects him to the natural rights thinking of predecessors such as Hobbes , Locke , and Rousseau . However, Kant’s justification for the state is not limited to the justifications offered by these thinkers. Kant does not argue merely that individuals enter the state or social contract for prudential reasons, because their interests are best served by the state, but also that we have an obligation to respect human freedom, and this requires us to create a Rechtsstaat if one does not already exist.

Whatever the place of morality in politics, Kant sees that humans are governed by their inclinations and desires, which make them partial to themselves and dangerous to one another. Further, actual rulers often repress their subjects. Yet, despite the fact that actual governments often fall short of realizing the principles of right, Kant abjures the idea that subjects ought to revolt against existing governments to create more perfect ones. He regards any “right to revolution” as incoherent because states are the only existing embodiment of right. Instead, Kant argues that subjects always have a duty to obey their governments, though they may use their public reason to criticize them.

Kant’s political philosophy is characterized by a disjunction between the realm of political principle and the material motives of much human behavior. In order to draw these two together, he argues that it is precisely by means of humankind’s negative or asocial characteristics that societies are created and drawn closer to meeting the requirements of morality. As he puts in his essay “Perpetual Peace,” the problem of civil government can be solved even for a race of devils, if they be intelligent. Even the most self-interested actors will come to understand that a state is the best means of protecting their own interests against others, even if they would rather exempt themselves from the law. They would design institutions which could constrain all to obey the law and act as if they were governed by morality. In Kant’s words, the establishment of a lawful and peaceful state “does not require that we know how to attain the moral improvement of men but only that we should know the mechanism of nature in order to use it on men, organizing the conflict of the hostile intentions present in a people in such a way that they must compel themselves to submit to coercive laws.”

Kant’s views on international relations exhibit the same tension between principle and fact. Kant argues that a state of perpetual peace is required morally. However, such a state can only come about when a set of improbable political conditions take effect. For perpetual peace to occur, all states must possess a republican civil constitution, participate in a union of states, abolish standing armies, and refuse to take on national debts for war, among several other conditions. Although we cannot expect existing governments to establish these conditions merely from their own desires, a historical teleology exists (Kant argues) whereby they might come about nonetheless. War plays a central role in this process. It is under the threat of war that humans form governments, and find that republican constitutions are most effective in meeting internal and external dangers. Moreover, as individuals and states pursue their interests through the medium of growing commerce, they find that war is incompatible with profit. States will thus avoid war in order more effectively to pursue wealth. Part of the reason that the continued pursuit of self-interest promotes peace is that modernization and economic advancement will make wars so catastrophic in their effects and expensive in their conduct that states will become increasingly inclined to avoid them. We therefore come closer and closer to the condition of peace that morality enjoins.

Although political institutions are brought about by the wicked elements in the human constitution, Kant hopes that such institutions might have some rehabilitative effects on their subjects. As he writes in “Perpetual Peace”: “A good constitution is not to be expected from morality, but, conversely, a good moral condition of a people is to be expected only under a good constitution.” However, the gap between the ideal world of morality and the natural world of politics can never be closed completely. Kantian morality depends on intentions. If a race of devils act according to the law only because they are compelled to by their own interest, their state would not be a morally good one. They only act as if they are moral. Morality requires that one follows duty out of a will to do so. Yet, it is impossible, within the natural world, to distinguish with certainty between an individual who acts from duty and one who follows the law out of a natural inclination. Indeed, it is impossible to make this distinction with certainty in one’s own case. Nor is it possible to distinguish a state of firmly established perpetual peace from a temporary lull in international conflict. In spite of these limits, Kant argues that the mere possibility of perpetual peace and of the coincidence of happiness and morality is enough to oblige us to make these ideals our ends.

For further introductory reading, see also:

Richard Velkley,  Freedom and the End of Reason: On the Moral Foundations of Kant’s Critical Philosophy , Chicago: 1989.

Susan Meld Shell, Kant and the Limits of Autonomy , Cambridge: 2009.

• World Biography

Immanuel Kant Biography

Born: April 22, 1724 Königsberg, East Prussia (now Kaliningrad, Russia) Died: February 12, 1804 Königsberg, East Prussia German philosopher

The major works of the German philosopher Immanuel Kant offer an analysis of theoretical and moral reason and the ability of human judgment. He had a great influence on the intellectual movements of the nineteenth and twentieth centuries.

