Let’s use the famous example. Kant argues that lying is categorically bad because, even though lying can be good in narrow circumstances, one cannot will lying to be okay in a universal way.

However, it seems to me that this argument will break down if we are allowed to consider more refined conditional statements, such as whether it is morally okay to “lie if it saves a life and doesn’t cause any other negative consequences”. I don’t see how one cannot will that to be a universal rule.

Therefore, it seems that much of the peculiarities of Kant’s theory end up deriving from the need to only consider a small set of simple rules, such as “whether lying is okay”. Thus, my questions:

  1. What motivates Kant to restrict himself to small set of rules?
  2. In Kant’s theory, what is the mechanism that decides which rules should be considered?
  • One of Kant's points is that you can never know that it "doesn’t cause any negative consequences", and you are always responsible for any consequences of a lie. Hence you can not rationally will it. "It is still possible that, after you have honestly answered “yes” to the murderer's question as to whether his enemy is at home, the latter has nevertheless gone out unnoticed,... but if you had lied ... then you can by right be prosecuted as the author of his death...", see What is the basis for Kant's misquote?
    – Conifold
    Commented Aug 22, 2020 at 10:05
  • Maxims have to be general to a great degree to count as maxims. Too specific a maxim would be like an axiom proclaiming an extremely specific fact about a certain location and event. I'm not saying Kant is a clear master of his own technique but there is a rhyme to his reason 😂 moreover, the simple "what if everyone did that" model of categorical imperative tests has to be adjusted to Kant's twelvefold categories of freedom. Commented Aug 23, 2020 at 15:18
  • @Conifold I understand this point. However, I do have to say it is rather weird as an argument against consequential thinking, as it effectively ignores probabilities. Relatedly, I do find a general tendency for philosophers to not incorporate probabilities into their theories but rely on “absolute things”. Are you familiar with how philosophers deal with probabilities?
    – J Li
    Commented Aug 23, 2020 at 21:31
  • There was little probability theory to speak of in Kant's time, and he was an absolutist even aside from that. I think, the appeal of his ethics even today is that it is based only on things that we can directly foresee and control rather than on gambling on what might or might not happen, which many find morally distasteful and which creates more opportunities for weaseling. McCarthy has a chapter on Probability in Ethics that takes a positive view.
    – Conifold
    Commented Aug 23, 2020 at 22:25
  • @KristianBerry I understand. I guess my question can then be rephrased to say: what motivates the need to look for maxims? Why not a much broader set of rules? What is attractive about general maxims relative to a large set of rules?
    – J Li
    Commented Aug 25, 2020 at 18:38

4 Answers 4


Welcome, J Li

It isn't strictly true that Kant focuses on a relatively small set of principles when discussing morality.

It is true that in the Groundwork of the Metaphysic of Morals (1785) he discusses only four examples to illustrate and tentatively vindicate his ethical theory. But Kant's discussion of morality is by no means confined to this brief text. In the Metaphysics of Morals (1797) he ranges over a broad variety of ethical topics - moral examples - from commerce and property, marriage, friendship, humility and hypocrisy, lust, money, murder, prostitution, gambling, punishment and public executions, revenge, and the distribution of wealth - among many other topics.

So why only four examples in the Groundwork- the ban on (1) suicide and (2) false promises, plus the requirement (3) to develop our talents and (4) at least on occasion to help others?

Kant is not a revisionary ethical theorist, unlike (say) the early utilitarians such as Bentham. He takes morality as he finds it, or as he believes it is, and undertakes to show that his categorical imperative test as applied to maxims produces results that agree with ordinary moral thinking. He takes such agreement as criterial for the correctness of his ethical theory.

The criticism has often been made, and rightly, that ordinary moral thinking, even in the form in which Kant conceived it (heavily influenced by German Protestantism), was more flexible about making a false promise than Kant recognises in the Groundwork.

The major point is, however, that Kant needed to test his ethical theory against ordinary moral thinking, since he was trying to theorise morality as it was or as he believed it to be. He took it to involve at least four prohibitions as basic - to oppose suicide, making false promises, failing to develop one's talents, and never helping others. Applied to the maxims of one's actions, the categorical test precisely (as Kant thought) ruled out all four prohibitions of ordinary moral thinking.

He regarded this as strong prima facie evidence that he had in his ethical theory, with its doctrine of the categorical imperative, captured cornerstone requirements of ordinary moral thinking. Remember, the Groundwork of the Metaphysic of Morals was just that - only a Groundwork. The heavy duty work of a comprehensive ethical theory was reserved mainly for the much later Metaphysics of Morals.


I. Kant, Groundwork of the Metaphysic of Morals, tr. M. Gregor & J. Timmerman, rev. ed., Cambridge: CUP, 2018.

I. Kant, The Metaphysics of Morals, tr. M. Gregor, rev. ed., Cambridge: CUP, 2017.

O. O'Neill, Constructions of Reason, Cambridge: CUP, 1989.

  • Geoffrey - this is one of the best answers I’ve ever encountered on Kant, putting him into historical context and explaining that he aimed to have a theory that “match data”. This aligns with my personal understanding of Kant as well. Thanks again.
    – J Li
    Commented Aug 26, 2020 at 2:37
  • J Li: Thanks for your very kind remarks. I am glad to have been of help. All the best - Geoffrey
    – Geoffrey Thomas
    Commented Aug 26, 2020 at 7:59

Kant wasn't interested in morality as it pertains to the outcomes of special cases; he was looking for a system of morality which leads to universal truth. To that end only the most general rules should be considered under the categorical-imperative. In your example of lying, under Kant's philosophy lying cannot be judged to be categorically good just because you're lying to certain people or telling certain lies. Kant doesn't make a utilitarian distinction here because he asserts that morally wrong actions can lead to good outcomes, but that doesn't make them categorically good. For instance, it's impossible to really know the outcome of your actions, but you can know the moral weight of the action itself. To answer your questions:

what motivates Kant to restrict himself to a small set of rules?

