I have a question regarding Kant's deontological Maxim of both Perfect and Imperfect duties.

What I know about them is that Perfect duties require a person to perform a certain "action" all the time, while Imperfect duties require a person to do that "action" sometimes.

Could someone please help define the duties in layman's terms, and the difference? It's getting more confusing. Thanks!


Kant raises a distinction between what he calls perfect duties and imperfect duties in the Groundwork of the Metaphysics of Morals and again in the Metaphysics of Morals: Doctrine of Virtue. You have the basic definition in hand: a perfect duty is one which one must always do and an imperfect duty is a duty which one must not ignore but admits of multiple means of fulfillment.

Kant specifies two imperfect duties: the duty of self-improvement and the duty to aid others. To understand why Kant thinks of these as imperfect duties, we need to first understand the nature of duty for Kant. The literature on this is vast, so I'm going to skip over some parts of the mechanics and summarize it as follows: a duty is something that we are obligated to by the Categorical Imperative. In other words, it is something that that we can see as a universal rule for all of humanity necessary for a morally just society (mixing together all three major types of formulations of the Categorical Imperative).

It's difficult to come up with completely non-problematic duties due to some issues related to the basis on which we act "maxims" and the means through which we universalize these, but I will skip over this for the purposes of this question (If interested, I suggest reading Allen Wood's Kant's Ethical Thought).

Let's say that I want to lie to someone. If we universalize this, then every rational creature will lie whenever it is convenient. This will turn out to be self-defeating because no one will believe what anyone says. Since we have a constant need of truth in our dealings, this is something we must practice at all times. (i.e., we cannot add an exception "except when telling the truth is inconvenient). This makes this a perfect duty in the Kantian system. Most perfect duties turn out to be negative duties -- i.e. don't do X. On Kant's system, every rational being is obligated by perfect duties.

Imperfect duties reflect the nature of human rational existence. We are born weak and frail, we cannot do everything by ourselves, and we die. These realities create interesting non-rational features of our reality: I needed someone to feed me when I was a baby. I need someone to help me when my car is stuck. I need a surgeon when my liver fails. These needs are not universal either in time or duration nor are they purely rational laws. To make these desires moral, Kant needs us to universalize them. Thus, we transform I need help at times into every [limited] rational creature has a duty to help other rational creatures at times. Thus, I have a requirement to aid others at times reflective of my own need for help at other times. This is one of the two imperfect duties for Kant.

The second imperfect duty is to perfect myself. This duty arises because when I need help, I need experts. Thus, the only way that rational creatures can have their needs met is if rational creatures are developing their talents. So, I too have a need to develop my talents in order to create a universalizable rule that would make it so aid is available when I need it of sufficient ability.

Moved to the level of the particular, imperfect duties are things like: study chemistry, practice the violin, learn Japanese, volunteer at an orphanage. These are duties I don't need constantly and that I somewhat pick from among. Thus, they are imperfect duties since they are not constant obligations, but they remain obligations.

What Kant does not answer is how often. He puts this question somewhat in the Doctrine of Virtue. You can read more about this in Creating a Necessity out of Virtue by Nancy Sherman.

I also gave a more thorough argument for this account in my dissertation.

  • Why do you think that practising the violin should be among the imperfect duties? Or is it so that the duties which are not perfect are of the other type; namely, imperfect? Jul 2 '18 at 9:22
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    Adeel Ansari - learning any skill is an imperfect duty because self-improvement is an imperfect duty. But part of how imperfect duties work is that they don't specify precisely what you need to do or even how frequently just that you have the task of improving yourself and helping others...
    – virmaior
    Jul 2 '18 at 9:28
  • virmaior - So, it doesn't specify anything about the object matter of improvement. I mean, for example: improving yourself in thievery; or helping others in thievery, or in killing time by practising, or helping others with, something not very useful, or useless altogether. Jul 2 '18 at 11:07
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    (1) improving in thievery would not be acceptable because thievery violates a perfect duty towards others.
    – virmaior
    Jul 2 '18 at 12:17
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    (2) the ways you improve yourself don't have to be moral per se but i guess they do need to have some potential for helping others (which perhaps you're questioning with respect to playing the violin?) But it doesn't have to be undertaken with the specific conscious understanding that it will definitely be used to help others -- just that it could in some conceivable way do so.
    – virmaior
    Jul 2 '18 at 12:18

I do not agree that perfect duties, for Kant, are those which you must always do, while imperfect duties are duties you don't always have to fulfill. This way of putting the distinction encourages people to accep the view of Kant as an absolutist in the sense that he does not allow exceptions to moral rules. This interpretation renders Kant's theory useless in attempting to deal with moral issues involving conflicts of duties. Kant defines perfect duties as those not allowing any exceptions to the inclinations. He does not say that they allow of no exceptions at all. In the introduction to the Meta. Of Morals Kant allows that when "grounds of obligation conflict,one cancels the other one out, in whole or in part." The essay ,"On the alleged right to lie from beneficent motives" which also seems to support the absolutist view, concerns the matter of how the law can respond to a lie intended to save an innocent person, but it does not state clearly that it would be immoral to lie, except in a merely. formal sense.

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    This seems to be intended as a comment on my answer. I think you're grossly misinterpreting the cancellation there. You're taking it to mean that the two somehow coalesce. I take it to mean on the contrary that since the Categorical Imperative is only one (Cf. Groundwork) that it eliminates all apparent conflicts leaving only your real duty.
    – virmaior
    Feb 9 '15 at 6:56
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    In terms of the reading you are giving On a Supposed Right to Lie, that's the same interpretation Korsgaard gives it. But I take that reading to be thoroughly convoluted. It defies the logic of Kant's empirical/noumenal distinction which undergirds the senses in which legal (Recht) and moral (Tugend) obligations differ. Specifically, the problem is that you're suggesting morality should be more lenient than law for Kant whereas I take Kant to believe that law restricts those outward actions that are always immoral and morality requires a correspondence of will to the moral law.
    – virmaior
    Feb 9 '15 at 6:58
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    Or to make a third point, the claims about obligations obliterating other obligations instanter seems to ensure there are not cases where Kant would believe our duties conflict.
    – virmaior
    Feb 9 '15 at 7:00

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