Childhood and education

The fourth of nine children of Johann Georg and Anna Regina Kant, Immanuel Kant was born in the town of Königsberg, East Prussia, on April 22, 1724. Johann Kant was a harness maker, and the large family lived a humble life. The family belonged to a Protestant religious group of Pietists (a German religious movement whose members strongly believed in religious experience and biblical study), and a concern for religion touched every aspect of their lives. Although Kant became critical of formal religion, he continued to admire the "praiseworthy conduct" of Pietists. Kant's elementary education was at Saint George's Hospital School and then at the Collegium Fredericianum, a Pietist school, where he remained from 1732 until 1740. Here he gained a deep appreciation for the classics of Latin literature, especially the poet Lucretius.

In 1740 Kant entered the University of Königsberg. He became interested in philosophy, mathematics, and the natural sciences. The death of Kant's father in 1746 left him without income. He became a private tutor for seven years in order to have enough time and money to continue his education. During this period Kant published several papers dealing with scientific questions. The most important was the "General Natural History and Theory of the Heavens" in 1755. In this work Kant concluded the origin of the solar system was a result of the gravitational (having to do with the force exerted between bodies of matter) connection of atoms (the smallest pieces of matter). In the same year Kant presented a Latin treatise, "On Fire," to qualify for the doctoral degree.

Kant spent the next fifteen years (1755–1770) as a lecturer. In order to live he lectured between twenty-six and twenty-eight hours a week. Despite this enormous teaching burden, Kant continued to publish papers on various topics. He finally achieved a professorship at Königsberg in 1770.

Critique of Pure Reason

At the age of fifty-seven Kant published the first edition of the Critique of Pure Reason (1781; 2d ed. 1787). This enormous work is one of the most important and difficult books in Western thought. The aim of the critique is to explain how experience and reason interact in thought and understanding. The Critique of Pure Reason is a methodology (a collection of methods and rules) of how "understanding and reason [the power of understanding] can know apart from experience." This revolutionary proposal means that the mind organizes our experiences into the way the world appears and the way that we think about the world. Any experience is placed into one of these categories so that it can be understood. Kant also wrote that the mind can have knowledge of things that have or have not been experienced, but these are only possibilities. Kant does not say that the mind creates objects—only the conditions under which objects are noticed and understood. We can never know noumenal reality (theoretical objects or ideas that are understood by thought alone) with any certainty.

Kant suggests that the theories of God, freedom, and immorality (something that goes against ideas or right and wrong) are not proved or disproved through the use of reason, nor can the use of scientific methods prove or disprove their existence. The idea of them is beyond the realm of human experience. Kant expressed that faith in God, freedom, and immorality are rational beliefs because their existence makes an orderly and moral world a possibility.

Later works

While theoretical reason is concerned with knowledge, practical reason is concerned with will, or self-determination. There is only one human reason, but after it decides what it can know, it must determine how it shall act. Thus the freedom of the will determines how one shall lead his life. And the basic, reasonable principle of a free morality (a morality that one is free to choose) is some universal and necessary law which follows. This principle is called by Kant the "Categorical Imperative," which states that a man should act in a way that is acceptable and applicable to all people. In questioning the outcome of man's freedom, Kant insists that practical reason assumes the immortality of the soul and the existence of God as the conditions for true freedom.

In 1790 Kant completed his third critique, which attempts to draw these conflicting ideas together. The Critique of Judgment attempts to connect the concepts of nature with the concepts of freedom.

Although Kant continued to write until shortly before his death, the "critical works" are the source of his influence. Only a life of extraordinary self-discipline enabled him to accomplish his task. He was barely five feet tall and extremely thin, and his health was fragile. Toward the end of his life he became increasingly antisocial and bitter over the growing loss of his memory and capacity for work. Kant became totally blind and finally died on February 12, 1804, in Königsberg.

For More Information

Kuehn, Manfred. Kant: A Biography. New York: Cambridge University Press, 2001.

Scruton, Roger. Kant: A Very Short Introduction. Rev. ed. New York: Oxford University Press, 2001.

Sedgwick, Sally, ed. The Reception of Kant's Critical Philosophy: Fichte, Schelling, and Hegel. New York: Cambridge University Press, 2000.

Stuckenberg, J. H. W. The Life of Immanuel Kant. London: Macmillan, 1882. Reprint, Lanham, MD: University Press of America, 1986.

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Notes to Immanuel Kant

1. The best biography of Kant, on which this section draws, is Kuehn 2001.

2. Kuehn 2001, 38, 44. See also 54.

3. On Kant’s intellectual development and pre-critical thought, see Walford and Meerbote 1992, Beiser 1992, Laywine 1993, Schönfeld 2000, Kanterian 2018, Allison 2020, and Kant, Immanuel: philosophical development .

