Scott - To be clear, I'm actually sympathetic to natural law theory. I ask these questions not in the spirit of trollish criticism, but out of the desire to learn more about the theory. If I sound like I don't understand what I'm talking about, then please help me understand 

And I sincerely apologize if you found the bumping rude - it's the first time I've encountered that reaction to bumping in all the years I've participated in threads. 

You say 'subversion' means 'using that faculty in a way that makes it weaker and less effective in achieving its end'. This seems strange - exercise can make a muscle temporarily weaker, and using your leg as a table leg makes it less effective, but we agree it isn't wrong to do those things.

You also give a second construal of subversion: 'A frustration or subversion of the faculty of locomotion would be some way of objectively trying to walk that nevertheless deliberately prevented you from walking effectively.' This seems more plausible, will think about it. Thanks!

Btw, I'm still not sure why we can't talk about the frustration of the natural end of organs. Feser speaks of organs too, after all. For example, he writes: 'Natural law theory does not condemn using a natural capacity or organ other than for its natural function, but only using it in a manner contrary to its natural function, frustrating its natural end.'

DanielCC - I'm actually sympathetic to natural law theory. I just don't understand it fully, which is precisely why I'm asking these questions - I want to learn more about it 

Jeremy Taylor - Intuitions are fair game in philosophy. Think of thought-experiments which elicit various intuitions. E.g. one cannot object to the Gettier cases by saying "We have a theory of knowledge which shows that these cases are cases of knowledge." Do you have the intuition that Pruss's counterexample is permissible?

DanielCC - I'm not sure about that, Feser writes: "To choose in line with the final causes or purposes that are ours by nature is morally good; to choose against them is morally bad." He speaks of moral goodness and badness, not rationality and irrationality. 

In any case, if frustrating an organ's function doesn't suffice for immorality, what does?

Why can't scientists temporarily turn off a subject's sense of smell to study the interaction between this sense and other senses, or the subject's psychological state? There doesn't seem to be anything wrong or 'perverted' with doing so.