The Ethicist’s Toolbox: Kant’s Categorical Imperative

How can I be a morally good person? This article explores the categorical imperative, one potential answer to that important question given by 18th-century philosopher Immanual Kant.

Apr 29, 2022By Amanda Adie, MA Philosophy

immanuel kant portrait pieter bruegel triumph ethics


When we are trying to decide what the morally right thing to do is, what should we take into account? Is it the consequences of the action that matter the most? Or, is it the intentions of the person we should look at? Both? Neither? One of the potential answers to these questions comes from an ethical theory put forth by 18th-century German philosopher Immanuel Kant. This theory proposes that it is not consequences that should guide our actions; rather, we should be concerned about acting rationally and in accordance with duty to moral principles. In this article, we will take a deeper look at Kant’s deontological theory of ethics and the categorical imperative — what it appears to get right, where it seems like it possibly goes wrong, and why we should still take it seriously in ethical philosophy.


Immanuel Kant, Inventor of the Categorical Imperative

groundwork metaphysics morals kant book
Title page of the Groundwork for the Metaphysics of Morals by Immanuel Kant, 1785


Immanuel Kant, the man responsible for the idea of the categorical imperative, was a German philosopher who wrote in the 18th century. His body of work spans a wide range of philosophical topics, including everything from metaphysics to aesthetics.


Kant’s influences included the likes of G.W. Leibniz and David Hume — the latter he credits for “interrupting [his] dogmatic slumber and gave [his] investigations in the field of speculative philosophy a quite new direction” (1772).


Kant’s Groundwork for the Metaphysics of Morals (1785) is the text that matters most for our discussion. In this work, he introduces us to his deontological theory of ethics, using rationality and the categorical imperative as the guide for moral action.

Get the latest articles delivered to your inbox

Sign up to our Free Weekly Newsletter


While Kant never traveled far from home and never married, he was still quite the social butterfly. His dinner parties were an event where people went to see and be seen, enjoy food and drink, in accordance with Kant’s strict rules.


That reminds me — you have a dinner date to get to!


Thought Experiment: A Dinner Date Dilemma

francis chapin studio party painting
Francis Chapin, Studio Party, n.d. Art Institute of Chicago


Imagine that you’re on a dinner date, and your date prepares a meal that smells and tastes like Michael Jordan’s gym socks. You can’t tell if it was the mystery meat or the sauce that is still ominously bubbling at you, but you do know if you will survive taking another bite.


Upon seeing your expression, the date asks, “Don’t you like it? It’s my great-grandmother’s secret recipe!”.


You have found yourself in an ethical dilemma. On the one hand, you don’t want to lie to your date! However, telling the truth is definitely going to hurt their feelings! You’ve recently taken an introductory course to ethics and have committed yourself to being a morally good person, but you’re still stuck. What is the right thing to do here?


Before we can answer that question, we will need to excuse ourselves from dinner and take a walk through Kant’s ethics. More specifically, we need to take an in-depth look at Kant’s categorical imperative and how it works to guide our actions.


The Categorical Imperative: 3 Paths to Moral Goodness

good deed never forgotten
A Good Deed is Never Forgotten by Pierre Nicolas Legrand, ca. 1974-5, via the Dallas Museum of Art


To determine whether some action is in accordance with our duties, Kant has a tool on his belt for us trying to act right — the categorical imperative. The categorical imperative can tell us which actions are morally permissible and prohibited.


There are three formulations of the categorical imperative:


  1. Maxim of Universalizability — act only so that you can will that it become a universal law for all.
  2. Maxim of Human Dignity — act only so that you always treat humanity as ends in themselves, never as a means.
  3. Maxim of Autonomy — act only as though you are motivated by your own rationality, not from outside external sources.


While all three are important, Kant wrote that the most fundamental maxim is the first one — the maxim of universalizability. For this reason, we can focus our attention on just this formulation of the categorical imperative without (much) worry of angering any Kantian apparitions.


According to the maxim of universalizability, we must take the action in question and translate the action into a maxim, a rule of action. From there, we then must imagine a world where all of humanity performs this action. Suppose it is the case that performing the action in our imaginary world would become logically impossible. This would mean that the action in question is morally wrong and, therefore, prohibited.


In other words, if the action ceases to exist due to being universalized, the action is prohibited. If the imagined world is just unpleasant or difficult due to universalizing the action, then you are in the clear!


Thought Experiment: The Moment of Truth

william frith lovers painting
William Powell Frith, The Lovers, 1855, Art Institute Chicago


Now, let’s get back to our dinner date. Remember, your date has served you a very special dinner that tastes and smells like feet. At this point, you are worried that the heap on your plate is achieving sentience.


