Hume asked the question how can one move from an 'is' to an 'ought' in his book, A Treatise on Human Nature:

In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary ways of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when all of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not.

Now, Kant acknowledges that Hume awoke him from his dogmatic slumber. He is also famous for his Categorical Imperative using which he places morality on a rational basis.

How does his Categorical Imperative tackle the Is-Ought problem? Or, does he simply side-step the whole issue?

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    Might want to say a few things about the categorical imperative, and give at least a hint of the connection you see between the is-ought problem and it. (I don't think there are any interesting connections between the two, because Hume's problem is a logical one, while Kant's solution is an moral/ethical principle.) Commented Sep 30, 2013 at 23:13
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    @Rostomyan: I didn't think that there was a direct connection as I implied in my question, but I wanted to check. The only connection I see is that Humes is-ought problem attacks the rational founding of morality, whereas Kant finds a rational basis on a different ground. altogether. Commented Sep 30, 2013 at 23:43

3 Answers 3


You've asked both how Kant approaches the Is-Ought problem and whether he does a good job with it. I'll give the outline of an answer to the first, and you can decide whether it side-steps the issue.

Kant works around Hume's problem by focusing on the idea of rationality. He argues that it is rational to act out of respect for duty and to respect rationality wherever it occurs. That is, his ending point is clearly at ought-statements, like that we ought to act out of respect for duty. The question is whether his starting point is merely descriptive—about what "is."

Rationality is a word or concept with not only a descriptive function but also an honorific function. Another word like this is "artistic." One the one hand, if I describe a painting as artistic, I'm simply saying that it's art. I'm making an "is" statement. On the other hand, built into the very idea of being appropriately called "artistic" is the idea of being (at least somewhat) good art. I would hesitate to call my sloppy napkin sketch artistic. This is the word's "honorific" function.

I point this out to suggest that Kant's concept of rationality may have normativity (or the idea of goodness) built right into it, in which case he doesn't so much move from "is" to "ought" as postulate a kind of "ought" people probably ought to accept (in so far as they want to be rational), and then argue that it implies some other "ought" statements.

That's the start of an answer. A great deal has been written on how Kant argues, and there are significant disagreements among experts about his strategy.

  • yes, I imagine a great deal has been written on this. That rationality has honorific value is this an insight that comes from viewing philosophy in an anthropological light - its where I would have generally associated ideas of honour systems. Commented Oct 3, 2013 at 14:32
  • Good question — "honorific" doesn't have anything directly with personal honor. The connection is just that both involve praising. The term "honorific" is a philosophical and linguistic way of describing words that not only describe but also praise something. Commented Oct 3, 2013 at 14:56

I would argue that Kant throws the question back onto the questioner. Human behavior can only be explained by supposing some of their actions are modeled after oughts rather than what is immanently reasonable; so how do you explain the fact?

For him all relations are the product of apperception; there are no causal relations, and there are no accidental relations, and there are no moral relations; there are only relations determined in apperception after logical possibilities grounded in the categories. All categorizations of relations into sets that are causal, accidental or moral are categorizations of apperceived relations. How those different sets are to be justified is what finds Kant sticking his head over the parapet of what is known in the understanding to gaze upon the transcendental realm; if morality is a fact and it requires a transcendental explanation then that is what Kant gives.

The transcendental explanation of the moral set is that my thing in itself meets a thing in itself in the noumenal realm and issues in the determination of my will by reason. Reason is involved because the transcendental realm is the absolute Idea or transcendental major premise and every logical possibility that can be syllogistically deduced from it. It is because I am free to disobey my initial will because phenomenally I don't understand why I should suffer that we can fall into the immorality.

But I think Mozibur is right. I know of no justification Kant gives that identifies the ought manifest in the noumenal realm with the categorical imperative we are supposed to wield in the phenomenal realm. How can Kant phenomenalize noumena?


You may like my answer to 'Why should people be moral...?'. I reference Alisdair MacIntyre's 1984 After Virtue, which places Kant after moral philosophers had discarded the notion of teleology as a valid or at least knowable domain. Here's p53:

Each of the three elements of the scheme—the conception of untutored human nature, the conception of the precepts of rational ethics and the conception of human-nature-as-it-could-be-if-it-realized-its-telos—requires reference to the other two if its status and function are to be intelligible.

If we can't know human-nature-as-it-could-be-if-it-realized-its-telos—or at least have an idea of it which is different from human-nature-without-tutoring, then ethics collapses as a concept in and of itself. It gets replaced with a [often masked] Nietzschean imposition of the will by a strict subset of society.

Kant tried to argue for a telos—his "Kingdom of Ends"—but he couldn't offer a reason why all rational human beings ought to pursue it (and in pursuing it, follow Kant's ethics). There's the question of whether we can accurately model human beings as 'rational', but is that the only question? For example, there are the problems that human beings have finite lifetimes and that some people will take advantage of any such "Kingdom of Ends" and thus need to be kept from making it worse than alternatives. How much do these distort the KoE?

Kant either didn't know of these problems, or decided that there was still enough of a telos (e.g. a community of people making rules everything would want to follow) in order to motivate his categorical imperative. Once you have a telos, that is your ought, and the only question left is how to get from here to there.

  • Doesn't answer the question directly. Also, rhetorical questions or questions in general tend to give the impression that your answer is incomplete.
    – iphigenie
    Commented Oct 7, 2013 at 22:19
  • @iphigenie: I added my best interpretation of Kant's view. Surely rhetorical questions are acceptable, for pointing out potential issues and further paths of inquiry?
    – labreuer
    Commented Oct 7, 2013 at 23:09
  • Good add, though I don't see the wish for a community with rational rules being enough of a motivation for the categorical imperative, that has still to be regarded as highest incitement when consequences and other persons are not taken into account. As of your claim that Kant might not have known about the problem of the is-ought-derivation, I would seriously doubt that and would appreciate any sources on that.
    – iphigenie
    Commented Oct 8, 2013 at 0:30
  • @iphigenie: To articulate, Kant thought he offered reasons but nobody buys them. Perhaps I should dig up some readings from a class I took on the matter. The stuff he didn't seem to know about where the questions I asked, not the "couldn't offer a reason" statement.
    – labreuer
    Commented Oct 8, 2013 at 1:18

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