I should be able to view Things with lower permissions than I actually have

(User Story, Investigate , Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Security, Publication
Summary: In other words, "As the Owner of the Space, I should be able to look at Things as if I were a member of the Public".
This is probably some sort of mode on the Session, changing the way things are filtered.
It might be good enough to just say "I should be able to view things as Public" -- while the general case is the ideal, I suspect that in practice this is the use case that actually matters, and it may be much easier to implement the specific version.
This story is marked as part of Publication, because it is most interesting for Publishable Spaces.