They’ve asked if you like their meal, and you have to choose whether to tell the truth or to lie. You want to do the morally right thing. Time to reach for the toolbox and get out your categorical imperative!


First, we take lying and turn it into a maxim; in simpler terms, a rule of action. Something like, “it is morally permissible to use language in a way that does not correspond to the truth of reality, to further some goal”.


Next, we must ask ourselves if our rule of action can be universalized. To lie, we depend on others using language to communicate meaningfully. When I tell a lie, I both depend on and undermine the meaning of language to gain something for myself or others.


So, if all people began using words to communicate in a way that does not correspond to the truth, language would lose meaning. In this world, meaningful speech would cease to exist, and we could not lie even if we wanted to! In our imagined world, lying has become logically impossible.


Therefore, you cannot respond to your date’s question with a lie. The morally right thing to do is tell your date that you don’t like the food they’ve made.


Of course, you can leave out that it tastes like Michael Jordan’s gym socks and just say you don’t particularly like the dish — but only if you are so inclined!


Universalizing Some Other Morally Questionable Actions

marcus stone stealing keys painting
Stealing the Keys, Marcus Stone, 1866


Since you are likely not going on another date after that whole dinner date disaster, you have some time to go over a few more cases and see how they fare after applying the universalization formulation of the categorical imperative!


Let’s take the following three actions and universalize them:


  1. Stealing
  2. Murder
  3. Getting a tattoo


Starting with the action of stealing, imagine that you are at a candy store. You are filling a bag with the 10 cent candies. No one is looking. Would it be so wrong to throw in a couple of extra sweets? Can this small act of theft be universalized?


Well, a rule of action for stealing would be something like “it is morally permissible for me to treat all property as though it were my own, to further my own goals”. By stealing, I am treating someone else’s property as if it were my own.


To steal an object, we both depend upon and undermine the existence of property. So, when we try to universalize stealing, this action would actually cause all property to no longer exist. We would live in a world of community objects, where no person “owns” any object, meaning that stealing would become impossible. Universalizing stealing makes the act of stealing cease to exist and is thus prohibited.


Now let’s universalize murder. A rule of action for the act of murder would be something along the lines of “it is morally permissible for me to treat some other person’s life as something not worthy of continuing, for my own goals”. Not surprisingly, universalizing murder creates a world where humanity no longer exists. After some time, all humans will eventually be murdered, making murder impossible. This means that murder is not permitted.


pieter bruegel triumph death painting
Pieter Bruegel’s The Triumph of Death, 1562, in the Mudeo del Prado


Finally, let’s take a look at something a little bit different: getting a tattoo. When we make a rule of action, something like “it is permissible for me to treat my body as a canvas for artwork, for my own gain”. This one is actually pretty tricky.


It seems as though if we universalize the action, there isn’t a case of logical impossibility generated. Everyone could get tattoos, and the act of tattooing would still exist. If you run out of room, you can always change up some colors or tattoo on top of the previous work. It might not look pretty, but it isn’t impossible, and that is what matters.


According to the universalization formulation of the categorical imperative, getting a tattoo seems like it should be permitted. However, it isn’t clear that you aren’t somehow treating yourself as a means rather than an end in itself. Kant would surely say that tattoos are not permitted via the second formulation, but it isn’t totally clear if he is justified in this assertion by his own theory of ethics!


Some Criticisms of Kant’s Categorical Imperative

immanuel kant portrait painting
Portrait of Immanuel Kant, via Wikimedia


As we saw above, there are some squirrelly cases where we can easily assume that Immanuel Kant would believe an action to be prohibited by the categorical imperative: e.g. tattoos, masturbation, online pornography. However, it doesn’t seem that the first formulation of the categorical imperative actually prohibits these actions.


Sure, we can easily apply the other formulations to get the prohibition, but universalization is supposed to be the most fundamental! If it is the most fundamental, then shouldn’t it be sufficient for our purposes here without trying a different formulation?


Another critique of Kant’s ethics is that it is cold and disregards the significance of care. In the name of acting morally, Kant’s ethics guide us to perform actions that seem unkind or even downright cruel. In the grand system that is Kant’s entire body of philosophy, the individual and context-sensitive scenarios are all grouped together.


Kant’s categorical imperative tends to miss the nuances of love and human relationships, which is ultimately what ethics strives to make good.

Author Image

By Amanda AdieMA PhilosophyAmanda is a writer and philosopher. She holds an MA in Philosophy from the University of Wisconsin-Madison, with a primary interest in aesthetics, ethics, and the places where they overlap. She is passionate about teaching to children with developmental disabilities and helping make philosophy more accessible to those not in academia. When she is not writing, she can be found reading spicy romance novels, playing a halfling bard in her D&D group, or doing yoga.