I've said this in a comment at rosania.org, but I think it bears repeating here: this is why we need a #blank? or #null? protocol that user classes can participate in as part of core. #nil? and an inextensible FalseClass just aren't enough to do the sorts of thing that Avdi was trying to do in his original post. My tentative proposal is languishing here: http://redmine.ruby-lang.org/issues/5372