Kant restricts himself to rules which he can establish with his categorical-imperative. In doing so, he asserts that those rules can be considered universal ethics.

what is the mechanism that decides which rules should be considered?

Kant purposefully selects rules which we already intuitively know and seeks to prove why they are true. His writings don't preclude other rules from being considered.

  • It seems that Kant's method can also make a judgment on more refined rules such as "lying is okay if it is done with the intention (not consequence, and thus not consequential) to save a life". Therefore, this rule should also be considered universal ethics according to Kant?
    – J Li
    Commented Aug 21, 2020 at 22:37
  • I think Kant isn't concerned with intentions, either. He is concerned with the actions in and of themselves. Lying is bad, according to Kant, in and of itself, and intentions and outcomes don't affect the morality of it. Keep in mind that Kant was also coming from a Christian perspective.
    – Reifier
    Commented Aug 22, 2020 at 0:02
  • Are you saying that under Kant’s method, only actions can be judged? If so, of course, then what I proposed is out of the “set of things for consideration”.
    – J Li
    Commented Aug 22, 2020 at 7:18

It is hard for us to accept Kant's "deontic" ethics today, and it is admittedly hard to apply in practical cases. First, we have to recall that Kant was an Enlightenment thinker and scientist, yet also Christian in a largely Christian era.

Like many at that time, he was deeply concerned with the undermining of common morality by atheism, skepticism, and science. On what basis can we say some action is right or wrong? Isn't it all relative? Doesn't it all depend on what you want or on social consensus?

Kant, like many others, didn't like where this led, and we might say the 20th century would bring plenty of supporting evidence. He wanted to discover some deontic yet rational basis for morality beyond faith and moral duty "because God says so."

At the same time, he wanted to demonstrate the problems inherent in merely "hypothetical" or utilitarian imperatives: "Do this IF you want that." In this kind of morality the end implicitly justifies the means, making it easy to rationalize any action by the outcome or, failing that, our good intentions.

While Kant recognized that we can mathematize cause and effect in the natural world, he thought that human freedom and the very capacity for moral choice precluded this in the human realm. Even a computer can make "moral judgments" if we program it with the desired ends. As free, rational, moral beings we must transcend this whole mechanistic way of judging, we must recognize some good that is good in itself, apart from intended outcomes inevitably based on partial knowledge.

But what can that possibly be? If we can no longer accept "God says so," then is lying or propaganda, murder or mass murder, stealing or expropriation all okay, depending on the personal or social ends and our retroactive intentions? Kant's categorical imperative was an attempt to refute this in a way fully compatible with reason, yet arriving at the basic "golden rule" morals commonly supported by faith.

Today, we live in a world that is full of the unintended consequences of "good intentions" and purely scientific principles, not to mention genocides justified by the "betterment" or purification of society. How can one prove to the sceptic or nihilist or opportunist that some actions are wrong, "no matter what." This was Kant's aim. Once he arrived at the CI as a kind of rational necessity he saw no need to list endless examples any more than Euclid would.


First response to a question here, I hope it is of some value and is coherent enough for this space.

The rules Kant focused on is one factor. The method of testing a rule is where Kants best deonotological insight was. Namely the categorical imperative.

I often find the best way to learn something is to just show it.

"First, formulate a maxim that enshrines your reason for acting as you propose. Second, recast that maxim as a universal law of nature governing all rational agents, and so as holding that all must, by natural law, act as you yourself propose to act in these circumstances. Third, consider whether your maxim is even conceivable in a world governed by this law of nature. If it is, then, fourth, ask yourself whether you would, or could, rationally will to act on your maxim in such a world. If you could, then your action is morally permissible.

If your maxim fails the third step, you have a “perfect” duty admitting “of no exception in favor of inclination” to refrain from acting on that maxim (G 4:421). If your maxim fails the fourth step, you have an “imperfect” duty requiring you to pursue a policy that can admit of such exceptions. If your maxim passes all four steps, only then is acting on it morally permissible." - SEP Kants Moral Philosophy

Let's utilise the Kantian method to examine two possible principles people have been observed to live by.

The Principle of non-violence. The Principle of defense.

The principle of non-violence fails the third step. Even if I could trust that every human will be non-violent, I can't trust that of other forms of life. I can't even be non-violent to plants if I want to live. Letting myself die could be thought of as an act of violence against myself.

In contrast, the principle of defense passes all steps. I can will myself to act on it, I can rationally expect others to act on it either for themselves or others. I can generally expect that most forms of life will act in self defense or defense of something other than themselves.

That's obviously just the deontological side of it though. The consequentialist might argue that it would be wrong to defend someone while giving them time to be the instigator in a murder. Some would even argue it might be wrong to defend a murderer from direct retribution from the victims family.

In conclusion: I think Kants best insight wasn't really his own views on any one rule or sets of rules, but in how to even evaluate one rationally. Still, nothing's perfect.

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