Professor Christine Korsgaard’s work on Kant is fascinating. Her writing is exceedingly clear and rigorous. In contrast, a lot of writing on philosophy is frustrating because it not only pretends to be rigorous and fails, but also because it intentionally tries not to be clear. I don’t want to pick on anyone whose fans might come after me so I’ll pick on the Tao Te Ching, which opens with the following:

The Tao that can be told is not the eternal Tao.
The name that can be named is not the eternal name.

I think too much is written in this spirit.

When I first learned about Kant in college, his infamous position on lying to the murderer at the door was presented as obviously wrong. The categorical imperative was also presented as nothing more than a slightly dressed up Golden Rule. We were told that Kant said that an action was immoral when to universalize it would lead to a contradiction. No one bothered to explain how exactly one would go about proving such a contradiction.

Lying, they said, would lead to some sort of contradiction, because in a world where everyone always lied, the rule “you should lie to get what you want” would be logically contradictory (why?). Trying to carve out exceptions for specific lies would not make sense because such distinctions were not categorical but hypothetical. But in order to speak a lie I have to position my mouth in a certain configuration and emit air. Likewise, in order to continue living I need to breathe in and out. Why not say that to breathe in is immoral because in a world where everyone always breathed in and never breathed out we would all asphyxiate? And when I consider the moral value of lying, why is the act of lying considered more relevant than the act of exhaling air?1

All this left me with the impression that Kant was simply deluded and that it wasn’t worth trying to find any rigor in his arguments. But years later, a friend convinced me to give Kant another go and I found Prof. Korsgaard’s writings. I was blown away in particular by her work on making rigorous Kant’s tests for contradictions in conception and contradictions in the will in “Kant’s Formula of Universal Law” (1985). She tackles the question of “what is a contradiction” head-on:

In this paper I am concerned with identifying the sense in which there is a “contradiction” in willing the universalization of an immoral maxim, and especially with the sense in which the universalization of such a maxim can be said to have a contradiction in it - that is, with the idea of a contradiction in conception. There are three different interpretations of the kind of contradiction Kant has (or ought to have) in mind found in the literature.

  1. The Logical Contradiction Interpretation. On this interpretation, there is something like a logical impossibility in the universalization of the maxim, or in the system of nature in which the maxim is a natural law: if the maxim were universalized, the action or policy that it proposes would be inconceivable.
  2. The Teleological Contradiction Interpretation. On this interpretation, it would be contradictory to will your maxim as a law for a system of nature teleologically conceived: either you are acting against some natural purpose, or your maxim could not be a teleological law. The maxim is inconsistent with a systematic harmony of purposes, or with the principle that any organ, instinct, or action-type has a natural purpose for which it must be the one best suited.
  3. The Practical Contradiction Interpretation. On this interpretation, the contradiction is that your maxim would be self-defeating if universalized: your action would become ineffectual for the achievement of your purpose if everyone (tried to) use it for that purpose. Since you propose to use that action for that purpose at the same time as you propose to universalize the maxim, you in effect will the thwarting of your own purpose.

The more of her paper that I quote here the better this post will be just by virtue of diminishing the fraction of it that was written by me. I really recommend you read as much of Prof. Korsgaard’s work as you have time for!

But I wanted to write this post to jot down an idea whose precise form I haven’t seen discussed before. Namely, I think that the practical contradiction interpretation of Kant’s idea of a contradiction in conception in particular has an interesting relationship with the idea of the prisoner’s dilemma. I’d like to expand on this more in a later post, but for now it’ll suffice to say that in the prisoner’s dilemma the maxim “I will defect to end up better off” is clearly self-defeating if universalized: if all prisoners defect, none will end up better off. Thus the maxim has a contradiction in conception, and the prisoners in the dilemma have a perfect duty not to defect, assuming the practical contradiction interpretation.2 This is not even considering whether such a maxim has a contradiction in the will, in which we find an even greater parallel to payoff matrices.

I have seen arguments that Kant argues for cooperation in the prisoner’s dilemma because of the Formula of Humanity, or that the prisoners do not have a perfect duty because to consider the consequences of defection (“I will defect to end up better off”) renders the maxim non-categorical and therefore morally irrelevant (White, 2009).

But these seem to take for granted the same non-rigorous definition of contradiction that frustrated me when I first learned about Kant in college. To be frank, I find the question of what makes an action categorical vs. non-categorical distinction less interesting than the question of what makes a maxim contradictory precisely because we can more rigorously attempt to define the latter. I find the idea that contradiction in a rigorously Kantian sense is at the core of tragic game theoretic outcomes intriguing. That being said, please note that I am neither a trained philosopher nor familiar enough with Prof. Korsgaard’s work to make statements with any authority: I speak only for myself.


Later I learned that this problem has already been exhaustively studied and is called the “problem of relevant descriptions” (Schumski, 2017).


From p. 22-23 of Korsgaard (1985):

On the Practical Contradiction Interpretation, such a contradiction in the universalization of an immoral maxim is exactly what the test shows. In the world of the universalized maxim, the hypothetical imperative from which the false promiser constructs his maxim is no longer true. It was “if you want some ready cash, you ought to make a false promise.” But at the same time that he employs this hypothetical imperative in constructing his maxim, he wills its falsification, by willing a state of affairs (the world of the universalized maxim) in which it will be false. In that world, false promising is not a means to getting ready cash. Kant, therefore, not only has a specifically practical sense of “contradiction”, but should be seen as employing it in his contradiction tests.