would cast doubt on his or her own ability to understand anything about the planet. They would categorize things differently, in ways humans wouldn't think of. Yet if they were truly post-modernists, they would also recognize the validity of earthlings' claims on their reality as much as their own. They would realize that things that don't make sense to them make sense to people on Earth, in other words, that there is not an objective reality. In fact, I think this question is an interesting thought experiment to get at the essence of post-modernism. (If such a thing as an "essence" exists, post-modernists would question whether it does).