"Who said we're not on Earth?" He looks at Chuck expectantly. Dean doesn't know if he's totally sure, but this place looks and feels like Earth, other than the weirdass shit; all the things in the houses? Totally Earth-y, and all the plants and food check out. The way the scientists were talking about potentially using the people with powers since they don't have any on their world -- could be Earth.

None of it's conclusive, but if he's not sure, then other people can't be either, unless they know something he doesn't.