I was wondering how Kant would respond to these sorts of questions.

  1. "Act only according to that maxim whereby you can at the same time will that it should become a universal law without contradiction."

But Kant himself was celibate! Why does it not follow that Kant must have desired the extinction of the human species?

  1. "Act in such a way that you treat humanity, whether in your own person or in that of another, always at the same time as an end and never merely as a means."

Is taking a taxi immoral? I am using a taxi service as a means to get somewhere.

  • This is really definitely two separate questions, any chance we could split them apart?
    – Joseph Weissman
    Dec 22 '14 at 17:42

There are two questions here.

Regarding the second, it's a simple error of interpretation. Kant says that you cannot use others as mere means. This means you cannot treat rational beings as merely the means to your ends not that you cannot enter rational agreements where they become the means to your ends.

Regarding the first, Kant addresses questions of sex in the Metaphysics of Morals (not the Groundwork) that is more commonly read. There he addresses it twice -- once in the Metaphysical Principle of Right (a.k.a. Doctrine of Right) and the other time in Metaphysical Principle of Virtue (a.k.a. Doctrine of Virtue).

To make a long story short, Kant finds a way to legitimate heterosexual sex in marriage. The elements are that:

  1. He believes all sex is use of another person as means
  2. He believes only marriage can enable you to consent to this sort of use as a contract for mutual use
  3. He recognizes the continuation of the species through procreation as an important way of keeping rationality in the world -- since we are rational creatures.

Through these three assumptions, he concludes that heterosexual marriage is okay if it procreative in intent.

Is this fully compatible with the first formulation of the categorical imperative that you quote? That's a good question. It seems incompatible on a first reading, but it's important to realize that the CI is a test of moral action and it's not clear that Kant prohibits action that is not immoral. So it could be that this falls into a dead zone.

You might also arguably be able to come up with a maxim that supports Kant's position and is universalizable. The challenge there is to define maxim of action, because there's very little clarity as to exactly what that is. Kant tells us it is a principle of will.

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