Every sufficiently smart person who thinks about Kantian ethics comes up with this objection. I don’t believe it’s possible to defend against it entirely. However...
After all, Kant universalizes “I will deceive this murderer so he can’t find his victim” to “Everyone will deceive everyone else all the time” and not to “Everyone will deceive murderers when a life is at stake”.
That may be what Kant actually says (does he?) but if he does then I think he’s wrong about his own theory. As I understand it, what you’re supposed to do is look at the bit of reasoning which is actually causing you to want to do X and see whether that generalizes, not cast around for a bit of reasoning which would (or in this case, would not) generalize, and then pretend to be basing your action on that.
In the example you mention, you should only generalize to “everyone will deceive everyone all the time” if what you’re considering doing is deceiving this person simply because he’s a person. If you want to deceive him because of his intention to commit murder, and would not want to otherwise, then the thing you generalize must have this feature.
Similarly, I might try to justify lying to someone this morning on the basis that it generalizes to “I, who am AlephNeil, always lies on the morning of 13th day of March 2011 if it is to my advantage” which is both consistent and advantageous (to me). But really I would be lying purely because it’s to my advantage—the date and time, and the fact that I am AlephNeil, don’t enter into the computation.
Every sufficiently smart person who thinks about Kantian ethics comes up with this objection. I don’t believe it’s possible to defend against it entirely. However...
That may be what Kant actually says (does he?) but if he does then I think he’s wrong about his own theory. As I understand it, what you’re supposed to do is look at the bit of reasoning which is actually causing you to want to do X and see whether that generalizes, not cast around for a bit of reasoning which would (or in this case, would not) generalize, and then pretend to be basing your action on that.
In the example you mention, you should only generalize to “everyone will deceive everyone all the time” if what you’re considering doing is deceiving this person simply because he’s a person. If you want to deceive him because of his intention to commit murder, and would not want to otherwise, then the thing you generalize must have this feature.
Similarly, I might try to justify lying to someone this morning on the basis that it generalizes to “I, who am AlephNeil, always lies on the morning of 13th day of March 2011 if it is to my advantage” which is both consistent and advantageous (to me). But really I would be lying purely because it’s to my advantage—the date and time, and the fact that I am AlephNeil, don’t enter into the computation.