This week's column is about an idea, an event, and a piece of sponsorship -- and the implications of these for Australian letters and debate.

The idea is the "public sphere" and the event is #twitdef, or the legal threat to sue for defamation issued against Australian academic Julie Posetti by the editor of The Australian, Chris Mitchell. The sponsorship is the $500,000-a-year deal by sandstone university lobbyists the Group of Eight.