Groundwork for the Metaphysics of Morals – A Book Summary

There is something beautiful about Immanuel Kant’s book The Groundwork for the Metaphysics of Morals. Stylistically, it is dry and, by all accounts, it is over-complicated. But it has moments of clarity in which Kant’s moral edifice, his deontological ethics, loses its murk and becomes crystal clear, moments where his heavy and knotted penmanship adopts a light and untangled character that just gets to the point. We all know those “aha!” moments, those times when everything clicks into place and we feel as if we truly understand something. In Groundworks, I had four of those moments, each concerning a different foundational feature of Kant’s ethical theory. Through these four features, we can understand the essence of his argument.


Kant claims that because humans are rational beings, they have the freedom to act in accordance with either reason or inclinations. Because we are free to make this choice, morality can be seen as a command, or an imperative, that we chose one side and not the other, even though we can defy it.


So, which imperative is morally correct? Well, Kant is a rationalist, which means he believes the most accurate way to analyze and describe the world is through reason. He is also an absolutist, which means he believes that ethical rules must apply to all people, regardless of culture, religion, or any other differences.

So, the morally-correct imperative, that which ethically guides us to one road instead of the other, Kant feels, must be rationalistic and absolute. For Kant, this rules out the inclinations. They are empirical, gathered through experience and not reason, and also relativistic, thus subject to change and not absolute. Reason, however, is rationalistic and, so he claims, absolute, because it is universal, able to guide all rational beings to the same ethical conclusions.

Reason’s imperative is the categorical imperative, which is absolute, rationalistic, and good in itself. It instructs us to “do x,” period, requiring no other justification than to act for the sake of the law.

Inclination’s imperative is the hypothetical imperative, which is relative, empirical, and involves justification. It instructs us as “do x because of y.” That is, it instructs us to act for a certain reason or to get something in return. Acting this way, even if for the morally correct reason, is merely conforming to the law.


Thus, the morally correct imperative must be the categorical imperative, and the foundation of morality must be reason, because it is rationalistic and absolute.

This categorical imperative takes on two forms, from which the morality of all actions can be derived:

  1. Act only on the maxim that you can will to be a universal law
    • maxim is a guiding principle for your action. For instance, if your maxim for murdering a colleague is “because they were annoying,” then you must be willing to allow colleagues to murder you if you are annoying. Of course, a world where murder is justified by annoyance is clearly worse off than before, thus murder by this maxim is unethical, and you should not use this maxim unless you believe other should be able to use it against you or others.
  2. Act only so that you treat humanity as an end in themselves and not as a means to something else.
    • Kant claims that fellow rational beings are intrinsically valuable, that they are good in and of themselves.
      • Therefore, they must be treated by the categorical imperative’s command of “do x” (i.e. help your colleague, period; just because you should), which treats him as an end.
      • And not treated by the hypothetical imperative’s command of “do x because of y” (i.e. help your colleague to get on his good side so he’ll cover your shift), which treats him as a means to an end.
    • We also must not violate other rational beings’ ends. If your colleague is saving up money for retirement and you ask him for a thousand dollars,  saying that you’ll pay it back though you know you’re lying, then you’ve violated his ends.
      • Your deceit interfered with his freedom to use reason to make his own choice, and his ends of saving for retirement were affected. Therefore, you’ve violated this form of the categorical imperative and your action is unethical!
    • Also, note that Kant distinguishes between treating people as a means and treating them as a means only. We cannot help but treat people as a means (i.e. in school, we treat our professors as means for education, but they also treat us a means which ensures their employment–thus we are symbiotic, which is fine!). But treating one as a means only is unethical (i.e. marrying a much older, wealthy person for their money).


So, when at a crossroads between reason and inclinations, it is categorically imperative that we choose reason. In other words, it is our duty to choose reason, which Kant believes can always overpower inclinations, even if every fiber of our being feels otherwise. This is Kant’s ethical deontology, that is, his duty-oriented ethical theory.

Put another way, we are obligated, as fellow rational beings, to act only in ways that do not violate the two forms of the categorical imperative: acting only by a maxim we would will to be a universal law, and treating other rational beings always as ends in themselves and never means.

As you can guess, there is no better substitute for understanding a work as complex and nuanced as Groundworks than just reading it yourself. What I have described in a few pages, Kant describes in eighty. Clearly, much has been left out. But this is the essence of Kant’s book and his ethical deontology, and I hope you found it as interesting as I have!

Summaries such as this are great food for thought. However, the benefits of reading philosophy are almost entirely lost in them. The powerful insights and difficulty of these texts hone your abilities to think carefully, speak eloquently, dismantle other’s ideas quickly, and grow more knowledgeable. All of this is lost in summaries but the last. So, I urge you to pick up Groundworks and give it a read. It is categorically imperative!


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