4. Citations from Kant’s texts refer to volume and page numbers in the Akademie edition (see bibliography), except for references to the Critique of Pure Reason , which is cited by page numbers in the original first (A) and second (B) editions. All quotations from Kant follow, with some minor alterations, the English translations in The Cambridge Edition of the Works of Immanuel Kant (see bibliography). 

5. See Gardner 1999, chapters 1-2; and Beiser 2000.

6. Bird 2006, 31.

7. In the Prolegomena , Kant renames it “critical idealism,” but this name did not stick (4:293).

8. See also A369, which however occurs only in the first edition. For further discussion, see Kant, Immanuel: views on space and time .

9. Garve’s original review was drastically shortened, heavily edited, and published anonymously by Feder in January, 1782. Kant replied directly in the Prolegomena (4:372ff.). Both Garve’s original review and the version edited by Feder are translated and discussed in Sassen 2000.

10. Recent proponents of the two-objects interpretation include Strawson 1966, Aquila 1983, Guyer 1987, Van Cleve 1999, and Jankowiak 2017.

11. Recent proponents of the two-aspects interpretation include Bird 1962, Bird 2006, Prauss 1974, Langton 1998, Allison 2004, and Allais 2015.

12. For example, Bxviii–xix, A38–39/B55–56, A42/B59, A247/B303, A490–491/B518–519, and passages about the problematic boundary concept of noumena in the chapter on Phenomena and Noumena and at the end of the Amphiboly.

13. For examples and discussion, see Robinson 1994 and Ameriks 1992. See also Allison’s replies in Allison 1996, chapter 1.

14. For example, see Henrich 1969; Henrich 1976; Ameriks 1978; Guyer 1987, part II; Guyer 1992; Kitcher 2011; Longuenesse 1998; Longuenesse 2005, part I; Allison 2004, chapter 7;  Bird 2006, chapters 13–16; and Allison 2015. See also Kant, Immanuel: theory of judgment , Kant, Immanuel: transcendental arguments , and Kant, Immanuel: view of mind and consciousness of self .

15. See also A116 and Guyer 1987, 132–139.

16. In fact, these too are judgments, which in the Prolegomena Kant calls judgments of perception (4:298–299). But they are judgments about my subjective states rather than about objects distinct from me. As judgments they have a truth value: it is either true or false that I feel nostalgia when I see this house. Kant’s point, however, is that I can make such judgments about my own subject only if I also make judgments about objects distinct from me. Merely subjective judgments of perception are parasitic on objectively valid judgments of experience, because self-consciousness requires that I place myself in an objective world and refer at least some of my representations to objects distinct from me. See Beck 1978.

17. See A66–83/B91–116, B159, and Longuenesse (2006).

18. Kant calls space, in particular, an “ens imaginarium” or being of the imagination to emphasize that on his view we are not somehow conscious of the whole of space, which he also describes as “an infinite given magnitude” (292/B348–349, A25/B39). Rather, we are conscious of space only to the extent that we represent objects in it, but we must represent objects in a single space and cannot represent any boundaries of space. See Longuenesse 2005, chapter 3.

19. See Kemp Smith 1923, 2; and Kant, Immanuel: account of reason .

20. See Grier 2001, Rohlf 2010, Willaschek 2018, and Kant, Immanuel: critique of metaphysics . 

21. See Wood 1984, Allison 1990, and Allison 2020. Kant’s important discussions of freedom include not only the texts cited here from the Critique of Practical Reason , but also the third antinomy and its resolution in the Critique of Pure Reason and section III of the Groundwork .

22. For further discussion of Kant’s practical philosophy, see Kant, Immanuel: moral philosophy , Kant, Immanuel: and Hume on morality , and Kant, Immanuel: social and political philosophy .

23. See Rohlf 2010.

24. See Beck 1960, 244–45; and Wood 1970, 95–96.

25. See Silber 1959; Wood 1970, 94–95; Reath 1988; and Engstrom 1992, 776–777.

26. See Wood 1970, chapter 4; Guyer 2000, chapter 10; and Kant, Immanuel: philosophy of religion .

27. Rohlf 2008 develops another way of understanding this problem that emphasizes its moral significance for Kant.

28. See Ginsborg 1990, Guyer 1997; Allison 2001; Zuckert 2007; and Kant, Immanuel: aesthetics and teleology .

Copyright © 2020 by Michael Rohlf < rohlf @ cua . edu >

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