Immanuel Kant was one of history’s most important philosophers, a broad-minded thinker who reconciled divergent strains of thought and influenced every generation of thinkers to come after him. He’s best remembered for his moral and epistemological ideas (more on that later), but he also set the stage for the rise of psychology, anthropology, and modern neuroscience. The modern scientific conception of cognition is largely an outgrowth of Kant’s philosophy. He even developed an early theory on the causes of earthquakes!
Modern students are split on whether Kant’s system is actually internally consistent or whether it contradicts itself. Kant studied so many different areas, weaving so many diverse ideas into a single philosophical system, that his philosophy is extremely multifaceted. But that same broad-mindedness also brought Kant into disagreement with himself! To take a few examples: Kant was intensely rational, but also intensely interested in psychology and the human experience; he argued that objective truth was real, but at the same time that it was indeterminate; he saw morality as grounded in total abstract rationality, but at the same time he recognized that human rationality was limited by the innate constraints of the human mind. For some students, this is evidence that Kant is grappling with the nuances and paradoxes of the real world; for others, it’s evidence that he was a confused, ultimately incoherent thinker. As you read about Kant’s thought, you can decide for yourself whether those apparent contradictions are strengths or flaws.
Immanuel Kant was one of the key philosophers of the Enlightenment period, alongside Thomas Jefferson in America, Voltaire in France, and David Hume in Scotland, all of whom lived around the same time. Kant was a generation younger than Hume and Voltaire, and got his education when the Enlightenment was already in full swing. He was spurred into philosophy by reading the work of David Hume, whose keen logical mind had produced extremely inventive critiques of prevailing notions of selfhood and causality. “I freely admit,” Kant would later write, “that it was the remembrance of David Hume which, many years ago, first interrupted my dogmatic slumber.” That’s high praise for a philosopher – before I read Hume, Kant is basically saying, I had no idea how to think for myself. Like other Enlightenment philosophers, Kant was interested in the ideas of freedom, reason, and individual liberty, and skeptical of traditional religion.
Kant lived in the German-speaking region called Prussia in northern Europe. He spent his whole life in the city of Königsberg, barely traveling beyond the city limits but constantly reading works by philosophers in other countries. He was born to a working-class family – his father was a harness maker who didn’t have much money. But a local pastor recognized Kant’s talents at a young age and got him an opportunity to study philosophy at Königsberg University. That was where Kant first learned about the Enlightenment and turned his attention toward philosophy, ultimately earning a PhD. He supported himself by tutoring the children of wealthy neighbors, and wrote philosophy in his spare time.
Before Kant, the philosophical world was split into rationalists, who believed that truth was determined by pure deductive logic, and empiricists, who believed that truth was determined by experiences. The two schools of thought had very different theories on how the human mind worked. For the rationalists, the mind had an innate capacity for apprehending reason, shown in our ability to learn universal truths about mathematics and geometry. For the empiricists, there was nothing innate about the mind at all – they saw the mind as a blank slate that learned from the world of sensory experience.
Kant argued that they were both right. He developed a mixed theory on the functioning of the human mind as both a rational and empirical organ. That theory has become so influential in modern psychology that it seems almost obvious: of course, we now say, the mind is both rational and empirical. But at the time it was revolutionary.
Kant saw the mind as an organ that soaked up sensory experiences and turned them into ideas (which was like the empiricists), but he also argued that the ordering of that experience was governed by inherent biases and constraints (which was like the rationalists). For example, he argued that the human mind has an innate conception of linear causality – event A happens, which causes event B to happen. We don’t actually see the causality. What we see is event A, followed by event B happening. But the mind is inherently biased to see the two events as connected, and so we infer causality from our experience. The modern scientific method is based on the assumption that these kinds of biases exist in the human mind, and that we need to correct for them using controlled experiments and careful measurement.
“Freedom,” Kant said, “is constraint by norms.” What a weird thing to say. Isn’t freedom the absence of constraints? Not according to Kant. Kant argued that all actions are constrained: the question is what they are constrained by.
In some cases, our actions are constrained by causes. If you try to fly out of a window, your action will be constrained by the causal power of gravity. If you try to rob a bank, your action will be constrained by the causal power of armed police.
In other cases, our actions are constrained by norms, or ideas. Say you’ve promised your roommate that you won’t eat the last slice of pizza. The roommate is gone for the night, so there’s nothing causally constraining you from breaking your promise. Kant says you should not break your promise because it’s an expression of your freedom: you become free by allowing your behavior to be constrained by moral principles even in the absence of causal constraints.
And here’s the kicker: Kant argued that if you do break your promise, then you are causally constrained. Your freedom to do the right thing was constrained by the causal power of your own desires! Kant saw emotion and desire as causal forces just like gravity or a police barricade. They arise from within, but that makes no difference to Kant. They’re still blunt causes, and to act in accordance with blunt causes is to be unfree. So if you do whatever you want all the time, you’re just a slave to your own impulses. But if you adhere to strict moral discipline, then you are a slave only to principle and therefore truly free.
