Kant was a German philosopher born in 1724 in Konigsberg, Prussia. He is best known for taking up the challenge presented by the Scottish philosopher Hume as to what exactly we can know as human beings. What are the limits of reason and human knowledge? Kant presents what he declares to be a “Copernican Revolution” of the mind, explaining that the mind is not a “blank slate” receiving knowledge from the outside world, but rather the mind itself is programmed such that it structures our experiences in order make them meaningful and to make knowledge possible in the first place. He will distinguish between how things appear to us (phenomena) from their true nature (noumena), of which we can never know. He will also distinguish between judgments that are based on sensory experience (aposteriori) and judgments that are (apriori), and use this distinction to critically analyze metaphysical concepts such as the idea of God, the soul, immortality, and free will. Kant also famously puts forth the ethical belief that one should only act in a way that they would be happy if everyone were to act in the same way, known as the categorical imperative.
A professor of philosophy, Kant says that Hume “interrupted my dogmatic slumber, and gave my investigations in the field of speculative philosophy quite a new direction.” Hume was an empiricist, believing that all knowledge comes originally through sensory experience. Hume explained that things such as space and time did not really exist, but were concepts that the mind employed in order to make sense of reality. Likewise, Hume pointed out that there are no such thing as “real” causes and effects. Rather, causality is simply a mental construct which allows us to understand things in predictable and practical way. Kant embraced this insight, and made it the basis for his philosophy. While Hume had came to the depressing realization that as human beings we can never have true knowledge of reality since we are trapped inside our own minds, Kant strived to elaborate precisely what we can and cannot know, and how knowledge is possible, given the situation.
In the 16th century, the Copernican Revolution took place when the astronomer Copernicus showed that the planets orbited around the sun, which is the center of our universe. Before Copernicus, the apparent motion of the planets had convinced people that the Earth was the center of the universe. Copernicus was able to explain how this apparent motion of the planets was possible using a heliocentric (“sun-centered”) model. Since the Earth is also in motion, he recognized that the apparent motion of the planets must take into account not only their trajectories but also the fact that as observers we are situated on a constantly rotating surface (i.e. Earth). In the same way, Kant recognized that in understanding our experience of things, we must acknowledge that the mind is not merely a passive thing (a “blank slate”), but rather an active thing which influences how we experience things.
Kant wrote an extraordinarily difficult text, The Critique of Pure Reason, where he explains what we can know as human beings and how such knowledge is made possible in the first place based on the structure of his minds. Kant explains that we do not experience “things-in-themselves” (noumena), but rather only things as they appear to us (phenomena). Our mind is constantly perceiving the appearance of things, however, all of this input would be meaningless if our mind’s didn’t have some way of structuring the experience. Kant explains that the mind does in fact have the ability to structure our experiences so that they are meaningful and coherent to us. He explains that the mind intuitively structures our experience of things in terms of time and space. Without thinking about things in spatial terms, we wouldn’t be able to show relationships, and likewise without thinking about things in terms of time, we wouldn’t be able to understand things as happening in sequence. Kant explains that our mind is therefore preprogrammed to structure our experience in terms of space and time so that we can understand things in a meaningful way.
In addition to time and space, Kant explains that the mind has other categories which it employs in structuring our experiences. For example, as humans we see things in terms of “cause” and “effect” (causality). Kant explains that the reason we consider somethings causes and other things effects is because this allows us to make sense of the world. There is practical value in looking at the world in this way, and our minds work in such a way that we will be able to successfully navigate through life. Likewise, another of these categories is substance. Kant explains that when we see something, we assume that there is something there which is responsible for our experience. Therefore, the mind is structured such that we assume that things exist.
Because we cannot know things-in-themselves (noumena), but only as they appear to us (phenomena), Kant explains that we can not know things such as God, the world, or the self. He explains that these are ideas which we have created based on our experiences, but just because they are ideas that does not mean that they exist. He uses this point to critique Christian philosophers such as Anselm and Descartes who argued that God must exist since we have the idea of God. Likewise, Kant explains that we do not know knowledge of our true selves, but only the unity of experience which we have access to.
Kant believes every time we make a statement about something, we are making a judgment. He therefore strives to clarify the difference between different types of judgments. First, he distinguishes between analytic and synthetic judgments. Analytic judgments are those where the predicate is contained in the subject. For example, “All bachelors are unmarried.” In this way, analytic judgments don’t tell you anything new, but simply make explicit what was originally implied. Another example is that “A triangle has three sides.” Kant explains that a judgment is analytic when it’s negation would create a logical contradiction. For example, to say that “A triangle does not have three sides” would be a contradiction, therefore the statement is analytic.
