Oh, my point was that (for me) 'beauty' isn't a concept but just a token that gets bandied about. I have some faith that there is a concept behind the token when other people use the word, and I have used the word in contexts where I've estimated that the concept is somehow 'close enough' to what might be meant by beauty ... but simultaneously I'm aware I'm not communicating any specific concept and probably not communicating the one I intend.

Even a vague feeling could point to a concept. If you have a vague feeling about 'beauty' that could correspond to any of a myriad of different concepts, then that is probably a set. (The set of all things you do tie or would tie to that feeling at that moment.)

I'm liking the idea that any concept must point to an actual set, though, and I think I'll go with that definition in my thoughts from now on. So: a 'concept' is something in my brain that defines a set.

... But now it is time to go back to lukeprog's post and check what he meant by concept and start using that token with his meaning in this context..