So if you want to be free then your behavior should be constrained by moral principles (norms) and not by causal forces. But that raises an important question: how do you know what moral principles to follow?
Kant argued that we could ground morality in absolute reason – an idea he called the categorical imperative. It works like this:
That’s a little abstract, so take it back to the example from the previous section: you’ve promised that you won’t eat the last slice of pizza, but now you want it. Should you break your promise? Here’s how the categorical imperative would guide you through that decision:
The reasoning is important here: the reason you should keep your promise is not because God will punish you; it’s not because you want to maintain a friendship with your roommate; and it’s not because everyone will be happier if you control yourself. It’s not for any practical reasons. It’s pure rationality that makes the broken promise immoral. If everyone broke promises all the time, then the very idea of a promise would cease to have meaning.
Here’s another way to think about it. It’s tempting to think of the categorical imperative as a version of the Golden Rule, but it’s actually quite different. The Golden Rule is about individual compassion – putting yourself in someone else’s position and treating them as you would want to be treated in those circumstances. But that sort of individual compassion is too much of a personal, emotional basis for moral reasoning. Kant believed that morality should be founded on absolute reason, with no room for an emotional experience like compassion.
Instead of compassion, the “greatest good,” or the Golden Rule, the categorical imperative says that our behavior should be constrained only by pure rationality.
The categorical imperative was one of Kant’s most celebrated ideas, but has also turned out to be one of his most controversial. The categorical imperative is clear and concise, but it has a serious problem: a lot of people argue that it doesn’t actually tell us anything about morality. Imagine you’re in a conversation with a Nazi. The Nazi believes that might makes right – the strong should rule, and the weak should submit to the will of the strong. If a strong person wants to murder or steal from a weak person, then they should just do it. The only moral righteousness lies in physical power.
Is this person violating the categorical imperative? Is it irrational for them to wish everyone would act in this selfish, power-hungry way? You might very well say that their wish is hateful, or that it would lead to bad consequences, but the categorical imperative strictly bars us from taking those things into account. In the earlier example, it’s wrong to break your promise because doing so would destroy the very concept of a promise. But if the Nazi acts on the principle of strength, would that destroy the very concept of strength? Probably not.
In short, it’s hard to see how logic alone could prove the Nazi wrong – yet most of us are pretty sure that Nazism is immoral. So maybe Kant was wrong in trying to ground morality solely in logic.
On the other hand, if we ground morality in the emotions, doesn’t it all become shaky, indeterminate, and personal? Is there any way to avoid sliding into moral relativism if we remove the requirement that only logic can dictate morality? Modern philosophers are still grappling with these questions, and they probably will be for a long time to come.
“Act in such a way that you treat humanity, whether in your own person or in the person of any other, as a means to an end, but always at the same time as an end.” (1785)
Kant argued that morality meant recognizing the innate value of each person. The categorical imperative was meant to be a way of honoring that value – when you follow the categorical imperative, Kant said, you act in the way that everyone, rationally, ought to act. That means recognizing that you have to follow the same rules as everyone else rather than using other people to achieve your own selfish goals.
“Out of the crooked timber of humanity, no straight thing was ever made.” (1784)
Before Kant, many philosophers were theorists of perfection – they wanted to arrive at perfect reasoning, perfect truth, or perfect morality. But Kant was one of the first to fully recognize the inborn limitations of human beings. Modern cognitive neuroscience would say that human beings are born with brains that evolved over hundreds of millions of years to solve specific problems in specific ecological contexts – and in the end we can only think the thoughts that fit the limited capacities of our brains. Kant, of course, didn’t have all that science to back him up, but he did have strong intuitions and good arguments to suggest that humanity was a “crooked timber,” and that all of our philosophy would therefore be crooked in the same ways.
Kant’s moral philosophy had an intense focus on rules instead of outcomes. He argued that the ends never justify the means, even if the ends are extremely important. This kind of rule-based morality (philosophers call it “deontology”) plays an important role in superhero stories.
Batman, for example, has a rule against killing his enemies – even when doing so would save dozens of lives. In movies like The Dark Knight, Batman has plenty of opportunities to kill the Joker, and he knows that doing so would prevent the Joker from committing more murders. But he has a rule against killing (possibly rooted in the categorical imperative) and therefore can’t do it.
In some stories, deontology marks the hero. In other stories, it marks the villain. In the thriller Phone Booth, for example, the villain is a sniper who threatens to kill random people over minor moral transgressions. He argues that the world would be a better place if others stood up for justice the way he does – but his demands are unreasonable and his actions are way out of proportion to his victims’ crimes. He believes he’s following a kind of categorical imperative, but it has clearly led him away from the moral path.