Synthetic statements, however, are different in that they add new information. For example, “The man is wearing a hat.” Here, the predicate “is wearing a hat” is being added to the subject “the man.” The predicate is giving us new information which may or may not be true. If I negate this statement and proclaim, “The man is not wearing a hat,” this does not create a logical contradiction. Therefore, this statement is synthetic rather than analytic.
Kant then makes a further distinction between judgments which are independent of sensory experience (apriori) and those which are dependent on sensory experience (aposteriori). For example, the statement 2 + 3 = 5 is apriori because it is independent of sensory experience. Even if there was no one to make this statement, it would still be true. In contrast, the statement that “The car is red” requires that I have a sensory experience which confirms this is really the case. Kant makes these distinctions in order to explain how the mind structures our experience.
Realizing that a judgment can both synthetic (i.e. combining two different things) as well as apriori (i.e. not dependent on the senses), Kant posits that the mind structures our experience using these sort of “synthetic apriori” judgments. For example, he has shown that the mind uses the “category” of causality to allow us to experience things in terms of cause and effect. Kant recognizes that the statement “every change is preceded by a cause” is actually a “synthetic apriori” judgment. He explains that what happens is that we have a certain number of experiences, and from these experiences, we can either conclude that “every change is preceded by a cause” or alternatively conclude that “every change is not preceded by a cause.” Since this is a synthetic statement, either option is possible. The mind chooses to embrace the synthetic apriori statement that supports causality because of the benefit it gives us in terms of experiencing the world in a meaningful way.
Kant also uses this concept of synthetic apriori statements to critique the metaphysical claims of philosophers and theologicians. He recognizes that in the history of philosophy there has been endless debate as to whether the world is infinite or finite, whether it has a beginning in time or whether it has always existed, and other such questions. Kant explains that these are “antinomies,” meaning that because they are synthetic apriori statements, both the position the statement expresses as well as its opposite can be logically proven. For example, in order for the world to have come into being there must be a first cause, however, since everything has a cause there can’t be a first cause and therefore the world must have always existed.
Kant was hoping that by explaining the limits of human knowledge, he could put an end to the constant debating about metaphysical questions which are beyond the limits of our ability to know. (Kant shortened his Critique, infamously difficult to read, into the Prolegomena to Any Future Metaphysics in order to make it more accessible). Having explained what we can know and how human knowledge is possible, Kant recognized that there are still beliefs worth having as human beings despite these beliefs not being based on absolute certainty. In his Critique of Practical Reason, Kant explains that certain beliefs, such as a belief in God or the afterlife, can be a good thing since they give people the strength to persevere in the face of adversity. Or, as is the case with free will, there are certain beliefs which are necessary simply to get through life. In this way, Kant recognized that there is a practical aspect to reason as well, and that there are truths of the heart as well as the mind.
In addition to his theory of knowledge, Kant is famous for his ethical theory. He believed that morality is based not on what you do, but on having a good will. Further, Kant believed that to have a good will doesn’t mean to want to do good, but to do good because it is one’s duty. Kant explains that while it is nice if someone wants to do good, this does not make it moral because “the maxim lacks the moral import of an action done not from inclination but from duty.” Kant therefore sees morality not based on what happens as a result of one’s actions, or doing things out of the goodness of your heart, but rather following the duty which he believes we all have based on what he calls the “moral law.” Things are done because they are right and for no other reason.
He explains that we are able to know what is right because what is right is apriori i.e. not dependent on sensory experience. What is right must be something that is right universally i.e. right at all time in all places. Therefore, Kant comes up with what he calls the “categorical imperative,” which states that you should only do something if you would want everyone to do it. For example, since I wouldn’t want everyone to lie, therefore I shouldn’t lie. In this way, Kant has come up with a clear-cut way of determining for any action whether it’s “moral” or not.
Kant would also write a Critique of Judgment, where he explains the value of the beautiful or “sublime” which can be experienced in nature, transcending our conceptual understanding of everyday things. Later in life, he would criticize religion in his work Religion within the Mere Reason, as well as put forth a vision of himself as a citizen of the world (cosmopolitan) and suggest the creation of a League of Nations. Ironically, Kant basically never left his hometown of Kronigsberg all his life. Nevertheless, Kant would become the best read German philosopher in Europe, and represents a turning point in the history of modern philosophy. Representing a synthesis between the sense-based empiricists of Locke, Berkeley and Hume and the principle-based rationalists Descartes, Spinoza, and Leibniz, Kant created a synthesis in what he called his “transcendental philosophy.” His insights will pave the way for developments in the 19th century as varied as Kierkegaard, Marx, and Freud.