[Part of The Molyneux Project; read the main critique here]
In an earlier post, I criticized Stefan for using the words "valid" and "rule" while talking about morality. I still think that Stefan's use of those words is somewhat unclear, but I want to take back the definitions I proposed of those terms. I was thinking in terms of formal logic when I wrote that post, and it's not fair to attack someone for using terms in another way, when the way Stefan used them was very similar to the way they're used in most other contexts. I maintain that Stefan's idea of a "valid concept" needs a lot of work, because I'm still not sure why he would use that term. But I withdraw my claim that Stefan commits any category error, because he would only be guilty of that fallacy if we accepted certain definitions of "concept" and "rule" which are not the only acceptable definitions. So I apologize to Stefan for the undue criticism, and I apologize to any other readers who didn't catch my mistake.
I just want to point out that this is a perfect illustration of why I'm hoping for criticism. This time I caught my own bad argument, but I'm sure that there are other problems with my reasoning which I haven't noticed yet. Please feel free to point out any weaknesses, even if you aren't sure that I'm wrong. Clarification is a good thing!